Question detail

Chemical changes case 153 reactivity-evidence. A student uses the reactivity series to justify an observation. Which option is best? Focus on why increases when acid neutralised alkali in The pH scale and neutralisation, not on a neighbouring Unit 4.4 reaction idea.

Try the question, check the answer, then read the explanation to understand the curriculum point.

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At a glance

MCQ

Type

practice

Style

Topic

Reactions of acids

Question

A. Chemical changes case 153 reactivity-evidence: Uses the relative reactivity order to predict the change for why increases when acid neutralised alkali
B. Chemical changes case 153 reactivity-evidence: Chooses the product by memorising a colour instead of the series (The pH scale and neutralisation)
C. Chemical changes case 153 reactivity-evidence: Says any metal can displace any other metal ion (why increases when acid neutralised alkali)
D. Chemical changes case 153 reactivity-evidence: Ignores whether the reacting substance is more or less reactive (Reactions of acids)

Answer

The correct option is Chemical changes case 153 reactivity-evidence: Uses the relative reactivity order to predict the change for why increases when acid neutralised alkali.

Explanation

The correct option is Chemical changes case 153 reactivity-evidence: Uses the relative reactivity order to predict the change for why increases when acid neutralised alkali. It is correct because it directly supports the approved learning objective to explain why pH increases when an acid is neutralised by an alkali in The pH scale and neutralisation. The other options are incorrect because they blur a Unit 4.4 concept boundary: acid versus alkali versus base, oxidation versus reduction, displacement versus reduction, electrolysis versus electroplating, anode versus cathode, positive versus negative ions, oxidation state versus ionic charge, or strong acid versus concentrated acid.

Common mistake

Misinterpreting pH change as a direct ion count

Students often think that because neutralisation removes H⁺ ions, the pH simply jumps to a fixed value, ignoring the logarithmic scale and concentration of OH⁻ added.

Explain that pH is calculated from the negative log of the H⁺ concentration; when an alkali supplies OH⁻, the H⁺ concentration falls exponentially, so the pH rises by a number of units that depends on the amount of OH⁻ added and the initial H⁺ concentration, not by a fixed amount.

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For The pH scale and neutralisation, which electrolysis focus answer best supports this Unit 4.4 objective: Explain why pH increases when an acid is neutralised by an alkali?