T8-1P1 [212 marks] 1. Which is an acid-base conjugate pair? A. H3 O / OH B. H2SO 4 / SO4 C. CH3COOH / H3 O D. CH3NH 3 + / CH3NH2 2. Which of the following is correct? A. A weak acid is a proton donor and its aqueous solution shows good conductivity. B. A weak acid is a proton donor and its aqueous solution shows poor conductivity. C. A weak acid is a proton acceptor and its aqueous solution shows good conductivity. D. A weak acid is a proton acceptor and its aqueous solution shows poor conductivity. 3. Which species produced by the successive dissociations of phosphoric acid, H3PO 4, are amphiprotic? A. HPO 4 2 and PO4 B. H2PO 4 and HPO4 C. H2PO 4 and PO4 D. HPO 4 2 only 4. Which species acts as a Lewis and Brønsted Lowry base? A. [Al(H2O) 6] 3+ B. BF3 C. NH4 D. OH Soluble acids and bases ionize in water. Sodium hypochlorite ionizes in water. OCl (aq) + H2O(l) OH (aq) + HOCl(aq) 5a. Identify the amphiprotic species.
5b. Identify one conjugate acid-base pair in the reaction. A solution containing 0.510 g of an unknown monoprotic acid, HA, was titrated with 0.100 mol dm 3 NaOH(aq). 25.0 cm 3 was required to reach the equivalence point. 5c. Calculate the amount, in mol, of NaOH(aq) used. 5d. Calculate the molar mass of the acid. 5e. Calculate [H + ] in the NaOH solution. 6. Which is a conjugate Brønsted Lowry acid-base pair? A. CH COO 3 / H3 O + B. H O / CH COO 2 3 C. H2O / H3 O + D. CH3COOH / H2O
7. Which species behave as Brønsted Lowry bases in the following reaction? H2SO 4 + HNO 3 H2NO 3 + + HSO4 - A. HNO 3 and HSO4 - B. HNO 3 and H2NO 3 + C. H2SO 4 and HSO 4 - D. H2NO 3 + and HSO4 - Phosphine (IUPAC name phosphane) is a hydride of phosphorus, with the formula PH 3. 8a. (i) Draw a Lewis (electron dot) structure of phosphine. (ii) Outline whether you expect the bonds in phosphine to be polar or non-polar, giving a brief reason. (iii) Explain why the phosphine molecule is not planar. [6 marks] (iv) Phosphine has a much greater molar mass than ammonia. Explain why phosphine has a significantly lower boiling point than ammonia.
8b. Phosphine is usually prepared by heating white phosphorus, one of the allotropes of phosphorus, with concentrated aqueous sodium hydroxide. The equation for the reaction is: [10 marks] P4 (s) + 3OH (aq) + 3H2O (l) PH 3 (g) + 3H2PO 2 (aq) (i) Identify one other element that has allotropes and list two of its allotropes. Element: Allotrope 1: Allotrope 2: (ii) The first reagent is written as P 4, not 4P. Describe the difference between P 4 and 4P. (iii) The ion H2PO 2 is amphiprotic. Outline what is meant by amphiprotic, giving the formulas of both species it is converted to when it behaves in this manner. (iv) State the oxidation state of phosphorus in P 4 and H2PO 2. P 4: H2PO 2 : (v) Oxidation is now defined in terms of change of oxidation number. Explore how earlier definitions of oxidation and reduction may have led to conflicting answers for the conversion of P 4 to H2PO 2 and the way in which the use of oxidation numbers has resolved this.
2.478 g of white phosphorus was used to make phosphine according to the equation: 8c. P (s) +3OH 4 (aq)+3h2o(l) PH 3(g)+3H2PO 2 (aq) [4 marks] (i) Calculate the amount, in mol, of white phosphorus used. (ii) This phosphorus was reacted with 100.0 cm 3 of 5.00 mol dm 3 aqueous sodium hydroxide. Deduce, showing your working, which was the limiting reagent. (iii) Determine the excess amount, in mol, of the other reagent. (iv) Determine the volume of phosphine, measured in cm 3 at standard temperature and pressure, that was produced.
Phosphine (IUPAC name phosphane) is a hydride of phosphorus, with the formula PH 3. 9a. (i) Draw a Lewis (electron dot) structure of phosphine. (ii) State the hybridization of the phosphorus atom in phosphine. [8 marks] (iii) Deduce, giving your reason, whether phosphine would act as a Lewis acid, a Lewis base, or neither. (iv) Outline whether you expect the bonds in phosphine to be polar or non-polar, giving a brief reason. (v) Phosphine has a much greater molar mass than ammonia. Explain why phosphine has a significantly lower boiling point than ammonia. (vi) Ammonia acts as a weak Brønsted Lowry base when dissolved in water. Outline what is meant by the terms weak and Brønsted Lowry base. Weak: Brønsted Lowry base:
9b. Phosphine is usually prepared by heating white phosphorus, one of the allotropes of phosphorus, with concentrated aqueous sodium hydroxide. The equation for the reaction is: [8 marks] (i) The first reagent is written as P 4, not 4P. Describe the difference between P 4 and 4P. (ii) The ion H2PO 2 is amphiprotic. Outline what is meant by amphiprotic, giving the formulas of both species it is converted to when it behaves in this manner. (iii) State the oxidation state of phosphorus in P 4 and H2PO 2. P 4: H2PO 2 : (iv) Oxidation is now defined in terms of change of oxidation number. Explore how earlier definitions of oxidation and reduction may have led to conflicting answers for the conversion of P 4 to H2PO 2 and the way in which the use of oxidation numbers has resolved this.
9c. 2.478 g of white phosphorus was used to make phosphine according to the equation: [4 marks] (i) Calculate the amount, in mol, of white phosphorus used. (ii) This phosphorus was reacted with 100.0 cm 3 of 5.00 mol dm 3 aqueous sodium hydroxide. Deduce, showing your working, which was the limiting reagent. (iii) Determine the excess amount, in mol, of the other reagent. (iv) Determine the volume of phosphine, measured in cm 3 at standard temperature and pressure, that was produced.
Impurities cause phosphine to ignite spontaneously in air to form an oxide of phosphorus and water. 9d. (i) 200.0 g of air was heated by the energy from the complete combustion of 1.00 mol phosphine. Calculate the temperature rise using section 1 of the data booklet and the data below. [9 marks] Standard enthalpy of combustion of phosphine, Specific heat capacity of air = 1.00Jg 1K 1=1.00kJkg 1K 1 (ii) The oxide formed in the reaction with air contains 43.6% phosphorus by mass. Determine the empirical formula of the oxide, showing your method. (iii) The molar mass of the oxide is approximately 285 g mol 1. Determine the molecular formula of the oxide. (iv) State the equation for the reaction of this oxide of phosphorus with water. (v) Suggest why oxides of phosphorus are not major contributors to acid deposition. (vi) The levels of sulfur dioxide, a major contributor to acid deposition, can be minimized by either pre-combustion and post-combustion methods. Outline one technique of each method. Pre-combustion: Post-combustion: Across period 3, elements increase in atomic number, decrease in atomic radius and increase in electronegativity. 10a. Define the term electronegativity.
10b. Explain why the atomic radius of elements decreases across the period. 10c. State the equations for the reactions of sodium oxide with water and phosphorus(v) oxide with water. 10d. Suggest the ph of the solutions formed in part (c) (i).
10e. Describe three tests that can be carried out in the laboratory, and the expected results, to distinguish between 0.10 moldm 3 HCl(aq) and 0.10 moldm 3 CH 3 COOH(aq). [3 marks] 10f. Explain whether BF can act as a Brønsted-Lowry acid, a Lewis acid or both. 3 Describe the bonding and structure of sodium chloride. 10g.
10h. State the formula of the compounds formed between the elements below. Sodium and sulfur: Magnesium and phosphorus: 10i. Covalent bonds form when phosphorus reacts with chlorine to form PCl 3. Deduce the Lewis (electron dot) structure, the shape and [4 marks] bond angle in PCl 3 and explain why the molecule is polar. Lewis (electron dot) structure: Name of shape: Bond angle: Explanation of polarity of molecule: When nitrogen gas and hydrogen gas are allowed to react in a closed container, the following equilibrium is established. N 2 (g) + 3H 2 (g) 2NH 3 (g) ΔH = 92.6 kj Outline two characteristics of a reversible reaction in a state of dynamic equilibrium. 11a.
Deduce the equilibrium constant expression, K, for the reaction. 11b. c Predict, with a reason, how each of the following changes affects the position of equilibrium. 11c. The volume of the container is increased. Ammonia is removed from the equilibrium mixture. 11d. Define the term activation energy, E a. Ammonia is manufactured by the Haber process in which iron is used as a catalyst. Explain the effect of a catalyst on the rate of 11e. reaction.
Sketch the Maxwell Boltzmann energy distribution curve for a reaction, labelling both axes and showing the activation energy with 11f. and without a catalyst. Typical conditions used in the Haber process are 500 C and 200 atm, resulting in approximately 15% yield of ammonia. 11g. [3 marks] (i) Explain why a temperature lower than 500 C is not used. (ii) Outline why a pressure higher than 200 atm is not often used. Define the term base according to the Lewis theory. 11h. 11i. Define the term weak base according to the Brønsted-Lowry theory.
Deduce the formulas of conjugate acid-base pairs in the reaction below. 11j. CH 3 NH 2 (aq) + H 2 O(l) CH 3 NH + 3 (aq) + OH (aq) Outline an experiment and its results which could be used to distinguish between a strong base and a weak base. 11k. [3 marks] This question is about the compounds of some period 3 elements. State the equations for the reactions of sodium oxide with water and phosphorus(v) oxide with water. 12a. Explain why the melting point of phosphorus(v) oxide is lower than that of sodium oxide in terms of their bonding and structure. 12b.
12c. Predict whether phosphorus(v) oxide and sodium oxide conduct electricity in their solid and molten states. Complete the boxes with yes or no. Predict and explain the ph of the following aqueous solutions, using equations to support your answer. 12d. Ammonium chloride, NH 4 Cl(aq) : [4 marks] Sodium methanoate, HCOONa(aq) :
Acids can be described as strong or weak. 13a. (i) Outline the difference in dissociation between strong and weak acids of the same concentration. [4 marks] (ii) Describe three tests that can be carried out in the laboratory, and the expected results, to distinguish between 0.10 moldm 3 HCl(aq) and 0.10 moldm 3 CH 3 COOH(aq).
Calculate the ph, using table 15 of the data booklet, of a solution of ethanoic acid made by dissolving 1.40 g of the acid in distilled [4 marks] 13b. water to make a 500 cm 3 solution.
13c. Determine the ph at the equivalence point of the titration and the pk a of an unknown acid using the acid-base titration curve below. [3 marks] Identify, using table 16 of the data booklet, a suitable indicator to show the end-point of this titration. 13d.
Describe how an indicator, that is a weak acid, works. Use Le Chatelier s principle in your answer. 13e. 13f. State the formula of the conjugate base of chloroethanoic acid, CH 2 ClCOOH. 13g. Determine the ph of the solution resulting when 100 cm 3 of 0.50 moldm 3 CH 2 ClCOOH is mixed with 200 cm 3 of 0.10 moldm 3 NaOH. [4 marks]
Describe how chlorine s position in the periodic table is related to its electron arrangement. 13h. SCl and are two sulfur chloride type compounds with sulfur having different oxidation states. Predict the name of the shape, the bond 13i. 2 SClF 5 angle and polarity of these molecules. When nitrogen gas and hydrogen gas are allowed to react in a closed container the following equilibrium is established. N 2 (g) + 3H 2 (g) 2NH 3 (g) ΔH = 92.6 kj Outline two characteristics of a reversible reaction in a state of dynamic equilibrium. 14a.
Predict, with a reason, how each of the following changes affects the position of equilibrium. 14b. The volume of the container is increased. Ammonia is removed from the equilibrium mixture. 14c. Define the term activation energy, E a. Ammonia is manufactured by the Haber process in which iron is used as a catalyst. 14d. Explain the effect of a catalyst on the rate of reaction.
Typical conditions used in the Haber process are 500 C and 200 atm, resulting in approximately 15% yield of ammonia. 14e. (i) Explain why a temperature lower than 500 C is not used. [3 marks] (ii) Outline why a pressure higher than 200 atm is not often used. 14f. Deduce the equilibrium constant expression, K c, for the reaction on page 10. 14g. When 1.00 mol of nitrogen and 3.00 mol of hydrogen were allowed to reach equilibrium in a 1.00 dm 3 container at a temperature of 500 C and a pressure of 1000 atm, the equilibrium mixture contained 1.46 mol of ammonia. Calculate the value of K c at 500 C. Define the term base according to the Lewis theory. 14h.
Define the term weak base according to the Brønsted Lowry theory. 14i. 14j. Deduce the formulas of conjugate acid-base pairs in the reaction below. CH 3 NH 2 (aq) + H 2 O(l) CH 3 NH + 3 (aq) + OH (aq) (i) Sketch the ph titration curve obtained when 50.0 cm of is added to of 14k. 3 0.100 moldm 3 NH 3 (aq) 25.0 cm 3 0.100 moldm 3 HCl (aq). [4 marks] (ii) Identify an indicator from table 16 of the data booklet that could be used for this titration.
15. Which are acid-base pairs according to the Brønsted Lowry theory? I. HNO 3 /NO 3 II. H 3 O + /OH III. HCOOH/HCOO A. I and II only B. I and III only C. II and III only D. I, II and III 16. What is the conjugate base of phenol, C 6 H 5 OH? A. C 6 H OH 4 B. + C 6 H 5 OH2 C. C 6 H 5 O D. C 6 H + 6 OH A sample of magnesium contains three isotopes: magnesium-24, magnesium-25 and magnesium-26, with abundances of 77.44%, 10.00% and 12.56% respectively. Calculate the relative atomic mass of this sample of magnesium correct to two decimal places. 17a. Predict the relative atomic radii of the three magnesium isotopes, giving your reasons. 17b.
17c. Describe the bonding in magnesium. State an equation for the reaction of magnesium oxide with water. 17d. Phosphorus(V) oxide, P 4 O 10 (M r = 283.88), reacts vigorously with water (M r = 18.02), according to the equation below. P 4 O 10 (s) + 6H 2 O(l) 4H 3 PO 4 (aq) A student added 5.00 g of P to 1.50 g of water. Determine the limiting reactant, showing your working. 17e. 4 O 10 Calculate the mass of phosphoric(v) acid, H, formed in the reaction. 17f. 3 PO 4
State a balanced equation for the reaction of aqueous H with excess aqueous sodium hydroxide, including state symbols. 17g. 3 PO 4 17h. State the formula of the conjugate base of H 3 PO 4. (i) Deduce the Lewis structure of PH. 17i. + 4 [4 marks] (ii) Predict, giving a reason, the bond angle around the phosphorus atom in PH +. 4 (iii) Predict whether or not the P H bond is polar, giving a reason for your choice.
Consider the following list of organic compounds. Compound 1: CH 3 CH 2 CH(OH)CH 3 Compound 2: CH 3 CH 2 COCH 3 Compound 3: CH 3 CH 2 CH 2 OH Compound 4: CH 3 CH 2 CH 2 CHO Apply IUPAC rules to state the names of the four compounds. 18a. [4 marks] (i) 18b. Define the term structural isomers. (ii) Identify the two compounds in the list that are structural isomers of each other.
(i) Determine the organic product formed when each of the compounds is heated under reflux with excess acidified potassium 18c. dichromate(vi). If no reaction occurs write NO REACTION in the table. [5 marks] (ii) Describe the colour change during the reactions that occur in part (i). (i) Pentanoic acid reacts with ethanol. State the structural formula of the organic product and the name of the functional group it [3 marks] 18d. contains. (ii) State the type of reaction in part (i).
Describe what is meant by a weak Brønsted-Lowry base, including an equation for the reaction of ammonia with water. 18e. [3 marks] 19. What are the conjugate acid base pairs in the following reaction? HCO 3 (aq) + H 2 O(l) OH (aq) + H 2 CO 3 (aq) 20. What are the conjugate acid base pairs in the following reaction? HCO 3 (aq) + H 2 O(l) OH (aq) + H 2 CO 3 (aq) 21. Which of the following is an example of a Lewis acid base reaction, but not a Brønsted Lowry acid base reaction? A. B. C. D. 2CrO 2 4 (aq) + 2H+ (aq) Cr 2 O 2 7 (aq) + H 2 O(l) Co(H 2 O) 2+ 6 (aq) + 4HCl(aq) CoCl 2 4 (aq) + 4H+ (aq) + 6H 2 O(l) NH 3 (aq) + H + (aq) NH + 4 (aq) CH 3 COO (aq) + H 2 O(l) CH 3 COOH(aq) + OH (aq) In acidic solution, ions containing titanium can react according to the half-equation below. TiO 2+ (aq) + 2H + (aq) + e Ti 3+ (aq) + H 2 O(l) 22a. State the initial and final oxidation numbers of titanium and hence deduce whether it is oxidized or reduced in this change.
22b. Considering the above equilibrium, predict, giving a reason, how adding more acid would affect the strength of the TiO 2+ ion as an oxidizing agent. A reactivity series comparing titanium, cadmium and europium is given below. Least reactive Cd < Ti < Eu Most reactive The half-equations corresponding to these metals are: Eu 2+ (aq) + 2e Eu(s) Ti 3+ (aq) + 3e Ti(s) Cd 2+ (aq) + 2e Cd(s) 22c. Deduce which of the species would react with titanium metal. Deduce the balanced equation for this reaction. 22d. Deduce which of the six species is the strongest oxidizing agent. 22e.
A voltaic cell can be constructed using cadmium and europium half-cells. State how the two solutions involved should be connected 22f. and outline how this connection works. Some students were provided with a 0.100 moldm 3 solution of a monobasic acid, HQ, and given the problem of determining whether HQ was a weak acid or a strong acid. Define a Brønsted Lowry acid. 22g. Distinguish between the terms strong acid and weak acid. 22h. Neelu and Charles decided to solve the problem by determining the volume of 0.100 moldm sodium hydroxide solution needed 22i. 3 to neutralize 25.0 cm 3 of the acid. Outline whether this was a good choice.
Neelu and Charles decided to compare the volume of sodium hydroxide solution needed with those required by known 22j. 0.100 moldm 3 strong and weak acids. Unfortunately they chose sulfuric acid as the strong acid. Outline why this was an unsuitable choice. 22k. State a suitable choice for both the strong acid and the weak acid. Strong acid: Weak acid: 22l. Francisco and Shamiso decided to measure the ph of the initial solution, HQ, and they found that its ph was 3.7. Deduce, giving a reason, the strength (weak or strong) of the acid HQ. Suggest a method, other than those mentioned above, that could be used to solve the problem and outline how the results would 22m. distinguish between a strong acid and a weak acid. International Baccalaureate Organization 2017 International Baccalaureate - Baccalauréat International - Bachillerato Internacional Printed for BLUPS