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24) Consider the graph shown below and answer the following question. What part of the curve corresponds to the optimum buffer action of the acid/conjugate ion pair? Question 24-25.png 

4) The equilibrium constant (Ka) for the acid ionization of mercapto-ethanol (HS–CH2CH2–OH) is 1.91 x 10–10.      [H–SCH2CH2–OH(aq)       H+(aq)  +  –SCH2CH2OH (aq)     Ka = 1.91 x 10–10]       Which of the following statements is true regarding this equilibrium?The reaction is product favored.The reaction is reactant favored. Equilibrium lies far to the right. Equilibrium lies far to the left.

18) Which two equations illustrate water (H2O) acting as a proton donor? CH3COO – (aq) + H2O(l) → OH–(aq) + CH3COOH(aq) HNO3 (aq) + H2O(l)    → H3O+(aq) + NO3 – (aq)   2Na(s) + 2H2O(l)   → 2NaOH(aq)  + H2(g)     NH3 (g) + H2O(l)  → NH4OH(aq)

29) Consider the following reaction:                 N2(g) + O2(g)     2NO(g)Suppose we have a reaction mixture in which the initial concentration of [N2] is 0.20 M and the initial concentration of [O2] is 0.20 M. The Kc = 0.10. Find the equilibrium concentrations of N2, O2 and NO. To solve this problem, please use the I.C.E. table.

8) Consider the gas-phase equilibrium system represented by the equation:                                                                                               2H2O (g) + Heat      2H2(g) + O2(g)           [Hint = The reaction is Endothermic] Given that the forward reaction is endothermic, which of the following changes will decrease the equilibrium amount of H2O(g)?

22) Which of the following combinations cannot produce a buffer solution? HNO2 and NaNO2 HCN and NaCN HClO4 and NaClO4 NH3 and (NH4)2SO4

33) A solution made by dissolving 9.81 g of a nonvolatile nonelectrolyte in 90.0 g of water boiled at 100.37 o C at 760 mm Hg. What is the approximate molecular weight of the substance? (For water, Kb = 0.51 o C/m)    [DTb = Kb * m]                                                       

13) Consider the following reaction mechanism: Step1:  I–Cl  +   H2     →    H–I  +  HCl  (Slow)                                     Step 2:  I–Cl  +   H–I   →  HCl  +  I2     (Fast) The species HCl _________ while H–I _________________.

28) Complete the statement to give a correct answer. The stronger the acid, __________

16) If the rate law for the overall reaction [2A + 3B → Products] is first order in A and second order in B, then the rate law for this reaction is____