Acid Dissociation Constant and Acetic Acid

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CHM1022 Tutorial 2 – Semester 2, 2012

(Chemical Equilibria)

1. The reaction 2 HCl(g) +I2(s) [pic] 2 HI (g) + Cl2(g) has Kc = 1.0 x 10-34 at 25˚C. If a 1.00 L reaction vessel initially contains 0.100 mol of each HCl and solid I2, what are the concentrations of HI and Cl2 at equilibrium? 2. Consider the following gas-phase reaction and equilibrium constant at 25 oC:

4 HCl(g) + O2(g) [pic] 2 Cl2(g) + 2 H2O(g) The concentrations of all species were measured at a particular moment in time and the following data were obtained: [HCl] = 0.00050 M; [O2] = 0.0010 M; [Cl2] = 2.30 M; [H2O] = 1.22 M Do these concentrations represent equilibrium concentrations? Which way the reaction will proceed? [Hint: Calculate the reaction quotient]

3. What is the pH of a 1.0 molar solution of acetic acid? (Ka acetic acid = 1.8x10-5)

4. Pyridine is a very common weak base used as solvent in organic synthesis.

C5H5N(aq) + H2O(l) ⇌ C5H5NH+(aq) + OH-(aq)

Assume you have 0.0213 M aqueous solution of pyridine, C5H5N. The pKb value for the pyridine is 8.77. (a) What is the concentration of OH- in this solution?
(b) What is the pH of the solution?

5. A solution is prepared from 0.0250 mole of HCl, 0.10 mole propanoic acid, C2H5COOH, and enough water to make 0.500 liter of solution. Determine the concentrations of H3O+, C2H5COOH, C2H5COO-, and OH- in this solution. (pKa for propanoic acid = 4.89)

6. If the solubility of Ag2Cr2O7 is 6.5 × 10-5 mol/L, determine the solubility product for this salt. What is the solubility in 0.01 M AgNO3?
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