Question

Consider a solution which is 0.10M in CH3COOH and 0.20M in NaCH3COO. Choose ALL of the following that are true. If Ca(CH3COO)2 is added, the pH becomes more basic. If a small amount of HCl is added, the pH becomes slightly more acidic. If HCl is added, the H ions react with the CH3COOH. If a small amount of NaOH is added, the pH becomes slightly more acidic. If NaOH is added, the OH- ions react with the CH3COO- ions.

Answer 1

Answer:

The first 2 statements are correct. The others are false.

If Ca(CH3COO)2 is added, the pH becomes more basic.

If a small amount of HCl is added, the pH becomes slightly more acidic.

Explanation:

Step 1: Data given

Molarity of a CH3COOH solution = 0.10 M

⇒CH3COOH is a weak acid

Molarity of a NaCH3COO solution = 0.20 M

Step 2: If Ca(CH3COO)2 is added, the pH becomes more basic.

Ca(CH3COO)2 → Ca^2+ + 2CH3COO-

This means when we add Ca(CH3COO)2, the amount of CH3COO- will be increased.

CH3COO- is the conjugate base of the acid CH3COOH.

By increasing the amount of the conjugate base CH3COO- the pH will become more basic.

The first statement is true.

Step 3:  If a small amount of HCl is added, the pH becomes slightly more acidic

This is true. By adding a strong acid, the pH will become more acid.

Step 4: If HCl is added, the H ions react with the CH3COOH.

When the strong acid HCl is added. The H+ ions will react with a negative charged compound. This will not be CH3COOH but it's conjugate base CH3COO-

This statement will be false.

Step 5:  If a small amount of NaOH is added, the pH becomes slightly more acidic.

When we add HCl, ste pH will become more acid. NaOH is a strong base. When adding a strong base, the pH will become (slightly) more basic, not more acid.

This statement is false.

Step 6: If NaOH is added, the OH- ions react with the CH3COO- ions.

The OH- ions of NaOH are negative charged, they will not react with the CH3COO- ions because those are also negative charged.

This statement is false?

The first 2 statements are correct. The others are false.

If Ca(CH3COO)2 is added, the pH becomes more basic.

If a small amount of HCl is added, the pH becomes slightly more acidic.

Answer 2

Answer:

If Ca(CH₃COO)₂ is added, the pH becomes more basic.

If a small amount of HCl is added, the pH becomes slightly more acidic.

Explanation:

In the buffer:

CH₃COOH (weak acid) and NaCH₃COO (conjugate base), the equilibrium in water is:

CH₃COOH ⇄ CH₃COO⁻ + H⁺

CH₃COOH will react if a base is added and CH₃COO⁻ reacts if an acid is added decreasing the pH change. Thus:

If Ca(CH₃COO)₂ is added, the pH becomes more basic. TRUE. Here, you are adding CH₃COO⁻ (Conjugate base), as a base, pH will decreases.

If a small amount of HCl is added, the pH becomes slightly more acidic. TRUE. As buffer, the addition of strong acids as HCl decrese slightly the pH of the solution.

If HCl is added, the H ions react with the CH₃COOH. FALSE. The strong acid reacts with the conjugate base, CH₃COO⁻

If a small amount of NaOH is added, the pH becomes slightly more acidic. FALSE. The addition of a strong base as NaOH become pH slightly more basic.

If NaOH is added, the OH⁻ ions react with the CH₃COO⁻ ions. FALSE. A strong acid reacts with the weak acid, CH₃COOH.