Ionic Equilibrium. Contents. Theory Exercise Exercise Exercise Exercise Answer Key

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1 Ionic Equilibrium Topic Contents Page No. Theory 0 - Exercise - - Exercise Exercise Exercise Answer Key 3-33 Syllabus Ionic Equilibrium Solubility product, common ion effect, ph and buffer solutions; Acids and bases (Bronsted and Lewis concepts); Hydrolysis of salts. Name : Contact No.

2 IONIC EQUILIBRIUM Strong electrolytes : (i) Those substance which are almost completely ionize into ions in their aqueous solution are called strong electrolytes. (ii) Degree of ionization for this type of electrolyte is one i.e.. eg. HCl, H, NaCl.HNO 3, KOH, NaOH, HNO 3, AgNO 3, Cu, etc. Means all strong acids and bases and all types of salts. (i) Weak electrolytes : Those substance which are ionize to a small extent in their aqueous solution are known weak electrolytes.eg. H O, CH 3 COOH, NH 4 OH, HCN, HCOOH, Liq. SO etc. Means all weak acids and bases. (ii) Degree of ionization for this types of electrolytes in <<<. DEGREE OF DISSOCIATION When an electrolyte is dissolved in a solvent (H O), it spontaneously dissociates into ions. It may dissociate partially ( << < ) or sometimes completely ( ) Eg. NaCl + aq Na + (aq) + Cl (aq) CH 3 COOH + aq CH 3 COO (aq) + H + (aq) The degree of dissociation of an electrolyte () is the fraction of one mole of the electrolyte that has dissociated under the given conditions. No. of No. of moles dissociated moles taken initially For a weak electrolyte A + B dissolved is water, if is the degree of dissociation then AB (aq) A + (aq) + B (aq) initial conc C 0 0 conc-at eq. C( ) C C Then according to law of mass action, K eq [A ][B ] C.C C dissociation constant of the weak electrolyte [AB] C( ) ( ) [C V, then V /C(volume of solution in which mole is present) is called dilution, so K eq ( )V IONIC EQUILIBRIUM_ADVANCED #

3 If is negligible in comparison to unity then, ~. So K eq C K eq c V K eq. concentration { Thumb rule } ACIDS BASES AND SALTS : Arrhenius concept : Arrhenius Acid : Substance which gives H + ion on dissolving in water (H + donor) eg. HNO 3, HClO 4, HCl, HI, HBr, H, H 3 etc. Types of acids H 3 BO 3 is not Arrhenius acid. H + ion in water is extremely hydrated (in form of H 3 O +, H 5 O +, H 7 O + 3 ) and high charge density. The structure of solid HClO 4 is studied by X-ray, It is found to be consisting of H 3 O + and ClO 4. HClO 4 + H O H 3 O + + ClO 4 (better representation) Arrhenius base : Any substance which releases OH (hydroxyl) ion in water (OH ion donor) Types of base OH ion also in hydrated form of H 3 O, H 7 O 4, H 5 O 3 First group elements (except Li.) form strong bases. Bronsted - Lowery concept : (Conjugate acid - base concept) (Protonic concept) Acid : Substances which donate H + are Bronsted Lowery acids (H + donor) Base : Substances which accept H + are Bronsted Lowery bases (H + acceptor) Conjugate acid - base pairs In a typical acid base reaction HX + B X + HB + IONIC EQUILIBRIUM_ADVANCED #

4 Forward reaction Here HX, being a proton donor, is an acid B, being a proton acceptor, is a base. Backward reaction Here HB +, being a proton donor, is an acid X, being a proton acceptor, is a base. Acid Base Conjugate Conjugate Acid Base HCl + H O H 3 O + + Cl H + NH 3 NH [Fe(H O) 6 ] 3+ +H O H 3 O + + [Fe(H O) 5 (OH)] + Conjugate acid - base pair differ by only one proton Strong acid will have weak conjugate base and vise versa Reaction will always proceed from strong acid to weak acid or from strong base to weak base. eg. Acid Conjugate base Base Conjugate acid HCl Cl NH 3 NH + 4 H H H O H 3 O + H SO 4 RNH RNH + 3 H O OH Amphoteric (amphiprotic) : substances which can act as acid as well as base are known as amphoteric HCl + H O base H 3 O + + Cl NH 3 + H O acid NH OH LEWIS CONCEPT (ELECTRONIC CONCEPT) : An acid is a molecule/ion which can accept an electron pair with the formation of a coordinate bond. Acid e pair acceptor e.g. Electron deficient molecules : BF 3, AlCl 3 Cations : H +, Fe +, Na + Molecules with vacant orbitals : SF 4, PF 3 A base is any molecule/ion which has a lone pair of electrons which can be donated. Base (electron pair donor) e.g. Molecules with lone pairs (ligands) : NH 3, PH 3, H O, CH 3 OH PROPERTIES OF WATER : Amphoteric (amphiprotic) Acid/base nature: Water acts as an acid as well as base according to Arhenius and Bronsted-Lowry theory but according to Lewis concept it can be generally taken as base. In pure water [H + ] [OH ] so it is Neutral. Molar concentration / Molarity of water : Molarity No. of moles/litre 000gm / litre 8gm / mole gm/cc) Ionic product of water : According to Arrhenius concept mole /litre M (density H O H + + OH so, ionic product of water, K w [H + ][OH ] 0 4 at 5 (exp.) IONIC EQUILIBRIUM_ADVANCED # 3

5 dissociation of water, is endothermic, so on increasing temperature K eq. increases K w increases with increase in temperature. Now ph log[h + ] 7 and poh log[oh ] 7 for water at 5 (experimental) ph 7 poh neutral ph < 7 or poh > 7 acidic at 5 C ph > 7 or poh < 7 Basic Ionic product of water is always a constant whatever has been dissolved in water since its an equilibrium constant so will be dependent only on temperature. Degree of dissociation of water : H O no. of molesdissociated H + + OH x0 or.8x0 % total no.of molesinitiallytaken Absolute dissociation constant of water : H O H + +OH [H ][OH ] K a K b.80 [HO] So, pk a of H O pk b of H O log ( ) 6 log ph CALCULATIONS OF DIFFERENT TYPES OF SOLUTIONS : Strong acid Solution : (i) (ii) If concentration is greater than 0 6 M In this case H + ions coming from water can be neglected, so [H + ] normality of strong acid solution. If concentration is less than 0 6 M In this case H + ions coming from water cannot be neglected, So [H + ] normality of strong acid + H + ions coming from water in presence of this strong acid Strong base Solution : Calculate the [OH ] which will be equal to normality of the strong base solution and then use K W [H + ] [OH ] 0 4, to calculate [H + ]. ph of mixture of two strong acids : If V volume of a strong acid solution of normality N is mixed with V volume of another strong acid solution of normality N, then m. equi. of H + ions from -solution N V m. equi. of H + ions from -solution N V If final normality is N and final volume is V, then NV N V + N V [dissociation equilibrium of none of these acids will be disturbed as both are strong acid] N [H + V ] N V NV V ph of mixture of two strong bases : similar to above calculation [OH NV ] N V NV V & [H + ] 0 4 [OH] IONIC EQUILIBRIUM_ADVANCED # 4

6 ph of mixture of a strong acid and a strong base : Acid Base neutralisation reaction will take place. The solution will be acidic or basic depending on which component has been taken in excess. If V volume of a strong acid solution of normality N is mixed with V volume of a strong base solution of normality N, then Number of m. eq. H + ions from -solution N V Number of m. eq. OH ions from -solution N V ph of a weak acid(monoprotic) Solution : Weak acid does not dissociated 00% therefore we have to calculate the percentage dissociation using K a dissociation constant of the acid. We have to use Ostwald s Dilution law (as we have been derived earlier) HA H + + OH t 0 C 0 0 t t eq C( ) C C K a [H ] [OH ] [HA] C If << K a C C K a ( is valid if < 0. or 0%) [H + ] C C C K a C K a So ph pk a log C on increasing dilution C and [H + ] ph ph of a mixture of weak acid(monoprotic) and a strong acid Solution : Weak acid and Strong acid both will contribute H + ion. For the first approximation we can neglect the H + ions coming from the weak acid solution and calculate the ph of the solution from the concentration of the strong acid only. To calculate exact ph, we have to take the effect of presence of strong acid on the dissociation equilibrium of the weak acid. If [SA] C and [WA] C, then [H + ] from SA C the weak acid will dissociate as follows. HA H + + A C 0 0 C ( C C C K a (C C)C C ( ) ( ) (The weak acids dissociation will be further suppressed because of presence of strong acid, common ion effect) K a (C C ) Total H + ion concentration C + C If the total [H + ] from the acid is greater than 0 6 M, then contribution from the water can be neglected at 5ºC temp., if not then we have to take [H + ] from the water also. IONIC EQUILIBRIUM_ADVANCED # 5

7 then ph of a mixture of two weak acid (both monoprotic) solutions : Both acids will dissociate partially. Let the acid are HA & HA and their concentrations in the mixture are C & C respectively, HA H + + A HA H + + A t 0 C 0 0 C 0 0 At eq. C ( ) C +C C C ( ) C +C C K a C(C C ) C ( ) K a (Since, both are small in comparision to unity) K a (C C ) K a (c c ) (C C)C C ( ) Ka K a [H + ] C + C C K C K a a C K a + C K C a K a C K a [H + ] CK a CKa If the dissociation constant of one of the acid is very much greater than that of the second acid then contribution from the second acid can be neglected. So, [H + ] C + C C ph of a Solution of a polyprotic weak acid : Diprotic acid is the one, which is capable of giving protons per molecule in water. Let us take a weak diprotic acid (H A) in water whose concentration is C molar. In an aqueous solution, following equilbria exist. degree of ionization of H A in presence of HA K a first ionisation constant of H A. degree of ionisation of HA in presence of H A. K a second ionisation constant of H A. I step II step H A HA + H + HA A + H + c( ) c ( ) (c + c ) c ( ) c (c + c ) K a [H ][HA [H A] ] K a [H ][A ] [HA ] K a (c c )[c( )] c( ) K a (c c )(cc ) c ( ) [c( )][ ( )]...(i) [c( )]...(ii) Knowing the values of K a, K a and c, the values of and can be calculated using equations (i) and (ii). After getting the values of and [H 3 O + ] can be calculated as. [H 3 O + ] T c + c Finally, for calculating ph If the total [H 3 O + ] < 0 6 M, the contribution of H 3 O + from water should be added If the total [H 3 O + ] > 0 6 M, then [H 3 O + ] contribution from water can be ignored. Using this [H 3 O + ], ph of the solution can be calculated. IONIC EQUILIBRIUM_ADVANCED # 6

8 Approximation For diprotic acids, K a < < K a and would be even smaller than. and + Thus, equation (i) can be reduced to K a C This is an expression similar to the expression for a weak monoprotic acid. Hence, for a diprotic acid (or a polyprotic acid) the [H 3 O + ] can be calculated from its first equilibrium constant expression alone provided K a << K a. Neutralisation : A reaction between acid and base to form salt and water molecule is known as neutralisation. In this type of reaction acid gives H + ion and base gives OH ion. Hydrolysis It is defined as a process involving the reaction of water on a salt to form mixture of acid and base. (a) (b) (c) It is the just reverse process of neutralization Salt + water Acid + Base In this reaction the solution is always neutral when both acid and base are strong. If acid is stronger than base, the solution is acidic and if base is stronger than acid, the solution is basic. (d) Depending upon the nature of an acid or a base, there can be four types of salt - Strong Weak (i) Salt of strong acid and strong base. (ii) Salt of strong acid and weak base. (iii) Salt of weak acid and weak base. (iv) Salt of weak acid and strong base. Strong Weak acids acids bases bases HCl CH 3 COOH NaOH NH 4 OH H HCN KOH LiOH HNO 3 H RbOH Ca(OH) HClO 4 H 3 CsOH Be(OH) HI H 3 PO 3 Ba(OH) Zn(OH) H SO 3 HOCl Al(OH) 3 COOH COOH RNH Fe(OH) NH 3 3 ANIONIC HYDROLYSIS Anions can function as a base on reaction with water and hydrolyse as follows : A (aq) + H O (l) HA (aq) + OH (aq) The extent of hydrolysis of a given anion depends on its basic strength IONIC EQUILIBRIUM_ADVANCED # 7

9 CATIONIC HYDROLYSIS Cations can function as acid on reaction with water and hydrolyze as follows. B + (aq) + H O(l) BOH(aq) H 3 O + (aq) The extent of hydrolysis of a given cation depends on its acidic strength. (i) Hydrolysis of Salt of Strong acid and Strong base : Salt of strong acid and strong base does not hydrolysed. (ii) Salt of strong acid and weak base B + + H O BOH + H + K h [ BOH] [ H ] K h [ B ] K K W b Kh h C ph 7 pk b log C Here, on the study of above equation, we can say that the ph of the strong acid weak base is less than 7. (iii) Salt of weak acid and strong base A + H O OH + HA K h [ HA] [ OH ] [ A ] K h K K W a h Kh C ph 7 + pk a + log C (iv) Salt of weak acid and weak base B + + A + H O HA + BOH K h [ HA] [ BOH] [ B ] [ A ] K h KW K K a b h KW K K a b ph 7 + pk a pk b IONIC EQUILIBRIUM_ADVANCED # 8

10 Hydrolysis of Amphiprotic Anion. (Cation is not Hydrolysed) NaH, NaHS, etc., can undergo ionisation to from H + ion and can undergo hydrolysis to form OH (Na + ion is not hydrolysed) (a) (i) H + H O CO + 3 (ii) H + H O H + ph(hco pk 3 ) a pka (b) Similarly for H and H amphiprotic anions. ph(h ) pk a pka and ph(hpo pk 4 ) a pka3 Buffer Solution (if the acids and bases are mixed in different amounts (equivalents)) (i) In certain applications of chemistry and biochemistry we require solutions of constant ph. Such solution are called buffer solution. (ii) A solution whose ph is not altered to any great extent by the addition of small quantities of either an acid (H + ions) or a base (OH ions) is called buffer solution. (iii) Buffer solutions are also called solutions of reverse acidity or alkalinity. (iv) Following are the characteristics of buffer solutions (a) It must have constant ph. (b) Its ph should not be changed on long standing (c) Its ph should not be changed on dilution. (d) It ph should not be changed to any great extent on addition of small quantity of acid or base. (v) Buffer solutions can be classified as follows. (A) Simple buffer (B) Mixed buffer Acidic buffer These are the mixture of a weak acid and its salt with strong base. e.g. (a) CH 3 COOH + CH 3 COONa (b) Boric acid (H 3 BO 3 ) + Borax (Na B 4 O 7 ) ph pk a + log [ Salt ] [ Acid ] IONIC EQUILIBRIUM_ADVANCED # 9

11 Basic Buffer These are the mixture of a weak base and its salt with strong acid. e.g. (a) (b) NH 4 OH + NH 4 Cl Glycine (NH CH COOH) + Glycine hydrochloride (Cl + NH 3 CH COOH) or poh pk b + log [ Salt ] [Base] Buffer Capacity (i) The property of a buffer solution to resist alteration in its ph value is known as buffer capacity. (ii) Buffer capacity is number moles of acid or base added in one litre of solution as to change the ph by unity, i.e. Buffer capacity () b or ( ph) Number of moles acid or base added to l sol. Change inph where b is number of moles of acid or base added and (ph) is change in ph. INDICATOR : ph pk n + log [Ionised form] [Unionised form] SOLUBILITY(S) AND SOLUBILITY PRODUCT (K SP ) At a constant temperature, the mass of a solute or electrolyte dissolved in the 00 gm of solvent in its saturated solution is called as solubility. Or number of gm mole of a solute dissolved in one litre of water at constant temperature is called as solubility of that solute. Solubility of a solute in moles / litre Solubility of solute in gm / litre molecular weight of the solute Relationship between Solubility and Solubility Product : The equilibrium for a saturated solution of a salt A x B y may be expressed as, A x B y xa y+ + yb x Thus, solubility product K SP [A y+ ] x [B x ] y Let the solubility of the salt A x B y in water at a particular temperature be s moles per litre then So, A x B y xa y+ + yb x K SP [xs] x [ys] y K SP x x. y y (s) x + y xs ys (a) : types salts or AB type of salts : eg. AgCl, AgI, Ba, Pb, etc. AB A + + B let the solubility of AB is s moles per litre. So, K SP [A + ] [B ] s s s s K SP IONIC EQUILIBRIUM_ADVANCED # 0

12 (b) : or : type of salts or AB or A B type of salts : eg. Ag CrO 4, PbI, Ag, CaF, CaCl etc. (i) AB A + + B s s let the solubility of AB is s moles per litre So, K SP [A + ][B ] s (s) 4s 3 s 3 K SP 4 (ii) A B A + + B let s the solubility of A B So, A B A + + B s s K SP [A + ] [B ] (s) (s) 4s 3 s 3 K SP 4 (c) : 3 type of salts or salts of AB 3 or A 3 B type of salt - AB 3 Valency of A 3 Valency of B eg. FeCl 3, AlCl 3, PCl 3, Al(OH) 3, Fe(OH) 3 etc. A 3 B 3 Valency of A Valency of B eg. Na 3 BO 3, Na 3, H 3 etc. (i) AB 3 A B let the solubility of A 3 B is s mole / litre. AB 3 A B s 3s K SP [A 3+ ] [B ] 3 s (3s) 3 7s 4 K s 4 SP 7 (ii) A 3 B 3A + + B 3 let the solubility of A 3 B is s moles/litre. A 3 B 3A + + B 3 3s s K SP [A + ] 3 [B 3 ] (3s) 3 s 7s 4 K s 4 SP 7 (d) : 3 or A B 3 type of salts : eg. Al ( ) 3 A B A B let the solubility of salt A B 3 is s - So, A B 3 A B K SP [A +3 ] [B ] 3 (s) (3s) 3 4s 7 s 3 K SP 08 s 5 K s 5 SP 08 s 3s IONIC EQUILIBRIUM_ADVANCED #

13 PART - I : OBJECTIVE QUESTIONS * Marked Questions are having more than one correct option. Section (A) : Basics and acid - base concept A-. A-.* The following equilibrium is established when hydrogen chloride is dissolved in acetic acid. HCl (aq) + CH 3 COOH (aq) Cl (aq) + CH 3 COOH + (aq). The set that characterises the conjugate acid-base pairs is : (A) (HCl, CH 3 COOH) and (CH 3 COOH +, Cl ) (B) (HCl, CH 3 COOH + ) and (CH 3 COOH, Cl ) (C) (CH COOH +, HCl) and (Cl, CH 3 COOH) (D) (HCl, Cl ) and (CH 3 COOH +, CH 3 COOH). Identify acid and base in the following reaction according to Bronsted - Lowry concept. (a) [Cu(H O) 3 (OH)] + (aq.) + [Al(H O) 6 ] 3+ (aq.) [Cu(H O) 4 ] + (aq.) + [Al(H O) 5 OH] + (aq.) (b) [Fe(H O) 5 (OH)] + (aq.) + [Al(H O) 6 ] 3+ (aq.) [Fe(H O) 6 ] 3+ (aq.) + [Al(H O) 5 (OH)] + (aq.) (c) O (aq.) + H O (aq.) OH (aq.) (d) CH 3 OH (aq.) + H (aq.) CH 3 O (aq.) + H (g) Acid Base (A) [Al(H O) 6 ] 3+ [Cu(H O) 3 (OH)] + (B) [Al(H O) 6 ] 3+ [Fe(H O) 5 (OH)] + (C) H O O (D) CH 3 OH H A-3. 3 In the following reaction HC O 4 (aq) + (aq) H (aq) + C O 4 (aq), which are the two Bronsted bases? 3 (A) HC O 4 and (B) H and C O 4 (C) HC O 4 and H 3 (D) and C O 4 A-4. If the acid-base reaction HA(aq) + B (aq) HB(aq) + A (aq) has a K eq. 0 4, which of the following statements are true? (i) HB is stronger acid than HA. (ii) HA is stronger acid than HB. (iii) HA and HB have the same acidity. (iv) B is stronger base than A. (v) A is stronger base than B. (vi) B and HB are conjugate acid-base pair. (vii) the acid and base strengths connot be compared. (A) i, iii, v (B) i, v, vi (C) ii, iv, vi (D) iv, v, vi Section (B) : Ostwald dilution concept, property of water, ph definition B-. Which of the following expression is not true? (A) [H + ] [OH ] K W for a neutral solution at all temperatures. (B) [H + ] > K W & [OH ] < K W for an acidic solution (C) [H + ] < K W & [OH ] > K W for an alkaline solution (D) [H + ] [OH ] 0 7 M for a neutral solution at all temperatures. B-.* 0. mole of which of the reagents listed below [(i) to (vi)] could be added to one litre of water to make 0.0 M + solutions of each of the following ions (a) NH 4 ; (b) CH 3 COO ; (c) Cl separatly, respectively? (i) NH 3 ; (ii) NH 4 Cl ; (iii) CH 3 COOH ; (iv) CH 3 COONa ; (v) HCl ; (vi) NaCl (A) ii, iv, ii (B) ii, iv, v (C) ii, iv, vi (D) ii, iv, iii B-3. Which of the following relations is correct? (A) Gº RT ln K eq (B) [H 3 O + ] 0 ph (C) log Kw Hº Kw.303R T T (D) [OH ] 0 7, for pure water at all temperatures. IONIC EQUILIBRIUM_ADVANCED #

14 B-4. poh of H O is 7.0 at 98 K. If water is heated at 350 K, which of the following statement should be true? (A) poh will decrease. (B) poh will increase. (C) poh will remain 7.0. (D) concentration of H + ions will increase but that of OH will decrease. B-5. Percentage ionisation of water at certain temperature is %, Calculate K w and ph of water. (A) 0 4, ph 6.7 (B) 4 0 4, ph 6.7 (C) 0 4, ph 7 (D) 0 4, ph 7 B-6. Which of the following has the highest degree of ionisation? (A) M NH 3 (B) 0.00 M NH 3 (C) 0. M NH 3 (D) M NH 3. B-7. A 50 ml solution of strong acid of ph is mixed with a 50 ml solution of strong acid of ph. The ph of the mixture will be nearly : (log ) (A) 0.74 (B).6 (C).76 (D).5 B-8.* K w of H O at 373 K is 0. Identify which of the following is/are correct? (A) pk w of H O is (B) ph of H O is 6 (C) H O is neutral (D) H O is acidic. Section (C) : SA,. SB and their mixture C-. A litre solution of ph 4 (solution of a strong acid) is added to the 7/3 litre of water. What is the ph of resulting solution? (log ) (A) 4 (B) 4.48 (C) 4.5 (D) 5 C-. Which of the following solution will have a ph exactly equal to 8? (A) 0 8 M HCl solution at 5ºC (B) 0 8 M H + solution at 5ºC (C) 0 6 M Ba(OH) solution at 5ºC (D) 0 5 M NaOH solution at 5ºC C-3. The [OH ] in 00.0 ml of 0.06 M-HCl (aq) is : (A) 5 0 M (B) M (C) M (D) M. C-4. How many moles of NaOH must be removed from one litre of aqueous solution to change its ph from to? (A) (B) 0.0 (C) 0.0 (D) 0. C-5. Which of the following solution will have ph close to.0? (A) 00 ml of M/0 HCl + 00 ml of M/0 NaOH (B) 55 ml of M/0 HCl + 45 ml of M/0 NaOH (C) 0 ml of M/0 HCl + 90 ml of M/0 NaOH (D) 75 ml of M/5 HCl + 5 ml of M/5 NaOH. C-6. 0.mol HCl is dissolved in distilled water of volume V then at lim V (ph) is equal to : solution (A) zero (B) (C) 7 (D) 4 C-7. The ph of a solution obtained by mixing 50 ml of 0.4 N HCl and 50 ml of 0. N NaOH is : (A) 3 (B) (C).0 (D).0 Section (D) : ph of weak acid and weak base, polyprotic acid and base D-. Which statement/relationship is correct? (A) ph of 0. M HNO 3, 0.M HCl, 0.M H are not equal. (B) ph log [H ] (C) At 5 C the ph of pure water is 7. (D) The value of pk w at 5 C is 7. D-. K a for a monobasic acid whose 0.0 M solution has ph of 4.5. (log ) (A) (B) (C) (D) 0 IONIC EQUILIBRIUM_ADVANCED # 3

15 D-3. K b for a monoacidic base whose 0.0 M solution has a ph of (A) (B) (C) (D) D-4. One litre of solution contains 0 5 moles of H + ions at 5 C. Percentage ionisation of water in solution is : (A) % (B) % (C) % (D).8 0 %. D-5. Calculate the ph of 500 ml of M hydrazoic acid (HN 3 ). (K a.5 0 5, log 5 0.7) (A).7 (B).3 (C).4 (D).7 D-6. For ortho-phosphoric acid, H 3 (aq) + H O (aq) H 3 O + (aq) + H PO (aq) ; 4 K a H (aq) + H O (aq) H 3 O + (aq) + HPO (aq) ; K 4 a HPO (aq) + H 4 O (aq) H 3 O + 3 (aq) + PO (aq) ; K 4 a3 The correct order of K a values is : (A) K a > K a < K a (B) K 3 a < K a < K a (C) K 3 a > K a > K a (D) K 3 a < K a > K a 3 D-7. What is the ph of 0.0 M H S solution? K a 9 0 8, K a (A) 4.5 (B) 3.5 (C) 4.48 (D) 3.48 Section (E) : Mixtures of acids and bases E-. Consider an aqueous solution, 0. M each in HOCN, HCOOH, (COOH) and H 3, for HOCN, we can write K a (HOCN) [H ][OCN ]. [H + ] in this expression refers to : [HOCN] (A) H + ions released by HOCN. (B) Sum of H + ions released by all monoprotic acids. (C) Sum of H + ions released only the first dissociation of all the acids. (D) Overall H + ion concentration in the solution. E-. What concentration of Ac ions will reduce H 3 O + ion to 0 4 M in 0.40 M solution of HAc? K a (HAc).8 0 5? (A) 0.08 M (B) M (C) 0008 M (D) M E-3. E-4. The dissociation constant of acetic acid at a given temperature is The degree of dissociation of 0.0 M acetic acid in the presence of 0.0 M HCl is equal to : (A) 0.4 (B) 0.3 (C) (D) What are [H + ], [A ] and [B ] in a solution that contains 0.03 M HA and 0. M HB? K a for HA and HB are and respectively. (A) [H + ] [A ] M, [B ] M (B) [H + ] [A ] M, [B ] M (C) [H + ] [A ] 0 3 M, [B ] M (D) [H + ] [A ] M, [B ] M Section (F) : Salt hydrolysis F-. Which of the following salts undergoes anionic hydrolysis? (A) Cu (B) NH 4 Cl (C) AlCl 3 (D) K. F-. An aqueous solution of aluminium sulphate would show : (A) An acidic reaction. (B) A neutral reaction. (C) A basic reaction. (D) Both acidic and basic reactions. F-3. Which of the following is an acidic salt? (A) Na (B) Ca(OH)Cl (C) Pb(OH)Cl (D) Na H IONIC EQUILIBRIUM_ADVANCED # 4

16 F-4. Expression pk h pk w pk a pk b is not applicable to : (A) Ammonium acetate (B) Ammonium cyanide (C) Aniline acetate (D) Ammonium chloride F-5. What is the ph of an aqueous solution of ammonium acetate? (K a K b ) (A) > 7 (B) 7.0 (C) < 7.0 (D) Zero F-6. If pk b > pk a then the solution of the salt of weak acid and weak base will be : (A) Neutral (B) Acidic (C) Basic (D) Amphoteric F-7. poh pk a pk b is true for which pair of cation and anion? (A) C 6 H 5 NH 3 +, CH 3 COO (B) Na +, CN (C) Al +3, Cl (D) NH 4 +, NO 3 F-8. For a salt of weak acid and weak base [pk a pk b ] would be equal to : (A) ph + pk w (B) ph log 0 4 (C) ph pk w (D) None of these F-9. Which of the following compound forms an aqueous solution which is acidic when compared with water? (A) NaOH (B) K (C) BaCl (D) Al ( ) 3 F-0. The salt of which of the following four weak acids will be most hydrolysed? (A) HA ; K a 0 8 (B) HB ; K a 0 6 (C) HC ; K a (D) HD ; K a F-. Formula for degree of hydrolysis h ; h [ 0 7 (K a K b ) ½ ] is applicable to the salt : (A) NH 4 CN (B) (NH 4 ) (C) NH 4 Cl (D) NH 4 NO 3 K F-. [H + wk a ] is suitable for : C (A) NaCl, NH 4 Cl (B) CH 3 COONa, NaCN (C) CH 3 COONa, (NH 4 ) (D) CH 3 COONH 4, ( NH 4 ) F-3. The sodium salt of a certain weak monobasic organic acid is hydrolysed to an extent of 3% in its 0.M solution at 5 0 C. Given that the ionic product of water is 0 4 at this temperature, what is the dissociation constant of the acid? (A) x 0 0 (B) x 0 9 (C) 3.33 x 0 9 (D) 3.33 x 0 0 F-4. The ph of a solution obtained by mixing 00 ml of 0. M CH 3 COOH with 00 ml of 0. M NaOH would be : (pk a for CH 3 COOH 4.74) (A) 4.74 (B) 8.87 (C) 9.0 (D) 8.57 F-5. ph of 0.M Na H and 0.M NaH respectively are : (pk a for H 3 are., 7. and.0). (A) 4.7, 9.6 (B) 9.6, 4.7 (C) 4.7, 5.6 (D) 5.6, 4.7 F-6. The ph of 0. M solution of the following salts increases in the order : [JEE-999, /80] (A) NaCl < NH 4 Cl < NaCN < HCl (B) HCl < NH 4 Cl < NaCl < NaCN (C) NaCN < NH 4 Cl < NaCl < HCl (D) HCl < NaCl < NaCN < NH 4 Cl IONIC EQUILIBRIUM_ADVANCED # 5

17 Section (G) : Buffer Solution G-. The ph of buffer of NH 4 OH + NH 4 Cl - type is given by : (A) ph pk b (B) ph /pk b / log [salt ] / [base] (C) ph 4 pk b log [salt] / [base] (D) ph poh pk b + [salt] / [base] G-. A basic buffer solution can be prepared by mixing the solution of : (A) ammonium chloride and ammonium acetate (B) ammonium acetate and acetic acid (C) ammonium chloride and ammonium hydroxide (D) ammonium cyanide and ammonium hydroxide G-3. In the neutralization process of H 3 and NaOH, the number of buffers formed will be : (A) 3 (B) (C) (D) 4 G-4. Addition of sodium acetate solution to acetic acid causes the following change : (A) ph increases. (B) ph decreases. (C) ph remains unchanged. (D) ph becomes 7. G-5. H + ion concentration of water does not change by adding : (A) CH 3 COONa (B) NaNO 3 (C) NaCN (D) Na G-6. G-7. G-8. H + NaH found in blood helps in maintaining ph of the blood close to 7.4. An excess of acid entering the blood stream is removed by : (A) HC O 3 (B) H (C) H + ion (D) ion A solution is 0. M CH 3 COOH and 0. M CH 3 COONa. Which of the following solution will change its ph significantly? (A) Addition of water (B) Addition of small amount of CH 3 COONa with out change in volume (C) Addition of small amount of CH 3 COOH with out change in volume (D) None will change the ph significantly. K a for HCN is at 5 C. For maintaining a constant ph of 9, the volume of 5 M KCN solution required to be added to 0 ml of M HCN solution is : (log 0.3) (A) 4 ml (B) 8 ml (C) ml (D) 0 ml G-9. Which of the following solutions would have same ph? (A) 00 ml of 0. M HCl + 00 ml of 0.4 M NH 3 (B) 50 ml of 0. M HCl + 50 ml of 0. M NH 3 (C) 00 ml of 0.3 M HCl + 00 ml of 0.6 M NH 3 (D) All will have same ph. G-0.* Which of the following is/are correct regarding buffer solution? (A) It contains weak acid and its conjugate base. (B) It contains weak base and its conjugate acid. (C) It shows large change in ph on adding small amount of acid or base. (D) All of the above. G-.* A buffer solution can be prepared from a mixture of : [JEE-999, 3/80] (A) sodium acetate and acetic acid in water (B) sodium acetate and hydrochloric acid in water (C) ammonia and ammonium chloride in water (D) ammonia and soldium hydroxide in water G-. G ml of 0.0 M solution of the acid HA (K a.0 x 0 5 ) & 50 ml of an NaA solution are given. What should be the concentration of the NaA solution to make a buffer solution with ph 4.00? (A) 0.0 M (B) 0.0 M (C) 0. M (D) 0. M Calculate the ph of a solution resulting from the addition of.5 ml of 0. M HCl to 50 ml of a solution containing 0.5 M CH 3 COOH & 0. M CH 3 COONa. (pk a 4.74) (A) 4.6 (B) 3.74 (C) 4.74 (D) 5.74 IONIC EQUILIBRIUM_ADVANCED # 6

18 Section (H) : Acid-base Titration H-.* Which one is the correct graph (figure) for the corresponding acid-base titration? ph ph (A) (B) volume of strong base added to a monobasic strong acid volume of strong acid added to a monoacidic weak base ph ph (C) (D) volume of strong base added to a weak dibasic acid volume of strong acid added to a weak diacidic base H-. H-3.* 00 ml of 0.0 M benzoic acid (pka 4.) is titrated using 0.0 M NaOH. ph after 50 ml and 00 ml of NaOH have been added are (A) 3.50, 7 (B) 4., 7 (C) 4., 8. (D) 4., 8.5 A weak acid (or base) is titrated against a strong base (or acid), volume v of strong base (or acid) is plotted against ph of the solution (as shown in figure). The weak electrolyte (i.e. acid or base) could be : (A) Na (B) Na C O 4 (C) H C O 4 (D) CH (COOH) H-4. H-5. If the solubility of lithium sodium hexafluorido aluminate, Li 3 Na 3 (AlF 6 ) is s mol lt, its solubility product is equal to : (A) 79 s 8 (B) s 8 (C) 3900 s 8 (D) 96 s 8 The solubility product Mg(OH) in water at 5 º C is (mol/lt) 3 while that of Al(OH) 3 is (mol/lt) 4. If s and s are the solubilities of Mg(OH) and Al(OH) 3 in water in mol/lt at 5 0 C, what is the ratio, s /s? (A) 0 5 (B) 0 4 (C) (D) H-6. The solubility of CaF (K sp ) in 0. M solution of NaF would be : (A) M (B) M (C) M (D) M. H-7. In a saturated solution of Ag, silver ion concentration is 0 4 M. Its solubility product is : (A) 4 0 (B) 3. 0 (C) 8 0 (D) 0 H-8. The solubility of Ag in water at 5 0 C is 0 4 mole/litre. What is its solubility in 0.0 M Na solution? Assume no hydrolysis of ion. (A) mole/litre (B) mole/litre (C) 0 5 mole /litre (D) 0 5 mole/litre H-9. Let the solubilities of AgCl in pure water, 0.0 M CaCl, 0.0 M NaCl & 0.05 M AgNO 3 be s, s, s 3 & s 4 respectively what is the correct order of these quantities. Neglect any complexation. (A) s > s > s 3 > s 4 (B) s > s s 3 > s 4 (C) s > s 3 > s > s 4 (D) s 4 > s > s 3 > s IONIC EQUILIBRIUM_ADVANCED # 7

19 Section (I) : Solubility in buffer, Complex formation, Selective precipitation I-. I-. The solubility product of AgCl is Precipitation of AgCl will occur only when equal volumes of solutions of (A) 0 4 M Ag + and 0 4 M Cl are mixed. (B) 0 7 M Ag + and 0 7 M Cl are mixed. (C) 0 5 M Ag + and 0 5 M Cl are mixed. (D) 0 5 M Ag + and 0 5 M Cl are mixed. The solubility product of BaCrO 4 is M. The maximum concentration of Ba(NO 3 ) possible without precipitation in a M K CrO 4 solution is : (A) M (B). 0 0 M (C) M (D) M. I-3. What is the solubility of Al(OH) 3, (K sp 0 33 ) in a buffer solution ph 4? (A) 0 3 M (B) 0 6 M (C) 0 4 M (D) 0 0 M. I-4. The solubility of Fe(OH) 3 would be maximum in : (A) 0. M NaOH (B) 0. M HCl (C) 0. M KOH (D) 0. M H. I-5. Which of the following statements is correct for a solution saturated with AgCl and AgBr if their solubilities in moles per litre in separate solutions are x and y respectively? (A) [Ag + ] x + y (B) [Ag + ] [Br ] + [Cl ] (C) [Br ] y (D) [Cl ] > x. I-6. If s is the molar solubility of Ag, then : (A) 3 [Ag + ] s (B) [Ag + ] s (C) [Ag + ] s (D) [ ] s I-7. Which of the following would increase the solubility of Pb (OH)? (A) Add hydrochloric acid (B) Add a solution of Pb(NO 3 ) (C) Add a solution of NaOH (D) None of the above the solubility of a compound is constant at constant temperature I-8. The aqueous solution of which of the following sulphides would contain maximum concentration of S ions? (A) MnS (K sp. 0 ) (B) ZnS (K sp. 0 3 ) (C) PbS (K sp ) (D) CuS (K sp ) I-9. Which of the following salts has maximum solubility? (A) HgS, K sp (B) Pb, K sp (C) ZnS, K sp (D) AgCl, K sp I-0. The necessary condition for saturated solution is : (A) Product of ionic concentrations Solubility product (B) Product of ionic concentrations < solubility product (C) Product of ionic concentrations > solubility product (D) None of the above I-. At 30ºC, the solubility of Ag (K sp 8 0 ) will be maximum in : (A) 0.05 M Na (B) 0.05 M AgNO 3 (C) Pure water (D) 0.05 NH 3 I-. Which of the following expressions shows the saturated solution of Pb? (A) K sp (Pb ) [Pb + ] [ ] (B) K sp (Pb ) > [Pb + ] [ ] (C) K sp (Pb ) [Pb + ] [ ] (D) K sp (Pb ) < [Pb + ] [ ] I-3. The correct relation between K sp and solubility for the salt KAl( ) is : (A) 4s 3 (B) 4s 4 (C) 7s 4 (D) none I-4. The solubility of a sparingly soluble salt A x B y in water at 5ºC M. The solubility product is. 0. The possibilities are : (A) x, y (B) x, y (C) x, y 3 (D) x 3, y IONIC EQUILIBRIUM_ADVANCED # 8

20 PART - II : MISCELLANEOUS QUESTIONS COMPREHENSIONS TYPE Comprehension # Read the following passage carefully and answer the questions. Pure water is a weak electrolyte and neutral in nature, i.e. H + ion concentration is exactly equal to OH ion concentration [H + ] [OH ]. When this condition is disturbed by decreasing the concentration of either of the two ions, the neutral nature changes into acidic or basic. When [H + ] > [OH ], the water becomes acidic and when [H + ] < [OH ], the water acquires basic nature. This is exactly the change which occurs during the phenomenon known as salt hydrolysis. The ph of salt solution can be calculated using the following relations: ph [pkw + pk a + log C] for salt of weak acid and strong base. ph [pkw pk b log C] for salt of weak base and strong acid. ph [pkw + pk a pk b ] for salt of weak acid and weak base. where C represents the concentration of salt. When a weak acid or a weak base is not completely neutralized by strong base or strong acid respectively, then formation of buffer takes place. The ph of buffer solution can be calculated using the following relation : ph pk a + log [Salt] ; poh pk [Acid] b + log [Salt] [Base] Answer the following questions using the following data : pk a , pk b , pk w 4. When 50 ml of 0. M NH 4 OH is added to 50 ml of 0.05 M HCl solution, the ph is : (A).60 (B).3979 (C) (D) ml 0. M NaOH is added to 50 ml of 0. M CH 3 COOH solution, the ph will be : (A) (B) (C) 8.78 (D) When 50 ml of 0. M NaOH is added to 50 ml of 0.05 M CH 3 COOH solution. The ph of the solution is : (A).60 (B).3979 (C) (D) 8.78 COMPREHENSION # Strontium fluoride (SrF ) is a sparingly soluble salt. Let s be its solubility (in mol/lt.) in pure water at 5 C, assuming no hydrolysis of F ions. Also, let s be its solubility (in mol/lt.) in 0. M NaF solution at 5 C, assuming no hydrolysis of F ions and no complex formation. However, it is known that s : s 0 6 : 56. Now, answer the following questions. 4. The K sp value of SrF at 5 C is : (A) (B) (C) (D) The mass of NaF to be added to 00 ml solution of 0.00 M Sr + ions to reduce its concentration to 0 4 M is : [Assume no hydrolysis of F ions] (A) 0.4 g (B) g (C) 0.0 g (D) g 6. The solubility of SrF (in mol/l) in a buffer solution of ph 5 at 5 C is : [Given : K a for HF ] (A) (B) (C) (D) IONIC EQUILIBRIUM_ADVANCED # 9

21 MATCH THE COLUMN 7. (Use log.8 0.6, K a of formic acid.8 0 4, K a of acetic acid.8 0 5, K b of ammonia.8 0 5, K a of H S 0 7 and K a of H S 0 4, for the following matchings) Match the entries of column II for which the equality or inequality given in the column I are satisfied. Column I (A) 0 5 M HCl solution > 0. M H S solution Column II (p) water ( degree of dissociation of water) (B) CH 3 COOH solution at ph equal to 4.74 (q) [OH ] NH 4 OH solution at ph equal to 9.6 (C) 0. M CH 3 COOH solution.0 M HCOOH solution (D) 0. M of a weak acid HA (K a 0 5 ) solution < 0.0 M of a weak acid HA (K a 0 6 ) solution (r) (degree of dissociation of electrolytes) (s) ph 8. Column I Column II (A) AgBr (p) Solubility in water is more than expectation. (B) AgCN (q) Solubility in acidic solution is more than that in pure water. (C) Fe(OH) 3 (r) Solubility in strongly basic solution is more than that in pure water. (D) Zn(OH) (s) Solubility decreases in presence of common anion. ASSERTION / REASONING DIRECTIONS : Each question has 5 choices (A), (B), (C), (D) and (E) out of which ONLY ONE is correct. (A) Statement- is True, Statement- is True; Statement- is a correct explanation for Statement-. (B) Statement- is True, Statement- is True; Statement- is NOT a correct explanation for Statement-. (C) Statement- is True, Statement- is False. (D) Statement- is False, Statement- is True. (E) Statement- and Statement- both are False. 9. Statement- : The H 3 O + has additional water molecules closely associated with it. Statement- : In solid state the species H 5 O + and H 9 O 4 + have been found to exist. 0. Statement- : The proton transfer reaction between NH 3 and H O proceeds only to a slight extent. Statement- : Proton transfer reaction is virtually complete in the case of HCl in dilute solution.. Statement- : Acids that have more than one proton that can be donated to base are called polyprotic acids. Statement- : For all diprotic acids, the equilibrium constant K a smaller than the equilibrium constant, K a, for the first stage of ionisation.. Statement- : 0.0 M solution of NaCN is more basic than 0.0 M solution of NaF. Statement- : K a of HCN is very much less than that of HF., for the second stage of ionisation is 3. Statement- : A substance that can either act as an acid as well as a base is called ampholyte. Statement- : Bisulphide ion (HS ) and biscarbonate ion (H ) are ampholytes. IONIC EQUILIBRIUM_ADVANCED # 0

22 4. Statement- : Addition of HCl(aq) to HCOOH(aq), decrease the ionization of HCOOH(aq) Statement- : Due to common ion effect of H +, ionization of HCOOH decreased. 5. Statement- : ph of 0 7 M HCl is less than 7 at 5ºC. Statement- : At very low concentration of HCl, contribution of H + from water is considerable. 6. Statement- : In a titration of weak monoprotic acid with strong base, the ph at the half equivalent point is pk a. Statement- : At half equivalence point, it will form acidic buffer at it's maximum capacity where [acid] [salt]. 7. Statement- : Solubility of AgCl in NH 3 (aq) is greater than in pure water. Statement- : When AgCl dissolve in NH 3 (aq), complex ion [Ag(NH 3 ) + ] formation takes place and solubility equilibrium of AgCl shifted in forward direction. 8. Statement- : In the titration of Na with HCl using methyl orange indicator, the volume required at the equivalence point is twice that of the acid required using phenolphthalein indicator. Statement- : Two mole of HCl are required for the complete neutralization of one mole of Na. TRUE / FALSE 9. The ionic product of water changes if a few drops of acid or base are added to it. 0. The reaction, HCN + OH CN + H O is displaced to the right indicating that the acid strength of HCN is greater than water & the base strength of CN is greater than that of OH.. All aqueous solutions whether neutral, acidic or basic contain both H + & OH ions.. The ionic product of a saturated solution is equal to solubility product constant of its solute. 3. A salt of strong acid with a strong base does not undergo hydrolysis. 4. To a solution of 0 ml of 0. M acetic acid, a solution of 0.M NaOH is added from burette. If r is the ratio of [salt], the ph changing with respect to r when 5 ml of the alkali have been added is [acid] FILL IN THE BLANKS 5. The dissociation constant of NH 4 OH is The hydrolysis constant of NH 4 + ions at 5º C would be The colour of unionized form of phenolphthalein is whereas that of ionized form is 7. The smaller the value of K a of a weak acid, is the hydrolysis constant of its conjugate base. 8. At 90 C, pure water has [H + ] 0 6 M, then the value of K w at this temperature would be. 9. The ph of pure water with increase of temperature. 30. In a mixture of weak acid (HA) and its salt (NaA), the ratio of concentration of salt to acid is increased ten fold. The ph of the solution would by unit. 3. An indicator (Hn) will exhibit the colour of its ionized form (n ) when the solution contains more than % of the indicator in n form.. IONIC EQUILIBRIUM_ADVANCED #

23 PART - I : MIXED OBJECTIVE Single Correct Answer Type. If 50 ml of 0. M KOH is added to 40 ml of 0.5 M HCOOH. the ph of the resulting solution is : (K a.8 0 4, log 8.6) (A) 3.74 (B) 5.64 (C) 7.57 (D) 3.4. When 00 ml of 0.4 M CH 3 COOH are mixed with 00 ml of 0. M NaOH, the [H 3 O + ] in the solution is approximately : [K a (CH 3 COOH) ] (A) M (B) M (C) M (D) M. 3. What % of the carbon in the H H buffer should be in the form of H so as to have a neutral solution? (K a ) (A) 0 % (B) 40 % (C) 60 % (D) 80% 4. Buffer capacity of a buffer solution is x, the volume of M NaOH added to 00 ml of this solution if change the ph by is : (A) 0. x ml (B) 0 x ml (C) 00 x ml (D) x ml 5. What amount of HCl will be required to prepare one litre of a buffer solution of NaCN and HCN of ph 8.5 using 0.0 mole of NaCN? pk b of CN 4.6 (log 0.3) (A) 0 3 mole (B) mole (C) mole (D) mole 6. To a 00 ml of 0. M weak acid HA solution 90 ml of 0. M solution of NaOH be added. Now, what volume of 0. M NaOH be added into above solution so that ph of resulting solution be 5? [(K a (HA) 0 5 ] (A) ml (B) 0 ml (C) 0 ml (D) 5 ml ml of 0. M NaOH is added to 60 ml of 0.5 M H 3 solution (K, K and K 3 for H 3 are 0 3, 0 8 and 0 3 respectively). The ph of the mixture would be about : (log 0.3) (A) 3. (B) 5.5 (C) 4. (D) The correct relationship between the ph of isomolar solutions of Na O (ph ), Na S (ph ) Na Se(pH 3 ) and Na Te(pH 4 ) is : (A) ph > ph > ph 3 > ph 4 (B) ph < ph < ph 3 < ph 4 (C) ph < ph < ph 3 ph 4 (D) ph > ph ph 3 > ph 4 9. The ph of which salt is independent of its concentration?. (CH 3 COO)C 5 H 5 NH. NaH 3. Na H 4.NH 4 CN (A),, 3, 4 (B), 4 (C), 3 (D),, 3 0. What will be the ph at the equivalence point during the titration of a 00 ml 0. M solution of CH 3 COONa with 0. M solution of HCl? K a 0 5. (A) 3 log (B) 3 + log (C) 3 log (D) 3 + log. M benzoic acid (pk a 4.0) and M C 6 H 5 COONa solutions are given separately. What is the volume of benzoic acid required to prepare a 300 ml buffer solution of ph 4.5? [log 0.3] (A) 00 ml (B) 50 ml (C) 00 ml (D) 50 ml. What is the difference in ph for /3 and /3 stages of neutralisation of 0. M CH 3 COOH with 0. M NaOH. (A) log 3 (B) log (/4) (C) log (/3) (D) log IONIC EQUILIBRIUM_ADVANCED #

24 3. A weak acid (HA) after treatment with ml of 0. M strong base (BOH) has a ph of 5. At the end point, the volume of same base required is 7 ml. K a of acid is : (log 0.3) (A) (B) (C) (D) To prepare a buffer of ph 8.6 amount of (NH 4 ) to be added to 500 ml of 0.0 M NH 4 OH solution [pk a (NH 4+ ) 9.6] is : (A) 0.05 mole (B) 0.05 mole (C) 0.0 mole (D) mole 5. What fraction of an indicator Hln is in basic form at a ph of 6 if the pk a of the indicator is 5? (A) (B) 0 (C) (D) 0 6. An acid-base indicator which is a weak acid has a pk In value At what cocentration ratio of sodium acetate to acetic acid would the indicator show a colour half-way between those of its acid and conjugate base forms? [pk a of acetic acid 4.75, log 0.3] (A) 4 : (B) 6 : (C) 5 : (D) 3 : 7. Pure water is added into the following solutions causing a 0% increase in volume of each. The greatest % change in ph would be observed in which case (A), (B), (C) or (D)? (A) 0. M NaH (B) 0. M NaOH + (C) 0.3 M NH 3 0. M NH 4 system (D) 0.4 M CH 3 COONH 4 8. A well is dug in a bed of rock containing fluorspar (CaF ). If the well contains 0000 L of water, what is the amount of F in it? K sp 4 0 (0 /3.5) (A) 4.3 mol (B) 6.8 mol (C) 8.6 mol (D) 3.6 mol 9. What is the minimum ph when Fe(OH) 3 starts precipitating from a solution containing 0.M FeCl 3? K sp of Fe(OH) M 3 (A) 3.7 (B) 5.7 (C) 0.3 (D) The solubility product of AgCl is 0 0. The minimum volume (in L) of water required to dissolve.7 mg of AgCl is : (molecular weight of AgCl 43.5). (A) 0 lt. (B). lt. (C). lt. (D) 0 lt.. A solution prepared by dissolving.8 g of lime (CaO) in enough water to make.00 L of lime water (Ca(OH) (aq.)). If solubility of Ca(OH) in water is.48 gm/lt. The ph of the solution obtained will be : [log 0.3, Ca 40, O 6, H ] (A).3 (B).6 (C).3 (D) 3. At what molar concentration of HCl will its aqueous solution have an [H + ] to which equal contributions come from HCl and H O? (A) M (B) M (C) M (D) The best explanation for the solubility of MnS in dilute HCl is that : (A) Solubility product of MnCl is less than that of MnS. (B) Concentration of Mn + is lowered by the formation of complex ions with chloride ions. (C) Concentration of sulphide ions is lowered by oxidation to free sulphur. (D) Concentration of sulphide ions is lowered by formation of weak acid H S. 4. At 5ºC, the solubility product values of AgCl and AgCNS are.8 x 0 0 and.6 x 0 respectively. When a solution is saturated with both solids, calculate the ratio [Cl ] / [CNS ] and also [Ag + ] in the solution. (A).5, M (B).5, M (C).5, M (D).5, M 5. Arrange in increasing order of solubility of AgBr in the given solutions. (i) 0. M NH 3 (ii) 0. M AgNO 3 (iii) 0. M NaBr (iv) pure water (A) (iii) < (ii) < (iv) < (i) (B) (iii) < (ii) < (i) < (iv) (C) (iii) < (ii) (i) < (iv) (D) (ii) < (iii) < (iv) < (i) IONIC EQUILIBRIUM_ADVANCED # 3

25 One or More Than One Correct Type 6. Which is/are correct statements : (a) when 00 ml of 0. M NaCN solution is titrated with 0. M HCl solution the variation of ph of solution with volume of HCl added will be (as shown in figure): (b) variation of degree of dissociation with concentration for a weak electrolyte at a particular temperature is best represented by (as shown in figure) : (c) 0. M acetic acid solution is titrated against 0. M NaOH solution. The difference in ph between /4 and 3/4 stages of neutralization of acid will be log 3. (A) a & c (B) b & c (C) a, b & c (D) b only 7. Choose the correct statement : (A) ph of acidic buffer solution decrease if more salt is added. (B) ph of acidic buffer solution increases if more salt is added. (C) ph of basic buffer solution decreases if more salt is added. (D) ph of basic buffer solution increases if more salt is added. 8. Which of following can act as buffer? (A) NaCl + NaOH (C) NaH + Na H (B) Borax + Boric acid (D) NH 4 Cl + NH 4 OH. 9. Which of the following will show common ion effect and form a buffer solution? (A) CH 3 COONH 4 and CH 3 COOH (B) NH 4 Cl + NH 4 OH (C) H + NaH (D) NaCl + NaOH. 30. Which of the following solutions when added to L of a 0.0 M CH 3 COOH solution will cause no change in the degree of dissociation of CH 3 COOH and ph of the solution? K a for CH 3 COOH. (A) 0.6 mm HCOOH (K a ) (B) 0. M CH 3 COONa (C) 0.4 mm HCl (D) 0.0 M CH 3 COOH 3. Equal volumes of following solutions are mixed, in which case the ph of resulting solution will be average value of ph of two solutions? (A) aqueous HCl of ph, aqueous NaOH of ph. (B) aqueous HCl of ph, aqueous HCl of ph 4. (C) aqueous NaOH of ph, aqueous NaOH of ph 0. (D) aqueous CH 3 COOH of ph 5, aqueous NH 3 of ph 9. [K a (CH 3 COOH) K b (NH 3 )] IONIC EQUILIBRIUM_ADVANCED # 4

26 3. K a values for HA, HB and HD are 0-5, 0-7 and 0-9 respectively. Which of the following will be correct for decimolar aqueous solutions of NaA, NaB and NaD at 5 0 C? (A) (ph) NaA < (ph) NaB (B) (ph) NaD < (ph) NaB (C) (ph) NaA < (ph) NaD (D) (ph) NaB Which of the following are true for an acidbase titration? (A) Indicators catalyse the acid base reactions by releasing or accepting H + ions. (B) Indicators do not significantly affect the ph of the solution to which they are added. (C) Acidbase reactions do not occur in absence of indicators. (D) Indicators have different colours in dissociated and undissociated forms. 34. Let the colour of the indicator Hn (colourless) will be visible only when its ionised form (pink) is 5% or more in a solution. Suppose Hn (pk a 9.0) is added to a solution of ph 9.6 predict what will happen? (Take log 0.3) (A) Pink colour will be visible. (B) Pink colour will not be visible. (C) % of ionised form will be less than 5%. (D) % of ionised form will be more than 5%. 35. Which of the following mixtures will act as buffer? (A) H + NaOH (.5 : molar ratio) (B) H + NaOH (.5 : molar ratio) (C) NH 4 OH + HCl (5 : 4 molar ratio) (D) NH 4 OH + HCl (4 : 5 molar ratio) M CH 3 COOH is diluted at 5 C (K a ), then which of the following will be found correct? (A) [H + ] will increase. (B) ph will increase. (C) number of H + will increase. (D) all the above are correct. 37. Which of the following statements are correct at 5 C? (A) pk a for H 3 O + is 5.74 (B) pk b for OH is.74 (C) pk a + pk b pk w for HCl & ClOH (D) degree of dissociation of water is % PART - II : SUBJECTIVE QUESTIONS. Classify the following into acid, base and amphiprotic in terms of protonic concept. (i) H PO (ii) H PO 3 (iii) H (iv) HPO 3 (v) H + (vi) NH 4 + (vii) CH 3 COOH. Calculate [H + ], [HCOO ] and [OCN ] in a solution that contains 0.M HCOOH (K a.4 x 0-4 ) and 0. M HOCN (K a ). 3. A 0.5 M solution of pyridinium chloride, C 5 H 5 NH + Cl was found to have a ph of.75. What is K b for pyridine, C 5 H 5 N? (log 0.3) 4. Calculate the percentage hydrolysis & the ph of 0.0 M CH 3 COONH 4 : K b (NH 3 ).6 0 5, K a (CH 3 COOH) Calculate the degree of hydrolysis of M K CrO 4. K for H CrO 4. (It is essentially strong for first ionization). 6. What is the ph of 0.M NaH? K , K for carbonic acids. (Given : log 0.3, log ) 7. Calculate ph for : (i) 0.00 N NaOH, (ii) 0.0 N Ca(OH), (iii) 0.0 M Ca(OH) (iv) 0 8 M NaOH, (v) M Mg(OH). 8. Calculate the ph of the following solutions : (i). g of TlOH dissolved in water to give litre of solution. (ii) 0.37 g of Ca(OH) dissolved in water to give 500 ml of solution. (iii) 0.3 g of NaOH dissolved in water to give 00 ml of solution. (iv) ml of M HCl is diluted with water to give litre of solution. IONIC EQUILIBRIUM_ADVANCED # 5