DO NOT WRITE IN THIS SECTION Marker Date marked Points Q1: /32 Q2: /26 Q3: /22 TOTAL :
Name Section number Chemistry 130 (1,2) Dr. J. F. C. Turner Quiz 2 30 minutes Please answer all parts of all questions and show all your work You may use: Non-programmable calculators You may not use: Any written materials (cards or notes etc) or any electronic device 1.(a) Write down the relationship between the change in standard Gibbs function, G° , and the equilibrium constant, K eq 2 points
(b) Write down the relationship between K c and K p for a gas phase reaction.
2 points
(c) The reaction between diborane, B2 H6 g and iodine, I2g results in boron triiodide, BI 3 g and hydrogen iodide, HI g , according the the equation B2 H6 g 6I2 g 2BI 3 g 6 HI g . The equilibrium constant K c for this 6 1 1 reaction is given by K c = 2.04 ×10 at 298 K . Given that R=8.314 J mol K , calculate the value of K p for this reaction.
6 points (d) Write down a definition of Le Châtelier's Principle.
4 points (e) If the reaction between diborane and iodine in part (c) is subject to an increase in pressure, predict the change, if any, in the concentrations of the reactants and products.
4 points
(f) Write down the Van't Hoff equation that relates the equilibrium constant K1 at temperature T 1 to the equilibrium constant K2 at temperature T 2 .
4 points 6 (g) The equilibrium constant for the reaction B2 H6 g 6I2 g 2BI 3 g 6 HI g is given by K c = 2.04 ×10 at 298 K . Given that H° = 264.8 kJ mol 1 and R=8.314 J mol 1 K 1 , calculate the equilibrium constant at 500 K .
6 points (h) Explain how your result from (g) is consistent with Le Châtelier's Principle.
4 points 32 points
2.(a) Write down the relationship between the acid constant, K A , of an acid and the base constant, K B , of its conjugate base.
4 points
(b) Write down the relationship between pH , pOH and p KW
2 points (c) Write down the balanced equilibrium associated with the autoprotolysis of water, paying careful attention to the states and charges, together with the numerical value of the equilibrium constant, KW
K W = 4 points 1 (d) A 1 mol L solution of hypoiodous acid, HOI aq is prepared. Write down the balanced acid equilibrium for this acid, including states and charges.
4 points 11 (e) Hypoiodous acid is a weak acid with an acid constant of K A HOI aq =1×10 . Calculate the pH and the concentration of hydroxide ion in a 1 mol L 1 solution.
p H = [ OH aq ] = 6 points (f) Write down the relationship between pH , pOH and pKW
2 points (g) Calculate the base constant for the hypoiodite ion, OI aq
4 points 26 points
3(a) Write a balanced equilibrium that for the dissolution of silver phosphate, Ag 3 PO 4 s , which is a sparingly soluble salt, paying careful attention to the charges and states for all the species present.
4 points (b) Calculate the concentration of silver ion and phosphate ion in an aqueous solution that is in equilibrium with 17 Ag 3 PO 4s , given that K sp Ag 3 PO 4 s = 8.89 ×10 .
3 [ Ag aq ] = [ PO 4 aq ] = 6 points (c) Is the solution in (b) a dynamic or static equilibrium? Underline your answer static dynamic 2 points ° 1 1 (d) Calculate G sol for Ag 3 PO 4 s at 298 K given that R=8.314 J mol K .
4 points 1 (e) 5 mL of a 0.05 mol L solution of Na 3 PO 4aq is added to the solution in (b). Calculate the new concentration of silver ion that is present in solution after the addition.
6 points 22 points