Acids bases and buffers (proton transfer reactions DP Chemistry)

Chloric(I) acid, HClO, and nitric(III) acid, HNO₂, form the equilibrium

HClO + HNO₃ ⇌ H₂ClO⁺ + NO₂^-

A Brønsted-Lowry acid and its conjugate base are

• A

• B

• C

• D

A buffer solution is 0.1 mol dm⁻³ with respect to ethanoic acid and 0.05 mol dm⁻³ with respect to sodium ethanoate.

K_a for ethanoic acid = 1.7 × 10⁻⁵ mol dm⁻³

The pH of this buffer solution is?

• 2.88

• 4.47

• 4.77

• 5.07

When a small amount of hydrochloric acid is added to a buffer solution, the change in pH is very small.

What is the best explanation for this?

• The dissociation of the acid in the buffer solution is small.

• The concentration of the buffer solution only changes a little

• The ratio of the concentration of acid to conjugate base in the buffer solution does not change.

• The ratio of the concentration of acid to conjugate base in the buffer solution only changes a little.

Calculate the pH of an aqueous solution of hydrochloric acid, HCl, of concentration 0.40 mol dm^–3

• 0.40

• -0.40

• -0.92

• 0.92

Which solution has the highest pH?

• 0.010 mol dm^–3 sodium hydroxide solution

• 0.100 mol dm^–3 sodium hydroxide solution

• 0.010 mol dm^–3 aqueous ammonia

• 0.100 mol dm^–3 aqueous ammonia

A solution containing HCN and KCN is a buffer. When a small amount of acid is added, the solution acts as a buffer because

• hydrogen ions in the acid combine with cyanide ions to make HCN.

• hydrogen ions in the acid combine with HCN to make H₂CN⁺.

• HCN dissociates to make more CN^– ions.

• the hydrogen ions in the acid prevent dissociation of the HCN.

At 18 °C, the ionic product of water, K_w, is 6.4 × 10^–15 mol² dm^–6.

At this temperature, water is

• neutral with a pH of 7.0

• neutral with a pH of 7.1

• alkaline with a pH of 7.1

• alkaline with a pH of 7.2

The equation for the reaction between a weak acid, HX, and sodium hydroxide is

HX(aq) + NaOH(aq) → NaX(aq) + H₂O(l)

The pH of the solution of the salt NaX is most likely to be

• 5.5

• 7.0

• 8.5

• 13.0

The pH of three solutions with concentration 1.0 mol dm^–3 was measured.

Solution 1    NH₃

Solution 2    CH₃COONa

Solution 3    NH₄Cl

Which of the following shows the three solutions in order of increasing pH?

NH₄⁺ K_a=5.6 x 10^-10

CH₃COOH K_a= 1.7 x 10^-5

• 1,2,3

• 3,2,1

• 3,1,2

• 2,3,1

The titration curves shown were obtained using different acids and bases, each with a concentration of 0.1 mol dm^-3.

Which curve shows the pH change when nitric acid is added to 25 cm³ of sodium hydroxide?

• 
• 
• 
•