Question

(a) Valeric acid (CH₂(CH₂)3COOH) is described as a weak acid.

Define the term weak acid.
Weak Acids are acids that partially release hydrogen atoms and
lower pH due to disassociation resulting in the formation of a weak
acid.
(b) Write a balanced chemical equation to show the dissociation of
Valeric acid (CH3(CH₂)3COOH). Physical states must be included
CH₂(CH₂)3COOH
(c) When Valeric acid (CH₂(CH₂)3COOH) reacts with the strong base
sodium hydroxide (NaOH), sodium valerate (CH3(CH₂)3COONa), a
salt of the weak acid is formed.
Write a balanced chemical equation to show the dissociation of the
sodium valerate (CH₂(CH₂)3COONa). Physical states must be
included.
CH₂(CH₂)3COONa)
(d) A solution of a weak acid and the salt of that weak acid can
behave as a buffer solution. Describe the term buffer solution. No
chemical equations are needed.
Buffer solutions are solutions that resist change and maintain pH
of a solution.
(e) Explain how solution of valeric acid and sodium valerate can
function as a buffer solution.
Your answer must include a brief description on how this buffer
functions on the addition of; (i) a small amount of acid (1 mark), (ii)
a small amount of alkali (1 mark), (iii) a small amount of distilled
water (1 mark) and (iv) include balanced chemical equations,
physical states included (1 mark).
(1)
All sources need to be acknowledged using Harvard referencing
(2 Marks)
(2 Marks)
(2 Marks)
(2 Marks)
(4 Marks)
(4 Morld
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Answer 1

(a) A weak acid is an acid that partially dissociates in water, releasing a small amount of hydrogen ions (H+) and resulting in a pH lower than 7.

(b) The balanced chemical equation for the dissociation of valeric acid is:

CH3(CH2)3COOH (aq) ⇌ CH3(CH2)3COO- (aq) + H+ (aq)

(aq) denotes that the compound is dissolved in water.

(c) The balanced chemical equation for the dissociation of sodium valerate is:

CH3(CH2)3COONa (aq) ⇌ CH3(CH2)3COO- (aq) + Na+ (aq)

(d) A buffer solution is a solution that can resist changes in pH when small amounts of acid or base are added to it. Buffer solutions contain a weak acid and its conjugate base or a weak base and its conjugate acid. The weak acid or base can neutralize any added acid or base, maintaining a stable pH.

(e) A solution of valeric acid and sodium valerate can function as a buffer solution because valeric acid is a weak acid and sodium valerate is its conjugate base. When small amounts of acid are added to the buffer solution, the valeric acid can neutralize it by accepting hydrogen ions, while the sodium valerate can neutralize small amounts of base by releasing hydrogen ions. Additionally, the buffer solution resists changes in pH when small amounts of distilled water are added because the valeric acid and sodium valerate concentrations remain relatively constant. The balanced chemical equations for these reactions are:

(i) Valeric acid + H+ ⇌ CH3(CH2)3COOH2+

(ii) Sodium valerate + OH- ⇌ CH3(CH2)3COOH + NaOH

(iii) CH3(CH2)3COOH ⇌ CH3(CH2)3COO- + H+

(iv) CH3(CH2)3COO- + H+ ⇌ CH3(CH2)3COOH