Question

chapter 10: skill - builder
due sunday by 11:59pm
points 10
submitting an external tool
fill in the missing words
a) in an hf - kf buffer hydrofluoric acid is a(n) component in the buffer and fluoride is a(n) component. when a small amount of hcl is added to the buffer, reacts with hydronium ions produced by hcl. when a small amount of naoh is added to the buffer, reacts with hydroxide ions produced by naoh. in both cases the of the solution does not change, or changes very little.
b) in an $nh_3 - nh_4^+$ buffer ammonium is a(n) component in the buffer and ammonia is a(n) component. when a small amount of hcl is added to the buffer, reacts with hydronium ions produced by hcl. when a small amount of naoh is added to the buffer, reacts with hydroxide ions produced by naoh. in both cases the of the solution does not change, or changes very little.

Explanation:

Part (a) - HF - KF Buffer

• A buffer consists of a weak acid and its conjugate base (or a weak base and its conjugate acid). Hydrofluoric acid (HF) is a weak acid, so it is the acidic component of the HF - KF buffer.
• Fluoride ion (from KF, \(F^-\)) is the conjugate base of HF, so fluoride is the basic component.
• When HCl (a strong acid, providing \(H_3O^+\)) is added to the buffer, the basic component (\(F^-\)) reacts with \(H_3O^+\) (hydronium ions) to form HF: \(F^-+H_3O^+

ightleftharpoons HF + H_2O\).

• When NaOH (a strong base, providing \(OH^-\)) is added to the buffer, the acidic component (HF) reacts with \(OH^-\) (hydroxide ions) to form \(F^-\) and \(H_2O\): \(HF + OH^-

ightleftharpoons F^-+H_2O\). In both cases, the \(pH\) (or the hydronium ion concentration) of the solution changes very little.

Filling the Blanks:

• In an HF - KF buffer, hydrofluoric acid is a(n) \(\boldsymbol{\text{acidic}}\) component in the buffer and fluoride is a(n) \(\boldsymbol{\text{basic}}\) component. When a small amount of HCl is added to the buffer, \(\boldsymbol{F^-}\) reacts with hydronium ions produced by HCl. When a small amount of NaOH is added to the buffer, \(\boldsymbol{HF}\) reacts with hydroxide ions produced by NaOH. In both cases, the \(\boldsymbol{pH}\) of the solution does not change, or changes very little.

Part (b) - \(NH_3 - NH_4^+\) Buffer

• Ammonium ion (\(NH_4^+\)) is the conjugate acid of ammonia (\(NH_3\)), so \(NH_4^+\) is the acidic component of the \(NH_3 - NH_4^+\) buffer.
• Ammonia (\(NH_3\)) is a weak base, so it is the basic component.
• When HCl (providing \(H_3O^+\)) is added to the buffer, the basic component (\(NH_3\)) reacts with \(H_3O^+\) to form \(NH_4^+\): \(NH_3 + H_3O^+

ightleftharpoons NH_4^++H_2O\).

• When NaOH (providing \(OH^-\)) is added to the buffer, the acidic component (\(NH_4^+\)) reacts with \(OH^-\) to form \(NH_3\) and \(H_2O\): \(NH_4^++OH^-

ightleftharpoons NH_3 + H_2O\). In both cases, the \(pH\) (or the hydronium ion concentration) of the solution changes very little.

Filling the Blanks:

• In an \(NH_3 - NH_4^+\) buffer, ammonium is a(n) \(\boldsymbol{\text{acidic}}\) component in the buffer and ammonia is a(n) \(\boldsymbol{\text{basic}}\) component. When a small amount of HCl is added to the buffer, \(\boldsymbol{NH_3}\) reacts with hydronium ions produced by HCl. When a small amount of NaOH is added to the buffer, \(\boldsymbol{NH_4^+}\) reacts with hydroxide ions produced by NaOH. In both cases, the \(\boldsymbol{pH}\) of the solution does not change, or changes very little.

Final Answers (Filled Blanks)

Part (a)

• acidic; basic; \(F^-\); HF; \(pH\)

Part (b)

• acidic; basic; \(NH_3\); \(NH_4^+\); \(pH\)

Answer:

• Ammonium ion (\(NH_4^+\)) is the conjugate acid of ammonia (\(NH_3\)), so \(NH_4^+\) is the acidic component of the \(NH_3 - NH_4^+\) buffer.
• Ammonia (\(NH_3\)) is a weak base, so it is the basic component.
• When HCl (providing \(H_3O^+\)) is added to the buffer, the basic component (\(NH_3\)) reacts with \(H_3O^+\) to form \(NH_4^+\): \(NH_3 + H_3O^+

ightleftharpoons NH_4^++H_2O\).

• When NaOH (providing \(OH^-\)) is added to the buffer, the acidic component (\(NH_4^+\)) reacts with \(OH^-\) to form \(NH_3\) and \(H_2O\): \(NH_4^++OH^-

ightleftharpoons NH_3 + H_2O\). In both cases, the \(pH\) (or the hydronium ion concentration) of the solution changes very little.

Filling the Blanks:

• In an \(NH_3 - NH_4^+\) buffer, ammonium is a(n) \(\boldsymbol{\text{acidic}}\) component in the buffer and ammonia is a(n) \(\boldsymbol{\text{basic}}\) component. When a small amount of HCl is added to the buffer, \(\boldsymbol{NH_3}\) reacts with hydronium ions produced by HCl. When a small amount of NaOH is added to the buffer, \(\boldsymbol{NH_4^+}\) reacts with hydroxide ions produced by NaOH. In both cases, the \(\boldsymbol{pH}\) of the solution does not change, or changes very little.

Final Answers (Filled Blanks)

Part (a)

• acidic; basic; \(F^-\); HF; \(pH\)

Part (b)

• acidic; basic; \(NH_3\); \(NH_4^+\); \(pH\)