EmSAT EmSAT Chemistry 5 — Questions and Answers
Question 1: What is the pH of a strong acid with [H⁺] = 0.01 M?
- 1
- 2 (Correct answer)
- 3
- 4
Correct answer: 2
pH = −log[H⁺] = −log(0.01) = −log(10⁻²) = 2.
Question 2: What happens when a weak acid dissolves in water?
- It fully ionizes
- It partially ionizes, reaching equilibrium (Correct answer)
- It does not react with water
- It forms a precipitate
Correct answer: It partially ionizes, reaching equilibrium
Weak acids only partially ionize in water, establishing an equilibrium between the ionized and non-ionized forms. This contrasts with strong acids, which fully dissociate.
Question 3: What is a buffer solution?
- A solution with pH = 7
- A solution that resists changes in pH when small amounts of acid or base are added (Correct answer)
- A strong acid solution
- A solution with no ions
Correct answer: A solution that resists changes in pH when small amounts of acid or base are added
A buffer solution resists significant changes in pH when small amounts of acid or base are added. Buffers typically consist of a weak acid and its conjugate base (or vice versa).
Question 4: In a titration, what is the equivalence point?
- When the indicator changes color
- When the pH equals 7
- When moles of acid equal moles of base (Correct answer)
- When the solution turns red
Correct answer: When moles of acid equal moles of base
The equivalence point in a titration is the point at which the moles of acid are exactly equal to the moles of base — they have completely neutralized each other.
Question 5: What is the conjugate base of H₂CO₃?
- H₃O⁺
- CO₃²⁻
- HCO₃⁻ (Correct answer)
- OH⁻
Correct answer: HCO₃⁻
When H₂CO₃ donates a proton (H⁺), it becomes HCO₃⁻ (bicarbonate ion), its conjugate base. Conjugate base = acid − one proton.
Question 6: What type of reaction is HCl + NaOH → NaCl + H₂O?
- Combustion
- Neutralization (Correct answer)
- Decomposition
- Precipitation
Correct answer: Neutralization
The reaction between an acid (HCl) and a base (NaOH) producing a salt (NaCl) and water (H₂O) is a neutralization reaction.
EmSAT EmSAT Chemistry 5
What is the pH of a strong acid with [H⁺] = 0.01 M?