3.2.4—Acids with reactive metals
- Syllabus
- First assessment 2025
- Objective
- 3.2.4
- Level
- SL
Metals with Dilute Acids
A metal above hydrogen in the activity series can donate electrons to acid and release hydrogen gas; a metal below hydrogen, such as copper, does not react with dilute hydrochloric acid.
metal+acid→salt+H2(g)
Balance the electron transfer behind the molecular equation: metal atoms are oxidized and 2H⁺ + 2e⁻ → H₂ is the reduction. Use the metal charge and acid anion to construct the salt rather than assuming every metal forms a 2+ ion.
Predicting Hydrogen Release
[ 2 ]
Outline, using an ionic equation, what is observed when magnesium powder is added to a solution of ammonium chloride.
Electron Transfer Reactions Summary
Retrieve the route: assign oxidation states, balance half-equations, predict displacement, label cells, trace electrons and ions, follow organic redox pathways, calculate potentials and choose electrolysis products.
Check electron loss/gain, anode/cathode versus polarity, spontaneous sign, salt-bridge direction, ions present, organic functional-group direction and object-cathode placement.