A Levels Chemistry

Measured values of the pressure, volume and temperature of a known mass of a gaseous
compound are to be substituted into the equation
pV = nRT
in order to calculate the relative molecular mass, M, of the compound.
Which conditions of pressure and temperature would give the most accurate value of M,?
pressure
temperature
A
high
high
high
low
low
high
D
low
low


Choice C is correct because:

Low pressure and high temperature conditions will make the gas behave more like an ideal gas. 

At low pressure, the gas particles are farther apart, making the effect of intermolecular forces negligible. 

High temperature increases the average kinetic energy of the gas particles, reducing the significance of intermolecular forces even further. 

As the ideal gas equation, pV = nRT, is based on the assumption of negligible intermolecular forces, these conditions would provide a more accurate value of Mr.

Choice A is incorrect because:

High pressure and high temperature conditions would cause the gas to deviate from ideal behavior. 

High pressure increases the impact of intermolecular forces, which could lead to less accurate results for Mr, even though high temperature is favorable.

Choice B is incorrect because:

High pressure and low temperature conditions both contribute to significant deviations from ideal gas behavior. 

High pressure increases intermolecular forces, and low temperature reduces the average kinetic energy of gas particles. These factors result in less accurate results for Mr.

Choice D is incorrect because:

Low pressure and low temperature conditions have mixed effects on gas behavior. 

Low pressure is favorable for ideal gas behavior, but low temperature reduces the average kinetic energy of gas particles, increasing the impact of intermolecular forces. This leads to less accurate results for Mr.

States of Matter | 2003 - M/J - 9701/1 | Q6