Question 1

Write each answer with the correct number of digits:

a) 3.021 + 8.99 =

d) 0.0302 ÷ (2.1143 × 10^-3) =

b) 12.7 - 1.83 =

e) log (2.2 × 10^-18) =

g) 10^-4.555 =

c) 6.345 × 2.2 =

f) antilog (-2.224) =

Question 2

Find the absolute and percent relative uncertainty and express each answer with a reasonable number of significant figures:

a) 3.4 (±0.2) + 2.6 (±0.1) =

b) [3.4 (±0.2) × 10-8] ÷ [2.6 (±0.1) × 103] =

c) 3.4 (±0.2) ÷ 2.6 (±0.1) =

d) [3.4 (±0.2) - 2.6 (±0.1)] × 3.4 (±0.2) =

Question 3

a) A solution is prepared by dissolving 0.2222 (±0.0002) g of KIO₃ [FM 214.0010 ±0.0009] in 50.00 (±0.05) mL. Find the molarity and its uncertainty with an appropriate number of significant figures.

b) Would the answer be affected significantly if the reagent were only 99.9% pure?

Question 4

Using activity coefficients correctly, calculate the pH of

a) 0.050 M HBr

b) 0.050 M NaOH

Question 5

Find the pH and fraction of dissociation (α) of a 0.010 0 M solution of the weak acid HA with

K_a = 1.00 × 10^-4.

Question 6

A 0.100 M solution of the weak acid HA has a pH of 2.36. Calculate pKa for HA.

Question 7

Calculate the concentration of Tl⁺ in a saturated solution of TlBr in water (K_sp = 3.7 x 10^-9). Include activity effects.

a) Calculate the concentration of Tl⁺ in a saturated solution of TlBr in 0.9 % w/v NaCl solution. Include activity effects.

b) Comment on the difference between you answers to a) and b) above.

Questions 8:

a. Why do we worry about significant figures?

b. What do we mean by the term 'ionic strength' and 'activity'? What are these things important? What are the implications for solutions?

c. What happens to the amount of ionisation as we increase the ionic strength of a solution? What happens to the solubility of a salt?

d. What is meant by the various terms we use when discussing analytical techniques?