Question

Which of the following is true for a given mass of a gas at constant pressure?

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

Explanation for the correct option:

Charles' law: At constant pressure, for a given mass of a gas, volume is directly proportional to temperature. As temperature rises, volume rises and as temperature decreases, volume decreases.

$V\propto T$ where V= Volume of the gas T=Temperature of the gas

or $V=kT$

At constant pressure, the volume of a given mass of a gas increases or decreases by 1/273 of its volume at 0° C for every one-degree rise or fall in the temperature respectively.

$V_T=V_0+\left(\frac{1}{273.15}{V}_0\right)T$

If V_T=0, T (in Celsius) comes out to be -273.15° C

At -273.15° C or 0 K, the volume of the gas becomes zero. This temperature is called as absolute zero temperature.

Therefore, the graph shows zero volume at -273° C on the negative x-axis.

Explanation for the incorrect options:

(a) Zero volume is depicted against 0° C instead of 0 K as the temperature is indicated in °C on the x-axis.

(b) Zero volume is depicted against -273.15 K instead of 0 K as the temperature is indicated in K on the x-axis.

(d) In this graph also, zero volume is depicted at 0° C instead of zero K as the temperature is shown in ° C on the y-axis.

Hence, option (c) is correct.