Chapter 8(1)(2).docx

Chapter 8 Acid and Base Score /41 Name: Class: 1. This question is all about buffer solution calculations :) *buffered: an aqueous solution consisting of a mixture of a weak acid and its conjugate base, or vice versa. unbuffered: an aqueous solution consisting of only acid/base and water. a. Calculate the pH of an unbuffered 0.010M acetic acid (CH3COOH) solution.

(Ka=1.8x10-5) [1]

b. Calculate the pH of a buffered 0.010M ideal acetic acid solution. [2]

c. Calculate the pH of an unbuffered 0.010M acetic acid solution in which 0.004 M of H+ is being added from an acidic source. [2]

d. Calculate the pH of an unbuffered 0.010M acetic acid solution in which 0.004 M of OH- is being added from a basic source. [2]

2. A buffer solution is made from 30.0 cm3 of 0.500 moldm-3 NaOH and 20 cm3 of 1.500 moldm-3 CH3COOH. Calculate the pH of the buffer solution at 298K. (pKa (CH3COOH) = 4.76) [4]

2. Limescale, CaCO3(s), can be removed from water kettles by using vinegar, a dilute solution of ethanoic acid, CH3COOH(aq). a. Predict, giving a reason, a difference between the reactions of the same concentrations of hydrochloric acid and ethanoic acid with samples of calcium carbonate. [2]

b. Dissolved carbon dioxide causes unpolluted rain to have a pH of approximately 5.6, but other dissolved gases can result in a much lower pH. State one environmental effect of acid rain. [1]

c. Write an equation to show ammonia, NH3, acting as a Brønsted–Lowry base and a different equation to show it acting as a Lewis base. [2]

d. Explain, using appropriate equations, how a suitably concentrated solution formed by the partial neutralization of 2,2-dimethylpropanoic acid with sodium hydroxide acts as a buffer solution. [2]

4. Titration of 10.00 mL of an Acid with 0.150 mol/L Strong Base

a. This is a (strong/weak) acid titrated with a strong base. The acid is ( monoprotic /diprotic). [2] b. How would the other strength of acid look? (sketch it on the graph) (Strong or weak) [1] c. Place a dot (.) on the curve at the equivalence point. The pH at the equivalence point is ____. Choose a good indicator for this titration [2] d. Write the indicator reaction that takes place at the equivalence point. What would the colour change be?

[2] e. Label the buffering region on the pH curve. [1] f. Why is the pH at the equivalence point >7? [2]

g. The volume of strong base required to reach the equivalence point is ___ mL.

[1]

h. Calculate the concentration of the acid. [2]

i.

Use your answer from question h and the initial pH of the acid (read from the graph) to calculate the Ka of the acid. [2]

j. Sketch the titration curve that would result from the titration of 10.00 mL of of 1.00 mol/L NH3(aq) by adding 0.500 mol/L HCl(aq). Label the equivalence point. [4]

5. Complete the following reactions, and write the net ionic equations: a. Na2SO3 (aq) + 2HCl(aq) [2]

b. HC6H5CO2 (aq) + NaOH (aq) [2]