ICSE Class 9 Chemistry Question 24 of 29

Study of Gas Laws — Question 9

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Question

Question 9

A gas at 240 K is heated to 127°C. Find the percentage change in the volume of the gas (pressure remaining constant).

Answer

V1 = Initial volume of the gas = V cc
T1 = Initial temperature of the gas = 240 K
T2 = Final temperature of the gas = 127°C = 127 + 273 = 400 K
V2 = Final volume of the gas = ?

By Charles' Law:

V1T1=V2T2\dfrac{\text{V}_1}{\text{T}_1} = \dfrac{\text{V}_2}{\text{T}_2}

Substituting the values :

V240=V2400V2=400×V240V2=5×V3\dfrac{\text{V}}{240} = \dfrac{\text{V}_2}{400} \\[1em] \text{V}_2 = \dfrac{400 \times \text{V}}{240} \\[1em] \text{V}_2 = \dfrac{5\times \text{V}}{3}

Increase in vol. = 5V3\dfrac{5\text{V}}{3} - V = 2V3\dfrac{2\text{V}}{3}

Percentage increase in vol. = IncreaseOriginal\dfrac{\text{Increase}}{\text{Original}} x 100 = 2V3V\dfrac{2\text{V}}{3\text{V}} x 100 = 66.67%

∴ Percentage increase in the volume of the gas = 66.67%