A quality-control chemist is identifying an unknown compound.
Analysis shows that the simplest ratio of carbon atoms to hydrogen atoms to oxygen atoms in the compound is 1:1:11:1:11:1:1.
Four molecular formulae are proposed.
| Proposal | Molecular formula |
|---|---|
| A | C2H2O2\mathrm{C_{2}H_{2}O_{2}}C2H2O2 |
| B | C4H4O4\mathrm{C_{4}H_{4}O_{4}}C4H4O4 |
| C | C2H4O2\mathrm{C_{2}H_{4}O_{2}}C2H4O2 |
| D | C3H6O3\mathrm{C_{3}H_{6}O_{3}}C3H6O3 |
Relative atomic masses (ArA_rAr): C = 12.0, H = 1.0, O = 16.0
Which two proposals could be the molecular formula of the unknown compound?
Explain your answer.
The unknown compound has an Mr M_r\,Mr of 116.
Calculate the relative formula mass (MrM_rMr) of each proposal you chose in (a), and give the proposal that is the unknown compound.
A student writes this equation for the complete combustion of compound C.
2C2H4O2+3O2→4CO2+4H2O \mathrm{2C_{2}H_{4}O_{2} + 3O_{2} \rightarrow 4CO_{2} + 4H_{2}O} 2C2H4O2+3O2→4CO2+4H2OUse relative formula masses to show whether the equation is balanced.
102 exam-style questions on OCR GCSE Chemistry 2.1 Purity and separating mixtures, covering 2.1.1 Pure substances and melting point data, 2.1.2 Relative formula mass and empirical formula, 2.1.3 Formulations as useful mixtures, 2.1.4 Techniques for separating mixtures, and 2.1.5 Chromatography and Rf values. Each one has a worked solution and a mark scheme showing where the marks go.