Question
A fixed mass of a gas occupies a volume of 580 cm3 at a temperature of 17°C and a pressure of 750 mm. What volume will the gas occupy at that pressure and at a temperature of 47°C?
OR
Two gases of the same mass occupy at STP the volumes of 4480 mL and 5600 mL respectively. Find out the ratio of molar masses of the two gases.
Answer
V1 = 580 cm3 (initial volume)
T1 = 17°C = 17 + 273.15 = 290.15 K
T2 = 47°C = 47+273.15 = 320.15K
V2 = ? (final volume)
Charles’s Law: V_1\over T_1 = V_2\over T_2
⇒ V2 = V_1\over T_1 × T2
⇒ V2 = 580\over 290.15 × 320.15 = 638.16cm3
OR
Volume of Gas 1 (V1) = 4480 mL
Volume of Gas 2 (V2) = 5600 mL
For Gas 1: n1 = 4480/22400 = 0.2 moles
For Gas 2: n2 = 5600/22400 = 0.25 moles
From relation: M_1\over M_2 = n_2\over n_1
⇒ M_1\over M_2 = 0.25\over 0.2 = 5\over 4
The ratio of the molar masses of the two gases is 5:4.
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