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ICSE Class 9 Chemistry Question 4 of 29

Study of Gas Laws — Question 12

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Question

Question 12

What temperature would be necessary to double the volume of a gas, initially at S.T.P., if the pressure is decreased to 50% ?

Answer
Initial conditions [S.T.P.]Final conditions
P1 = Initial pressure of the gas = 1 atmP2 = Final pressure of the gas = 0.5 atm
V1 = Initial volume of the gas = VV2 = Final volume of the gas = 2V
T1 = Initial temperature of the gas = 273 KT2 = Final temperature of the gas = ?

By Gas Law:

P1×V1T1=P2×V2T2\dfrac{\text{P}_1\times\text{V}_1}{\text{T}_1} = \dfrac{\text{P}_2\times\text{V}_2}{\text{T}_2}

Substituting the values :

1×V273=0.5×2VT2T2=0.5×2×273T2=273 K\dfrac{1\times \text{V}}{273} = \dfrac{0.5\times\text{2\text{V}}}{\text{T}_2} \\[0.5em] \text{T}_2 = 0.5\times 2 \times 273\\[0.5em] \text{T}_2 = 273\text{ K}

∴ Final temperature of the gas = 273 K