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BCIT Winter 2015 Chem 0012 Exam #2 Name: ___________________ Attempt all questions in this exam. Read each question carefully and give a complete answer in the space provided. Part marks given for wrong answers with partially correct reasoning/calculations. Constants and equations are attached at the back. Data sheets and tables are provided. Total points = 30 Page 1 of 7
Section I: Multiple choice (15 points total, 1 point each) Choose the BEST answer to the following questions. 1. The solubility of a solute is best determined from which type of solution? a. a saturated solution b. any solution at 25°C c. an unsaturated solution d. a supersaturated solution 2. Which equation represents the reaction between 0.2 M Na2CO3 and 0.2 M Ba(NO3)2? a. Na+(aq) + NO3⁻(aq)  NaNO3(s) b. Ba2+(aq) + CO3²⁻(aq)  BaCO3(s) c. Na2CO3(s)  2Na+(aq) + CO3²⁻(aq) d. Ba(NO3)2(s)  Ba²+(aq) + 2NO3⁻(aq) 3. Which compound will have the lowest molar solubility? a. BeS b. FeS c. ZnS d. Cs2S 4. Which relationship can be used to calculate the maximum [Ba2+] that can exist in a solution of Ba3(PO4)2? a.
b.
c.
d.
5. What is the maximum [Pb2+] possible in a 0.10 M NaCl solution? a. 1.2x10‐5 M b. 6.0x10‐5 M c. 1.2x10‐3 M d. 3.0x10‐3 M Page 2 of 7
6. What is the conjugate acid of the base HAsO4²⁻? a. AsO4³⁻ b. H2AsO4²⁻ c. H2AsO4⁻ d. H3AsO4 7. The following equilibrium favours the formation of products: NH2OH + CH3NH3+ ⇌CH3NH2 + NH3OH+ Which is the strongest acid? a. NH3OH+ b. NH2OH c. CH3NH2 d. CH3NH3+ 8. The S²⁻ ion is a base with a Kb value of 0.77. What is the Ka value for HS⁻? a. 1.3x10‐14 b. 9.1x10‐8 c. 1.1x10‐7 d. 7.7x1013 9. Which equation best describes the interaction of a weak base with water? a. NaOH(aq) → Na+(aq) + OH⁻(aq) b. CH3CH2OH () →CH3CH2OH(aq) c. H2PO4²⁻ (aq) + H2O() ⇌PO4³⁻(aq) + H3O+(aq) d. N2H4(aq) + H2O() ⇌ N2H5+(aq) + OH⁻(aq) 10. What is the Ka expression for H3PO4? a.
b.
c.
d.
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11. What is the predominant net ionic equation for the hydrolysis of (NH4)2HPO4? a. NH4+(aq) + H2O() ⇌ H3O+(aq) + NH3(aq) b. HPO4²⁻ (aq) + H2O() ⇌ H3O+(aq) + PO43⁻(aq) c. (NH4)2HPO4(aq) + H2O() ⇌ 2NH4+(aq) + HPO4²⁻(aq) d. HPO4²⁻(aq) + H2O() ⇌ OH⁻(aq) + H2PO4⁻(aq) 12. Which of the following salt solutions is acidic? a. KBr b. FeCl3 c. Li2C2O4 d. NaHCO3 13. Which of the following could be used to prepare a buffer solution? a. NaHC2O4 and Na2C2O4 b. Na2C2O4 and NaOH c. HNO3 and NaNO3 d. HNO3 and NaOH 14. What is the oxidation number of O in Na2O2? a. ‐2 b. ‐1 c. +1 d. +2 15. Consider the following reaction: Co + SO4²⁻ + 4H+ → Co2+ + H2SO3 + H2O Which statement is correct? a. The sulphur is oxidzed and the cobalt is reduced. b. The cobalt is oxidzed and the sulfur is reduced. c. The cobalt is oxidzed and the hydrogen is reduced. d. The oxygen is oxidzed and the hydrogen is reduced. Page 4 of 7
Section II: Written problems (15 points total). 16. The solubility of Zn(OH)2 in pure water is 4.2x10‐6 M. What is the value of Ksp for Zn(OH)2? (3 points) 17. a) Write the net ionic equation for the reaction between aqueous Pb(NO3)2 and aqueous NaCl. (1 point) b) Show with calculations whether a precipitate will form when 15.0 mL of 0.050 M Pb(NO3)2 is added to 35.0 mL of 0.085 M NaCl. (4 points) Page 5 of 7
18. What is the pH of a 0.50 M HF solution? (4 points) 19. Balance the following redox reaction in acidic solution: (3 points) Sb + NO3ˉ  Sb2O5 + NO Page 6 of 7
Equations and Constants pH = ‐log[H⁺] pOH = ‐log[OHˉ] pH + pOH = 14.00 at 25°C Kw = 1.0x10‐14 at 25°C Kw = Ka Kb pX = ‐log(X) [H⁺] = 10‐pH [OHˉ] = 10‐pOH X = 10‐pX  
 A 

pH  pK a  log
 HA 
The solution to the quadratic equation ax² + bx +c =0 is √
4
2
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