IB Chemistry SL 3.2.4 Acids with Reactive Metals Questions

Use real SL exam questions to predict metal–acid reactions, write ionic equations and identify hydrogen observations.

Exam points

Write the ionic equation for a reactive metal with a dilute acid or ammonium ion, showing hydrogen gas formation and correct charges and state symbols.
Use the metal reactivity and acid identity to predict whether reaction occurs and describe the observable gas evolution or disappearance of the metal.
Identify the products and the acid/metal roles in reactive-metal reactions, including hydrogen or ammonia where the stated reactants require it.

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Study 3.2.4—Acids with reactive metals conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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Two hydrides of nitrogen are ammonia and hydrazine, $\mathrm{N}_{2} \mathrm{H}_{4}$ . One derivative of ammonia is methanamine whose molecular structure is shown below.

Figure for Question IB Chemistry SL 3.2.4 Acids with Reactive Metals Questions question 1 — IB Chemistry SL

Outline, using an ionic equation, what is observed when magnesium powder is added to a solution of ammonium chloride.

bubbles

OR

gas

OR

magnesium disappears
$2 \mathrm{NH}_{4}^{+}(\mathrm{aq})+\mathrm{Mg}(\mathrm{~s}) \rightarrow \mathrm{Mg}^{2+}(\mathrm{aq})+2 \mathrm{NH}_{3}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g})$

Marking guidance:

Do not accept "hydrogen" without reference to observed changes. Accept "smell of ammonia".

Accept $2 \mathrm{H}^{+}(\mathrm{aq})+\mathrm{Mg}(\mathrm{s}) \rightarrow \mathrm{Mg}^{2+}(\mathrm{aq}) +\mathrm{H}_{2}(\mathrm{~g})$

Equation must be ionic.

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IB Chemistry SL 3.2.4 Acids with Reactive Metals Questions question 1