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1. New substances are formed. 2. The change is often irreversible.

(a) (ii)

Answer: Iron + Oxygen → Iron oxide

(b) (i)

1. Alkalis contain hydroxide ions.

2. The formula for the hydroxide ion is OH⁻.

Answer: Name: Hydroxide ion; Formula: OH⁻

(b) (ii)

1. Test: Bubble the gas through limewater (calcium hydroxide solution)

2. Observation: The limewater will turn milky or cloudy if carbon dioxide is present.

Answer: Test: Bubble the gas through limewater. Observation: Limewater turns milky/cloudy.

(b) (iii)

Answer: Litmus

(b) (iv)

1. Carefully add a few drops of a suitable indicator (e.g., litmus) to separate samples of the acid and alkali.

2. Observe the color change. Litmus turns red in acid and blue in alkali. Alternatively, a universal indicator could be used to determine the pH.

Answer: Add a few drops of litmus solution to separate samples. Acid will turn litmus red, and alkali will turn litmus blue.

(a) (i)

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Zn + 2HCL-> ZnCl2 +H2

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NaOH(aq) + HNO3 (aq) -> NaNO3 (aq) + H2O (l)

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CaCO3(l) + H2SO4 (aq) -> CaSO4 (l) + CO2 (g) +H2O (l)

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1a. 2NaOH (aq) + H2SO4 (aq) -> Na2SO4 (aq) + 2 H2O (l)

2a. CaCl2 (aq) + 2AgNO3 (aq) -> 2AgCl (s) + Ca(NO3)2 (aq)