Unit 10 Review

Which 0.1 M aqueous solution is the best conductor of electricity?

• H₂SO₄

• H₃PO₄

• HNO₂

• HF

Answer explanation

H₂SO₄ is the only strong acid of the 4 listed.

What is the pH of a 0.01 M solution of KOH?

Answer explanation

pOH = - log[OH^-1] and pH = 14 - pOH

- log [0.01] = 2 so 14 - 2 = 12

What are the relative ion concentrations in an acid solution?

• More H⁺ ions than OH^- ions

• H⁺ ions but no OH^- ions

• An equal number of H⁺ ions and OH^- ions

• Fewer H⁺ ions than OH^- ions

Answer explanation

Since it is an acidic solution there will be more H⁺¹ ions than OH^-1 ions.

The equation below represents the equilibrium state of aqueous phosphoric acid.

H₃PO₄(aq) ↔ H⁺¹(aq) + H₂PO₄^-1(aq)

Which of the following is equal to the ionization constant K_a?

• Products / Reactants

• Reactants / Products

What is the pH of a 0.10 M solution of NaOH?

Answer explanation

pOH = - log[OH^-1] and pH = 14 - pOH

- log [0.1] = 1 so 14 - 1 = 13

What is the conjugate base of H₂PO₄^-1?

• H₃PO₄

• HPO₄^-2

• H⁺¹

• PO₄^-3

Answer explanation

The conjugate base has one less H than the original species.

Which of the following is the weakest acid?

• HI

• HF

• H₂SO₄

• HNO₃

Answer explanation

HF is the only weak acid of the 4 listed.

A chemist prepared a solution of NaOH by completely dissolving 55.90 grams of solid NaOH in 3.600 liters of water at room temperature. What was the pH of the solution that the chemist prepared?

Answer explanation

55.90 g NaOH / 40.0 g mol^-1 NaOH = 1.398 mol NaOH

1.398 mol NaOH / 3.600 L = 0.3882 M NaOH

pOH = - log [0.3882] = 0.4109

pH = 14 - 0.4109 = 13.59

The conjugate acid of the HS^-1 ion is —

• H⁺¹

• H₂O

• H₂S

• S

Answer explanation

The conjugate acid will have one more H than the original species.

At 1 atm and 298 K, which of the K_a values listed below represents the strongest acid?

• 5.6 x 10^-11

• 4.6 x 10^-4

• 1.1 x 10^-7

• 1.8 x 10^-5

Answer explanation

An acid with a larger K_a value dissociates more (adds more H⁺¹ into solution). Although 4.6 x 10^-4 is a small number, it is the the largest of the 4 choices.