Question

According to Avogadro’s law the volume of a gas will ⋯⋯as ⋯⋯if ⋯⋯are held constant.
(A) increases, number of moles; P $\And $ T
(B) decreases, number of moles; P $\And $ T
(C) increases, T $\And $ P, number of moles
 (D) decreases, P $\And $ T, number of moles

Answer 1

Hint: The Avogadro’s law gives us the relation between volume and number of molecules of a gas. The law is valid at constant temperature and pressures. Since this law links pressure, temperature, volume and amount of substance in a gas, it’s closely related to the ideal gas equation.

Complete step by step answer:
- Let us in detail try to understand Avogadro's law. It gives us the relation between volume and number of molecules of a gas. This law was developed by an Italian chemist Amedeo Avogadro in the year 1811.
- According to Avogadro’s law at the same pressure and temperature, equal volumes of all gases will contain equal numbers of molecules. Or in other words the volume of a gas will be directly proportional to the amount of substance or number of moles of gas present in the sample which we consider.
 - The Avogadro’s law’s mathematical expression can be written as follows
\[V\propto n\]
Where V is the volume of gas and n is the number of moles of gas present in the sample which we take. Remind that this relation holds only if we keep pressure and temperature constant. By introducing the proportionality constant (k) we could write as follows
\[V=kn\]

- So from the above relation it’s clear that the volume of gas will increase as the number of moles if the temperature (T) and pressure (P) are held constant.
So, the correct answer is “Option C”.

Note: The Avogadro’s law can be verified in real life situations. For example a balloon filled with the helium gas will weigh much less than the identical balloon filled with air. Both of these balloons have the same number of molecules in it. Since the helium has lower atomic mass than nitrogen or oxygen molecules in air, the helium balloon will be lighter than the balloon filled with air.