Question

A sample of gas at 300 K has a volume of 2.0 liters. At what temperature will the volume decrease to 1.0 liter if the pressure is kept constant?

Answer 1

Pv/t=c 
Therefore 

v/t=c 
2/300=1/t2 
t2=150K 

Answer 2

Answer : The temperature will be, 150 K

Explanation :

Charles' Law : This law states that volume of 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)

or,

$\frac{V_1}{T_1}=\frac{V_2}{T_2}$

where,

$V_1$ = initial volume of gas = 2.0 L

$V_2$ = final volume of gas = 1.0 L

$T_1$ = initial temperature of gas = 300 K

$T_2$ = final temperature of gas = ?

Now put all the given values in the above formula, we get the final temperature of gas.

$\frac{2.0L}{300K}=\frac{1.0L}{T_2}$

$T_2=150K$

Therefore, the temperature will be, 150 K