Physical properties of hydrogen

  • colourless, odourless gas
  • insoluble in water
  • less dense than air
  • hydrogen is diatomic, H2

Preparing and collecting hydrogen gas

Precipitation of hydrogen gas

We prepare hydrogen by reacting zinc or magnesium with dilute hydrochloric acid:

Zn + 2HCl → ZnCl2 + H2

Mg + 2HCl → MgCl2 + H2

  • hydrogen is insoluble in water, so can collect it using a gas jar in a trough of water.
  • dilute hydrochloric acid reacts vigorously with magnesium and can be dangerous.

Test for hydrogen

A lit splint applied to hydrogen gas will result in a popping sound.

Hydrogen uses

  • making the fats in margarines solidify
  • weather balloons
  • potential as a clean fuel