Question

(a) describe how the percentages of carbon and hydrogen in an organic compound are determined. state the measurements which are made. 8 marks

Explanation:

To determine the percentages of carbon and hydrogen in an organic compound, the compound is burned in excess oxygen. Carbon is converted to carbon - dioxide and hydrogen to water. The mass of carbon - dioxide is measured to find the mass of carbon (using the molar mass ratio of carbon in carbon - dioxide), and the mass of water is measured to find the mass of hydrogen (using the molar mass ratio of hydrogen in water). These masses are then used to calculate the percentages in the original organic compound.

Answer:

The organic compound is burned in excess oxygen. The mass of carbon - dioxide produced is measured. From the mass of carbon - dioxide, the mass of carbon in the original compound can be calculated using the ratio of the molar mass of carbon to the molar mass of carbon - dioxide. Similarly, the mass of water produced is measured, and from it, the mass of hydrogen in the original compound is calculated using the ratio of the molar mass of hydrogen to the molar mass of water. Then, the percentages of carbon and hydrogen in the original organic compound are calculated based on the masses of carbon, hydrogen, and the original compound.