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Question
The following experiment was performed in order to determine the formula of a hydrocarbon. The hydrocarbon X is purified by fractional distillation.
0.145 g of X was heated with dry copper (II) oxide and 224 cm3 of carbon dioxide was collected at S.T.P.
Calculate the empirical formula of X by the following step:
Deduce the ratio of atoms of each element in X (empirical formula).
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Solution
Percentage of C in X, = `0.12/0.145 xx 100` = 82.7%
Percentage of H in X, = `0.025/0.145 xx 100` = 17.3%
| Element | %age | Atomic weight | Atomic ratio | Simplest ratio | Simplest whole number ratio |
| C | 82.7 | 12 | `82.7/12` = 6.89 | `6.89/6.89` = 1 | 1 × 2 = 2 |
| H | 17.3 | 1 | `17.3/1` = 17.3 | `17.3/6.89` = 2.5 | 2.5 × 2 = 5 |
∴ Empirical formula of X = C2H5
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The following experiment was performed in order to determine the formula of a hydrocarbon. The hydrocarbon X is purified by fractional distillation.
0.145 g of X was heated with dry copper (II) oxide and 224 cm3 of carbon dioxide was collected at S.T.P.
Calculate the empirical formula of X by the following step:
Calculate the number of moles of carbon dioxide gas.
The following experiment was performed in order to determine the formula of a hydrocarbon. The hydrocarbon X is purified by fractional distillation.
0.145 g of X was heated with dry copper (II) oxide and 224 cm3 of carbon dioxide was collected at S.T.P.
Calculate the empirical formula of X by the following step:
Calculate the mass of carbon contained in this quantity of carbon dioxide and thus the mass of carbon in sample X.
