Strong/weak acids -Grade Gorilla IB Chemistry

10 minutes maximum

An IB Periodic Table is required.

1. Choose the correct description from the following statements:

A. Normal rain water has a pH of 7.
B. Acid deposition is formed when oxides of carbon dissolve in water.
C. Reacting with calcium carbonate is a post-combustion method for reducing sulphur dioxide emissions.
D. Acid rain has a pH above 5.6.

ABCD

2. Which of the solutions below has the highest pH when measured at equimolar concentrations?

A. HCOOH
B. HCl
C. NH₃
D. NH₄Cl

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3. Which of the following statements is true?

A. A strong acid always has a lower pH than a weak acid.
B. A strong acid is always more concentrated than a weak acid.
C. A stronger acid has a weaker conjugate base.
D. A stronger acid conducts electricity better than a weaker acid.

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4. Which of the acids below has the weakest conjugate base?

A. Hydrochloric acid
B. Propanoic acid
C. Carbonic acid
D. Sulfurous acid

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5. There are equimolar solutions of sulphuric acid, hydrochloric acid, ethanoic acid and carbonic acid. Which solution has the lowest pH when measured with a pH meter?

A. Sulphuric acid
B. Hydrochloric acid
C. Ethanoic acid
D. Carbonic acid

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6. Which of the following solutions has the lowest conductivity?

A. 1 mol dm^-3 HNO₃ (aq)
B. 1 mol dm^-3 NaOH (aq)
C. 1 mol dm^-3 NH₃ (aq)
D. 1 mol dm^-3 NH₄Cl (aq)

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7. Which two oxides form solutions of pH<7 when added to water?

A. SiO₂ and SO₂
B. MgO and Al₂O₃
C. Na₂O and MgO
D. P₄O₁₀ and SO₃

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8. Complete the following sentences:

A 0.1 mol dm^-3 solution of an acid HA has a pH of 2.9. HA is a acid.

9. Ethanoic acid is a weak acid:

CH₃COOH + H₂O ⇌ CH₃COO^- + H₃O⁺

Which of the following statements about the aqueous solution of ethanoic acid is correct?

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A. CH₃COOH is a stronger acid than H₃O⁺.
B. H₂O is a weaker base than CH3COO^-.
C. CH₃COOH dissociates completely in water.
D. The concentration of CH₃COO^- is higher than the concentration of CH₃COOH.

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10. Equal concentrations of a strong acid and a weak acid, both monoprotic, can be distinguished using some of the following methods. Which ones are correct?

I. Measuring the pH of the acids using a pH meter and a data logger

II. Measuring the rate of bubbling when magnesium powder is added into each solution

III. Measuring the volume of sodium hydroxide required for changing the colour of the phenolphthalein indicator, during titration of the acids.

A. I and II only
B. I and III only
C. II and III only
D. I, II and III

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