Certified Transport Registered Nurse Certification Practice Exam

Which gas law explains the rate of effusion or diffusion of a gas in relation to its molecular weight?

1. Avogadro's Law

2. Boyle's Law

3. Charles' Law

4. Graham's Law

The correct answer is: Graham's Law

Graham's Law is the principle that describes how the rate of effusion or diffusion of a gas is inversely proportional to the square root of its molecular weight. This means that lighter gases will effuse or diffuse more rapidly than heavier gases. The mathematical formulation of Graham's Law indicates that if two gases are at the same temperature and pressure, the ratio of their rates of effusion or diffusion is equal to the inverse ratio of the square roots of their molar masses. This fundamental relationship showcases how molecular weight directly influences the behavior of gases in terms of their movement through openings or mixing with other gases. In practical applications, Graham's Law explains phenomena such as why helium fills balloons more quickly than heavier gases like oxygen. The other gas laws, such as Avogadro's Law, Boyle's Law, and Charles' Law, address different relationships concerning the properties of gases. Avogadro's Law relates the volume of gas to the number of moles, Boyle's Law describes the relationship between pressure and volume at constant temperature, and Charles' Law relates volume to temperature at constant pressure. Each of these laws provides essential insights into gas behavior but does not specifically address the influence of molecular weight on effusion or diffusion rates like Graham's Law does.