Question #fabcb

1 Answer
Alfredo T.
Jun 3, 2015

Consider a sample of 182 grams of such substance (approximately one mole). It contains:

182 grams ⋅ 0.4012.01 g/mol=6.06 mol of C atoms;

182 grams ⋅ 0.0671.008 g/mol=12.1 mol of H atoms;
182 grams ⋅ 0.53316.00 g/mol=6.06 mol of C atoms;

Given that in a molecule there are integer number of atoms, that equal numbers of moles means equal numbers of atoms, we deduce that in each molecule there are:
a) the same number of carbon and oxygen atoms, i.e. 6
b) double number of H atoms, that is 12.

The molecular formula is therefore: C6H12O6.
The true molecular mass should be:
C⋅6+H⋅12+O⋅6=
12,0⋅6+1,0⋅12+16,0⋅6=180
A value of 182 deduced from osmosis experiments is just one percent bigger, as due to experimental errors.

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