Three metal samples of magnesium, aluminium and iron were taken and rubbed with sand paper. These samples were then put separately in test tubes containing dilute hydrochloric acid. Thermometers were also suspended in each test tube so that their bulbs dipped in the acid. The rate of formation of bubbles was observed. The above activity was repeated with dilute nitric acid and the observations were recorded.
Generated by claude-sonnet-4-6 · 2026-06-15 06:47 · grounding stimulus
Model Answer
(a) The test tube containing magnesium showed the fastest rate of bubble formation and the highest temperature rise, because magnesium is the most reactive among the three metals.
(b) Iron did not react with dilute nitric acid (when the activity was repeated with it). However, with dilute HCl, all three metals react. (Note: If the question refers to dilute HCl specifically, none of the three metals is completely unreactive with it; all three displace hydrogen.)
> (Since sub-question (c) is incomplete — options (i) and (ii) are not provided — it cannot be answered.)
Source: Metals and Non-metals, Activity on reactivity of metals with dilute acids.
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Explanation
- For (a): Reactivity order is Mg > Al > Fe. More reactive metals react faster and release more heat, so the thermometer reads highest in the Mg test tube.
- For (b): The passage says the activity was also repeated with dilute nitric acid. Iron (and other metals) generally do not react with concentrated HNO₃ due to passivation, but with dilute HCl all three do react. If the examiner intends dilute HNO₃, iron may be the expected answer due to passivation with nitric acid. Read the full question context carefully.
- For (c): The sub-options were missing from the question — always write what is given; do not attempt incomplete sub-questions.