大象传媒

Avogadro's law - higher tier

states:

  • equal volumes of different gases contain an equal number of particles under the same conditions of temperature and pressure

This means that equal numbers of of gases occupy the same volume under the same conditions of temperature and pressure. For example:

  • 1 mol of hydrogen gas occupies the same volume as 1 mol of methane gas
  • 10 mol of nitrogen monoxide gas occupy the same volume as 10 mol of argon gas
  • the volume of 1 mol of any gas under these conditions is 24 dm3

Avogadro's law can be used to calculate the volumes of gases involved in reactions.

Using Avogadro's law

Hydrogen reacts with chlorine to form hydrogen chloride:

H2(g) + Cl2(g) 鈫 2HCl(g)

The mole ratio of hydrogen to chlorine is 1:1. This means, for example, that in terms of volume:

  • 1 cm3 of hydrogen reacts with excess chlorine to produce 2 cm 3 of hydrogen chloride
  • 250 cm3 of hydrogen reacts with excess chlorine to produce 250 cm3 of hydrogen chloride

The mole ratio of hydrogen to hydrogen chloride is 1:2. This means, for example:

  • 1 cm3 of hydrogen produces 2 cm3 of hydrogen chloride
  • 250 cm3 of hydrogen produces 500 cm3 of hydrogen chloride

Question

Nitrogen reacts with hydrogen to produce ammonia:

N2(g) + 3H2(g) 鈫 2NH3(g)

Calculate the volume of ammonia that can be produced from 150 cm3 of hydrogen and an excess of nitrogen.

Question

Hydrogen reacts with oxygen to produce steam: 2H2(g) + O2(g) 鈫 2H2O(g)

Calculate the volume of steam that can be produced from 50 cm3 of oxygen and an excess of hydrogen.