Ethylene glycol, commonly used as automobile antifreeze, contains only carbon, hydrogen, and oxygen. Combustion analysis of a 23.46 mg sample yields 20.42 mg of H2O and 33.27 mg of CO2. What is the empirical formula of ethylene glycol? What is its molecular formula if it has a molecular weight of 62.0?

검증된 단계별 안내

Calculate the moles of carbon in the CO2 produced. Use the molar mass of CO2 (44.01 g/mol) and the fact that each mole of CO2 contains one mole of carbon.

Calculate the moles of hydrogen in the H2O produced. Use the molar mass of H2O (18.02 g/mol) and the fact that each mole of H2O contains two moles of hydrogen.

Determine the mass of carbon and hydrogen in the original sample using their respective moles and atomic masses (C: 12.01 g/mol, H: 1.008 g/mol).

Subtract the mass of carbon and hydrogen from the total mass of the sample to find the mass of oxygen. Then, calculate the moles of oxygen using its atomic mass (O: 16.00 g/mol).

Determine the empirical formula by finding the simplest whole number ratio of moles of C, H, and O. Then, use the given molecular weight to find the molecular formula by comparing the empirical formula mass to the molecular weight.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Combustion Analysis

Combustion analysis is a technique used to determine the elemental composition of organic compounds. In this process, a sample is burned in excess oxygen, producing carbon dioxide and water. The masses of these products are measured, allowing for the calculation of the amounts of carbon, hydrogen, and sometimes oxygen in the original sample, which is essential for determining empirical formulas.

Empirical Formula

The empirical formula represents the simplest whole-number ratio of the elements in a compound. It is derived from the moles of each element calculated from the combustion analysis data. For ethylene glycol, the empirical formula can be determined by converting the mass of carbon and hydrogen obtained from the combustion products into moles and simplifying the ratio.

Molecular Formula

The molecular formula indicates the actual number of atoms of each element in a molecule of a compound. It can be derived from the empirical formula by multiplying it by a whole number, which is determined by dividing the compound's molar mass by the molar mass of the empirical formula. In this case, knowing the molecular weight of ethylene glycol allows for the calculation of its molecular formula from the empirical formula.