Chemistry
(i) Calculate:
The number of moles in 12g of oxygen gas. [O = 16]
The weight of 1022 atoms of carbon.
[C = 12, Avogadro’s No. = 6 x 1023]
(ii) Molecular formula of a compound is C6H18O3. Find its empirical formula.
Stoichiometry
ICSE 2019
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Answer
(i) Gram molecular mass of oxygen = 32 g = 1 mole
32 g = 1 mole
∴ 12 g = x 12 = 0.375 moles.
6 x 1023 atoms of carbon weigh = 12 g
∴ 1022 atoms of carbon will weigh = x 1022 = 0.2 g.
Hence, number of moles = 0.375 moles and weight of 1022 atoms of carbon = 0.2 g.
(ii) Molecular formula of the compound is C6H18O3
Molecular formula = n x (Empirical Formula)
C6H18O3 can be written as 3(C2H6O)
∴ Molecular formula = 3 x (C2H6O)
∴ Empirical Formula of the compound is C2H6O
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