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2 Chem 16 Common arch 7, 008 Dr. Ellis NONE OF THE ULTIPLE CHOICE PROBLES REQUIRES EXTENSIVE OR TIE COSUING CALCULATIONS. IF YOUR ETHOD REQUIRES EXTENSTIVE CALCULATIONS IT IS EITHER WRONG OR HARDER THAN WHAT IS REQUIRED. 1. What is the equilibrium constant for the reaction: As Bg C(g)D(s), given that in a 5.00 L container A 0.5 moles, B 0.0 moles, C 0.5 moles, and D 0.1 moles at equilibrium? (a) 0.1 (b) mol 0.5mol [ C] ( ) (c) 1.5 [ B] ; [ C] ; K (d) 0.9 eq 5.0L 5.0L B (e) Some silicon dioxide, water, silane (SiH 4 ), and oxygen are at equilibrium in a sealed container at a particular temperature: SiO s H O g SiH g O g H > 0 4 In which of the following cases does the reaction NOT proceed to right to reestablish equilibrium? (a) Some silicon dioxide is added. (b) Some water vapor is added. (c) Some oxygen is removed. (d) The temperature is increased. (e) The volume of the container is increased.. All of the following compounds are soluble in water and are strong electrolytes except (a) NaI. (b) PbI. (c) Ca(CH COO). (d) NH 4 CH COO. (e) gcl. 4. The concentration of an HCl solution is 0.5. What is the ph? ph H (a) -1.8 (b) (c) 0 (d) 0.60 (e) 1.8 log log g of HI is dissolved in enough water to make a 0.00 L solution. What is the ph? (a) (b) (c) 1.5 (d) 0.75 (e) gHI 1mol HI HI x L 1 18gHI / Because HI is a strong acid it exists as H and I ions in solution. ph log H log Calculate the ph of a 4.4 x 10-5 barium hydroxide, Ba(OH), solution. (a) 4.05 (b) 9.95 (c) 4.5 (d) 9.65 (e) none of the above 5 poh log OH log 8.86x ph 14 poh 9.95

3 Chem 16 Common arch 7, 008 Dr. Ellis 7. The poh of a NaOH solution is What is the concentration of the OH - ion? (a) (b) 5.89x10-10 (c).40 x 10-5 (d) (e) 1.70x10-5 poh poh log OH. So, OH x10 8. What is the ph of a solution formed by mixing 5.0 ml of 0.66 HNO and 115 ml of 0.50 KOH? (a) 1.4 (b) 1.69 (c) 1.58 (d) 1.1 (e) none of the above 0.66mol 5mL mmol HNO x.1 mmol L 1 0.5mol 115mL mmol KOH x 8.75 mmol L 1 HNO aq KOH aq H O l KNO aq I.1 mmol 8.75 mmol C -.1 mmol -.1 mmol E mmol 5.65mmol poh log OH log 1.4; ph 14 poh mL 9. A solution consists of 0.75 phenol (C 6 H 5 OH, a weak acid, with K a 1.0 x10-10 ) and HNO. What is the ph? (a) 1.40 (b) 0.15 (c) 0.10 (d) 1.0 (e) none of the above ph log H log (strong acid weak acid; ignore weak acid) 10. A.6x10-4 aqueous solution of a weak acid, HB, has a ph of 6.0. Calculate K a, the acid-dissociation constant, for HB. (HB is some unknown weak acid. Its actual composition is irrelevant for solving the problem.) (a).6x10 - (b) 5.7x10-7 (c) 6.0x10-5 (d).4x10-9 (e) none of the above HB aq H aq B aq I x C x x x 4 E.6x10 x x x x H x HB x x ph ; x10 [ HB] 7 ( 9.x10 ) H B 9 Ka.4x x Which of the following solutions is neutral? (a) CH NH (aq) (b) CsI(aq) (c) KCH COO(aq) (d) HCOOH(aq) (e) FeCl (aq)

4 Chem 16 Common arch 7, 008 Dr. Ellis 1. For the reaction: NH ( aq) CH COOH ( aq) NH ( aq ) CH COO ( aq) ", what is the conjugate base? 4 (a) NH (b) CH COOH (c) NH 4 (d) CH COO - (e) OH - 1. Which of the following solutions has the highest solubility for iron (III) hydroxide? (a) pure water (b) water buffered to a ph of Le Chatelier s Principle: (c) water buffered to a ph of 5 It is most soluble in the solution with the lowest [OH - ] (d) water buffered to a ph of 10 because stress is too little [OH - ] (e) water buffered to a ph of What is the concentration of a 5.00 L HBr solution if 0.0 ml of it is completely neutralized by 95.7 ml 0.5 NaOH? (a) (b) (c) 0.50 (d) (e) NaOH aq HBr aq H O l NaBr aq 0.5mol NaOH 95.7mL NaOH 1mmol HBr x x.9mmol HBr L 1 1mmol NaOH.9mmol HBr mol HBr 0mL L 15. In which of the following reactions does the underlined compound act as a Lewis base? I. NH aq H O l NH aq OH aq 4 II. NH aq H O l NH aq H O aq 4 III. NH Ga OH NH Ga OH where the N is bonded to the Ga (a) only I (b) only II (c) only III (d) II and III (e) I, II, and III 16. Calculate the ph of a solution that is 0.1 in HF and 1.4 KF. (HF: K a 6.76 x 10-4 ) (a) 0.68 (b) 1.9 (c) 4.00 (d).17 (e).4 4 pk log K log 6.76 x a a B o 1.4 ph pka log.17 log 4.00 [ HB] 0.1 o

5 Chem 16 Spring 007 Common arch 9 Dr. Ellis PROBLES (1 points each; 6 total) I. The K a for Chlorous acid, HClO, is 1.15 x (a) (4 PT) What is the [H ] for a 0.85 solution of this acid? Show work, including an ICE table. Use method of successive approximation for full credit. I HClO aq H aq ClO aq C x x x E 0.85 x x x H ClO x 1.15x x [ HClO ] x x x (first iteration with x 0) H 0.09 nd ( iteration) rd th 0.09 ( and 4 iteration ) (b) (4 PT) What is the percent dissociation of chlorous acid? Percent dissociation x [ HClO ] o 0.09 x100% x100% 11% 0.85 (c) (4 PT) What happens to the percent dissociation as the solution of chlorous acid is diluted by the addition of water? Why? (Circle correct choice and give reason.) -It decrease because -It stays the same because -It increases because dilution stress too few species in solution; reaction moves to make more species (using Le Chatelier s principle)

6 Chem 16 Spring 007 Common arch 9 Dr. Ellis II. Separation of ions by precipitation. A solution contains 0.0 AgNO and 0.50 Ca(ClO 4 ). Sodium carbonate will be added to the solution. The K sp for silver carbonate is 8.5 x The K sp for calcium carbonate is 5 x (a) ( PT) Write the equation for the dissolution of Ag CO, (Include (s) and (aq) and charge on ions) Ag CO s Ag aq CO aq (b) ( PT) Write the solubility product expression for the dissolution of silver carbonate (K sp?): 1 sp Ag CO K x (c) ( PT) At what carbonate concentration does silver carbonate start to precipitate? 1 K sp 8.5x10 11 CO 9.4x10 Ag ( 0. ) (d) ( PT) At what carbonate concentration does calcium carbonate start to precipitate? Hint, first do steps (a) and (b) above. CaCO s Ca aq CO aq Ca CO K x 9 sp K sp 510 x 8 CO 1.0x10 Ca 0.5 (e) ( PT) As the carbonate ion concentration increases, what compound is the first to precipitate? Why? Silver carbonate because it starts to precipitate at a smaller carbonate conc. (9.4 x10-11 is smaller than 1x10-8 ). (f) ( PT) For the compound which precipitates first, what is the concentration of its remaining ions when the second compound begins to precipitate? K sp K sp 8.5x10 8 CO 110 x CO Ag Ag 0.09

7 I Chem 16 Spring 007 Common arch 9 Dr. Ellis III (a) (6 PT) What is the ph of a potassium cyanide, KCN, solution? For HCN, the K a is 4.79 x Include (i) writing the reaction (the net ionic reaction, that is, what takes place when KCN is added to water), (ii) finding the value of its equilibrium constant (K b ), and (iii) setting up the ICE table. K 10 CN aq H O l HCN aq OH aq K x 14 w 5 b Ka 4.79x C x x x E x HCN OH x.09x10 CN x x 5.09x x 5 x poh log ph (b) (6 PT) What is the solubility of copper (II) phosphate in a 0.5 solution of Cu(NO ). The K sp is 1.4 x Include (i) writing the reaction for the dissolution of copper (II) phosphate, (ii) setting up an ICE table, and (iii) writing the solubility product expression (K sp?). Cu PO s Cu aq PO aq K 1.4x10 I excess sp C x x x E excess 0.5 x x Note that x is the solubility Cu PO x x x 7 x must be very close to 0 because 1.4x10 is so small. Thus, x 1.4x10 ; x 7 1.4x10 9.0x10 mol/ L