Zoom SI 04.14.23

Which one of the following is the weakest acid?

• HF (Ka=6.8×10^-4)

• HCN (Ka=4.9×10^-10)

• HClO (Ka=3.0×10^-8)

• Acetic acid (Ka=1.8×10^-5)

• HNO2 (Ka=4.5×10^-4)

Using the data in the table, which of the conjugate acids below is the weakest acid?

• NH3CH3+

• H2S

• HClO

• HCO3-

HZ is a weak acid. An aqueous solution of HZ is prepared by dissolving 0.020 mol of HZ in sufficient water to yield 1.0 L of solution. The pH of the solution was 4.93 at 25.0°C. The Ka of HZ is ________.

• 1.2×10^-5

• 9.9×10^-2

• 6.9×10^-9

• 2.8×10^-12

• 1.4×10^-10

Of the following solutions, which has the greatest buffering capacity?

• 0.121 M HC2H3O2 and 0.116 M NaC2H3O2

• 0.821 M HC2H3O2 and 0.713 M NaC2H3O2

• 0.365M HC2H3O2 and 0.497 M NaC2H3O2

• 0.521 M HC2H3O2 and 0.217 M NaC2H3O2

A 25.0 mL sample of a solution of an unknown compound is titrated with a 0.115 M NaOH solution. This titration curve was obtained. The unknown compound is ________.

• a strong base

• a strong acid

• a weak acid

• a weak base

Calculate the percent ionization of formic acid (HCO2H) in a solution that is 0.322M in formic acid and 0.178M in sodium formate (NaHCO2). The Ka of formic acid is 1.77×10^-4.

• 3.488

• 0.00103

• 35.6

• 0.1011

• 10.8

Calculate the percent ionization of nitrous acid in a solution that is 0.260 M in nitrous acid. The acid dissociation constant of nitrous acid is 4.50×10^-4.

• 0.0450

• 4.16

• 5.78

• 0.314

• 0.000117

What is the pH of a buffer solution that is 0.266 M in lactic acid and 0.111 M in sodium lactate? The Ka of lactic acid is 1.4×10^-4.

• 5.38

• 10.53

• 4.23

• 14.38

• 3.47

Consider a solution containing 0.100 M fluoride ions and 0.126 M hydrogen fluoride. The concentration of fluoride ions after the addition of 9.00 mL of 0.0100 M HCl to 25.0 mL of this solution is ________ M.

• 0.00253

• 0.0980

• 0.0762

• 0.0735

• 0.0709