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02/10/2020 3:49 pm
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A solution containing 1.8 g of a compound (empirical formula CH2O) in 40 g of water is observed to freeze at -0.465°C. The molecular formula of the compound is (Kf of water = 1.86 kg K mol-1)
(a) C2H4O2
(b) C3H6O3
(c) C4H8O4
(d) C6H12O6
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02/10/2020 3:56 pm
(d) C6H12O6
Explanation:
ΔTf = Kf x m
M = 1000 x Kf x w2 (solute)/ΔTf x w1 (solvent)
= (1000 x 1.86 x 1.8)/(0.465 x 40)
=> M = 180
Molecular formula = (empirical formula)n
n = Molecular mass/Empirical formula mass
= 180/30 = 6
Molecular formula = (CH2O)6 = C6H12O6