Why does zinc react with dilute sulphuric acid to give hydrogen gas but copper does not?

Answer 1

Zinc sulfate doesn't react to give zinc hydroxide and sulfuric acid. It dissolves in water, forming Zn2+ ions and sulfate ions, SO42-. However, SO42- is a weak base, and so it dissociates water forming HSO4-2 and OH-. Because HSO4- is the conjugate base of a strong acid, it is just a salt and does nothing further. However, because zinc hydroxide is soluble, no change is observed.

The reactions are:

ZnSO4 + H2O ---> Zn2+ + SO42- + H2O ---> Zn2+ + HSO4- + OH-

See discussion for alternative viewpoint.

Answer 2

Because zinc is lower than sodium in the metal activity series: (http://grandinetti.org/Teaching/Chem121/Lectures/SolutionReactions/assets/ActivitySeries.png) Therefore, zinc cannot replace the sodium in sodium hydroxide. Because zinc is lower than sodium in the metal activity series: (http://grandinetti.org/Teaching/Chem121/Lectures/SolutionReactions/assets/ActivitySeries.png) Therefore, zinc cannot replace the sodium in sodium hydroxide.

Answer 3

A simple explanation is that zinc is higher in the "reactivity series" than H and Cu is lower. This series is taught in the UK see "Doc Browns site link to question"

A more sophisticated explanation is around standard electrode potentials that gives a series that I used to call the Electrochemical series which is probably still being taught some where.

Answer 4

Zinc is above hydrogen in the reactivity series while copper is below. Since zinc has a higher tendency to lose electrons than hydrogen it then displaces hydrogen ions from solution.