Question:
A vessel contains 1.6 g of dioxygen at STP (273.15K, 1 atm pressure). The
gas is now transferred to another vessel at a constant temperature, where
the pressure becomes half of the original pressure. Calculate
(i) the volume of the new vessel.
(ii) a number of molecules of dioxygen.
Solution:
(i) Moles of oxygen = 1.6/32 = 0.05mol
At STP, 1 mol of O2 = 22.4L
Then volume of O2 = 22.4 × 0.05 = 1.12L
V1 = 1.12L
V2 =?
P1 = 1atm
P2 = ½ = 0.5atm
According to Boyle’s law, p1V1 = p2V2
Substituting the values
V2 = 1 × 1.12/0.5 = 2.24L
(ii) No of molecules in 1.6g or 0.005mol = 6.022 × 1023 × 0.05 = 3.011 × 1022
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