1) A What is the pH after 0.150 mol of HCl is added to the buffer from Part A? A

ID: 1047635 • Letter: 1

Question

What is the pH after 0.150 mol of HCl is added to the buffer from Part A? Assume no volume change on the addition of the acid.

Express the pH numerically to three decimal places.

What is the pH after 0.195 mol of NaOH is added to the buffer from Part A? Assume no volume change on the addition of the base.

Express the pH numerically to three decimal places.

Calculate the ratio of CH3NH2 to CH3NH3Cl required to create a buffer with pH = 10.20.

Express your answer using two significant figures.

3) Ammonia, NH3, is a weak base with a Kb value of 1.8×105.

Part A

What is the pH of a 8.00×102M ammonia solution?

Express your answer numerically to two decimal places.

Part B

What is the percent ionization of ammonia at this concentration?

Express your answer with the appropriate units.

If Kb for NX3 is 8.5×106 , what is the the pKa for the following reaction?

HNX3+(aq)+H2O(l)NX3(aq)+H3O+(aq)

Express your answer numerically to two decimal places.

PART A

pH of NH3 solution

Kb = 1.8*10^-5

NH3 + H2O <-> NH4+ + OH-

Kb = [NH4+][[OH-]/[NH3]

1.8*10^-5 = x*x /(8*10^-2x)

x = 0.00119

x = [OH-] = 0.00119

pOH = -log(0.00119) = 2.9244

pH = 14-2.9244 = 11.0756

PART B)

% ionization = [OH-]/M* 100% = 0.00119/ (8*10^-2) *100 = 1.4875 %

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