At normal temperature and pressure, 1 mole (= 4 g)
of helium encloses a volume of 22.4 litre. Determine
the speed of sound in helium. (For helium, y = 1.67,
1 atmospheric pressure = 105 Nm-3)
Hint: The density of helium is
4 g
4 x 10-kg
4
22.4 litre
22.4
Ans. 967 m s-1
kg m-3.
3.
22.4 x 10-3
m
Answers
Radius of hydrogen atom, r = 0.5 Å = 0.5 × 10-10 m
Volume of hydrogen atom = (4/3) π r3
= (4/3) × (22/7) × (0.5 × 10-10)3
= 0.524 × 10-30 m3
Now, 1 mole of hydrogen contains 6.023 × 1023 hydrogen atoms.
∴ Volume of 1 mole of hydrogen atoms, Va = 6.023 × 1023 × 0.524 × 10–30
= 3.16 × 10–7 m3
Molar volume of 1 mole of hydrogen atoms at STP,
Vm = 22.4 L = 22.4 × 10–3 m3
∴VaVm=3.6×10−722.4×10−3=7.08×104
Hence, the molar volume is 7.08 × 104 times higher than the atomic volume.
The ratio is so large because inter-atomic separation in hydrogen gas is large.
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Answer:
Explanation:
967m/s