Question detail
Chemical changes case 106 electrode-ions. A student predicts electrolysis products. Which option keeps ions and electrodes clear? Focus on that lower means higher hydrogen ion concentration in Strong and weak acids (HT only), not on a neighbouring Unit 4.4 reaction idea.
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Reactions of acids
Question
- A. Chemical changes case 106 electrode-ions: Matches the ion movement to the correct electrode and product for that lower means higher hydrogen ion concentration
- B. Chemical changes case 106 electrode-ions: Sends positive ions to the positive electrode (Strong and weak acids (HT only))
- C. Chemical changes case 106 electrode-ions: Uses electroplating language instead of electrolysis language (that lower means higher hydrogen ion concentration)
- D. Chemical changes case 106 electrode-ions: Chooses a product without checking the ion discharged (Reactions of acids)
Answer
The correct option is Chemical changes case 106 electrode-ions: Matches the ion movement to the correct electrode and product for that lower means higher hydrogen ion concentration.
Explanation
The correct option is Chemical changes case 106 electrode-ions: Matches the ion movement to the correct electrode and product for that lower means higher hydrogen ion concentration. It is correct because it directly supports the approved learning objective to (HT only) Explain that a lower pH means a higher hydrogen ion concentration in Strong and weak acids (HT only). 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
pH–concentration relationship
Students think a lower pH simply means a lower concentration of hydrogen ions, or they confuse pH with the amount of acid present.
Explain that pH is the negative logarithm of the hydrogen ion concentration: pH = –log[H⁺]. A lower pH value indicates a higher [H⁺] because the logarithm function is decreasing. For example, a solution with pH 3 has ten times the [H⁺] of a solution with pH 4, and a pH of 1 has 100 times the [H⁺] of a pH 3 solution. Emphasise that pH is a measure of acidity, not the quantity of acid added.
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