# Worksheet: Concentrations from Ionization Constants

In this worksheet, we will practice using dissociation constants to find the equilibrium concentrations of undissociated acids and bases.

Q1:

Acetic acid is the principal ingredient in vinegar. In a sample of vinegar at equilibrium, and . What is the value of for acetic acid?

• A
• B
• C
• D
• E

Q2:

What is the hydronium ion concentration in a 0.100 M solution of ammonium nitrate, , a salt composed of the ions and ? of ammonia is .

• A M
• B M
• C M
• D M
• E M

Q3:

Caffeine, , is a weak base. What is the value of for caffeine if a solution at equilibrium has , , and ?

• A
• B
• C
• D

Q4:

Consider the equilibrium for the ionization of trimethylamine, a weak base.

The of trimethylamine is . Assuming the effect of dissociation on the trimethylamine concentration is negligible, calculate the concentration of hydroxide ions in a 0.25 M trimethylamine solution.

• A M
• B M
• C M
• D M
• E M

Q5:

Consider the following equilibrium.

What is the equilibrium acetic acid concentration in a solution where and at equilibrium? The of acetic acid is .

• A M
• B M
• C M
• D M
• E M

Q6:

When dissolves in water, ions are formed. The ion acts as a monoprotic acid with a value of . Calculate the concentration of ions in a 0.15 M solution of if the concentration of ions is 0.10 M.

• A M
• B M
• C M
• D M
• E M

Q7:

When dealing with acid and base solutions, when is it necessary to use equilibrium calculations to accurately determine equilibrium concentrations?

• AIn nonaqueous systems
• BWhen the temperature is not
• COnly at very low concentrations
• DWhen a strong acid or base is involved
• EWhen a weak acid or base is involved

Q8:

In an aqueous solution at equilibrium, , and . Calculate the value of for .

• A
• B
• C
• D
• E1.07

Q9:

In a hypochlorous acid solution at equilibrium, , and . Calculate to 3 significant figures the value of for .

• A
• B
• C
• D
• E

Q10:

In a solution of acetic acid at equilibrium, , , and . What is the value of for ?

• A
• B
• C
• D
• E

Q11:

Using the equilibrium concentrations and what is the value of for ?

• A
• B
• C
• D0.10
• E

Q12:

Using the equilibrium concentrations ,

,

and ,

what is the value of for ?

• A
• B
• C
• D
• E

Q13:

For which of the following solutions must we consider the ionization of water when calculating the pH or pOH?

• A2 M
• B0.00080 g   in 0.10 L of solution
• C M
• D M
• E0.10 g   in 1.0 L of solution

Q14:

A 0.134 M solution of the diprotic acid contains , , , , and . Which two of these species are present in almost equal concentrations?

• A and
• B and
• C and
• D and
• E and

Q15:

What is the concentration of in a 0.0092 M aqueous solution of hypochlorous acid at ? The of hypochlorous acid is .

• A0.0092 M
• B M
• C M
• D M
• E M

Q16:

What is the concentration of in 0.120 M at ? of is .

• A M
• B M
• C M
• D M
• E M

Q17:

What is the concentration of in 0.0810 M at ? of is .

• A M
• B M
• C M
• D0.081 M
• E M

Q18:

What is the concentration of in 0.0784 M at ? of is .

• A0.078 M
• B M
• C M
• D M
• E M

Q19:

What is the concentration of in 0.11 M at ? of is .

• A M
• B M
• C M
• D M
• E M

Q20:

In a trimethylamine solution at equilibrium, , , and . Calculate the value of for trimethylamine.

• A
• B
• C0.29
• D
• E

Q21:

Propionic acid, () is used in the manufacture of calcium propionate, a food preservative. Calculate to 2 significant figures the hydronium ion concentration in a 0.712 M solution of .

• A M
• B M
• C M
• D M
• E M

Q22:

The ionization constant of lactic acid, , an acid found in blood after strenuous exercise, is . If 15.0 g of lactic acid is used to make a solution with a volume of 1.00 L, what is the concentration of hydronium ions in the solution?

• A M
• B M
• C M
• D M
• E M

Q23:

A 1.00 L stock solution is prepared by dissolving 1.00 mole of a monoprotic acid in water. The value of the acid is 0.050. When calculating at equilibrium, a student assumes that the change in concentration of the undissociated acid is negligible. Calculate to 2 significant figures the percentage error in the calculated value of relative to the true value.