Question

Select the parameter that needs to be constant for Charles law:

• A. Pressure
• B. Temperature
• C. Volume
• D. Surface area

Answer 1

The correct option is A

Pressure

The explanation for the correct option:

Option A

Charle’s law:

• According to this law, at constant pressure, the volume of a fixed amount of a gas is directly proportional to its absolute temperature.

Mathematically:

V α T (At constant pressure).

V = K T ( K is constant).

V = Volume of gas

T = Temperature

The explanation for incorrect options:

• Charle's law is not applicable when we keep constant volume, surface area, and temperature.
• If the temperature is constant then it becomes Boyle's law, which states that the pressure exerted by a gas (of a given mass, kept at a constant temperature) is inversely proportional to the volume occupied by it, Mathematically, ${\mathrm{P}}_1{\mathrm{V}}_1={\mathrm{P}}_2{\mathrm{V}}_2$.
• If the pressure is constant then it becomes Gay-Lussac’s law, which states that the pressure (P) of a fixed mass of gas held at a constant volume is directionally proportional to its Kelvin temperature (T), Mathematically, $\frac{{\mathrm{P}}_1}{{\mathrm{T}}_1}=\frac{{\mathrm{P}}_2}{\mathrm{T}2}$.
• The surface area doesn't play any role in Charle's law.

Therefore, option A is correct.