Science — AI-generated practice question

(a) Bulb glows with dilute HCl and dilute NaOH only.

Dilute HCl produces H⁺(aq) and Cl⁻ ions in solution, while dilute NaOH produces Na⁺(aq) and OH⁻(aq) ions. These free ions carry electric current through the solution, completing the circuit and making the bulb glow.

Glucose and alcohol solutions do not ionise in water — they contain no free ions — so they do not conduct electricity and the bulb does not glow.

(b) This experiment proves that acids produce H⁺(aq) ions and bases produce OH⁻(aq) ions in aqueous solution. These ions are responsible for electrical conductivity and hence for the acidic and basic properties respectively. Compounds like glucose and alcohol, though they contain hydrogen, do not ionise and are therefore not acidic.

(c) Distilled water is pure and contains no dissolved ions, so it cannot conduct electricity. Rainwater dissolves CO₂ from the atmosphere to form carbonic acid (H₂CO₃), which ionises to give H⁺ and HCO₃⁻ ions. These ions make rainwater a conductor.

Source: Chapter 2, Section 2.2

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• The key examiner expectation is ions = conductivity: always link glowing bulb → ions present → current flows.
• For part (b), name both ions explicitly: H⁺(aq) for acids, OH⁻(aq) for bases.
• For part (c), the contrast is no ions (distilled) vs. ions from dissolved CO₂ (rainwater) — both points needed for full credit.
• Glucose/alcohol: stress they contain hydrogen but do not ionise — this directly answers the textbook's investigative question in Activity 2.8.