a certain mass of gas occupies volume of 2 litre at STP. keeping the pressure constant , at what temperature would the gas occupy a volume of 4 litre?

Given: Volume = 2L
​At STP, Pressure, P₁ = 1 atm and Temperature, T₁ = 273 K
Final Volume, V₂ = 4L 
To find: Final temperature, T₂
​Solve: As we know
PV = nRT
Now, for given number of moles at constant pressure volume is directly proportional to temperature. We can write as

$$\begin{gathered} \frac{{\text{V}}_{\text{2}}}{{\text{V}}_{\text{1}}}=\frac{{\text{T}}_{\text{2}}}{{\text{T}}_{\text{1}}} \\ \frac{4}{2}=\frac{{\text{T}}_{\text{2}}}{273} \\ {\text{T}}_{\text{2}} = 273\times 2 \\ = 546 \text{K} \end{gathered}$$

Temperature in degree Celsius = 546-273
= 273⁰C
The correct option is (2).