Chemistry
Define:
- Mole
- Gay Lussac's law
(ii) A cylinder contains 68 g of ammonia gas at s.t.p.
(1) What is the volume occupied by this gas ?
(2) How many moles of ammonia are present in the cylinder ?
(3) How many molecules of ammonia are present in the cylinder ?
[N—14, H—1]
Mole Concept
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Answer
(i) Mole — A mole is the amount of pure substance containing the same number of chemical units as there are atoms in exactly 12 grams of carbon-12. [6C12]
(ii) Gay Lussac's law — When gases react, they do so in volumes which bear a simple ratio to one another, and to the volume of the gaseous product, provided that all the volumes are measured at the same temperature and pressure.
(ii) (1) Gram molecular mass of ammonia = N + 3(H) = 14 + 3 = 17 g.
17 g. occupies 22.4 lit. of vol.
∴ 68 g will occupy = x 68 = 89.6 lit.
Hence, volume occupied by this gas = 89.6 lit.
(2) 17 g = 1 mole
∴ 68 g = x 68 = 4 moles.
(3) 1 mole = 6 × 1023
∴ 4 moles = 4 x 6.023 × 1023 molecules.
Hence, Moles = 4 and molecules = 24.092 × 1023 molecules
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