Question

Which property is constant in the combined gas law?

Answer 1

Answer: The correct answer is number of particles.

Explanation:

Ideal gas law states the relationship between the variables of the gas. the variables are pressure, volume and temperature of the gas.

This combined gas law is calculated by the three laws:

1) Boyle's Law: This law states that pressure of the gas is inversely proportional to the volume of the gas at constant temperature and number of moles.

$P\propto \frac{1}{V}$     (At constant temperature and number of moles)

2) Charles' Law: This law states that volume of the gas is directly proportional to the temperature of the gas at constant pressure and number of moles.

$V\propto T$     (At constant pressure and number of moles)

3) Gay-Lussac's Law: This law states that pressure of the gas is directly proportional to the temperature of the gas at constant volume and number of moles.

$P\propto T$     (At constant volume and number of moles)

From the above three laws, the combined gas law equation becomes:

$\frac{PV}{T}=k$

Or,

$\frac{P_1V_1}{T_1}=\frac{P_2V_2}{T_2}$

As seen clearly above, number of particles in the above combined gas law equation remains constant.

Answer 2

Number of particles

combined gas law : P1V1/T1 = P2V2/T2