Question

A 0.3825 g sample of an unknown substance was analyzed and produced 0.3358g CO2 and 0.2062g H2O upon combustion. Determine the % C and % H in the substance.

A) % C: 87.90%, % H: 12.10%
B) % C: 55.32%, % H: 44.68%
C) % C: 62.60%, % H: 37.40%
D) % C: 78.21%, % H: 21.79%

Answer 1

To determine the percent composition of carbon and hydrogen in the unknown substance, we need to calculate the masses of carbon and hydrogen in the sample. The correct percent composition is approximately 24.01% C and 6.01% H.

Step-by-step explanation:

To determine the percent composition of carbon and hydrogen in the unknown substance, we need to calculate the masses of carbon and hydrogen in the sample. From the given data, the sample produced 0.3358g CO2 and 0.2062g H2O upon combustion.

First, we can calculate the mass of carbon in the sample by using the molar mass of CO2. The molar mass of CO2 is 44.01 g/mol, so the mass of carbon in the sample is (0.3358g CO2) * (12.01 g C / 44.01 g CO2) = 0.0918g C.

Similarly, we can calculate the mass of hydrogen in the sample by using the molar mass of H2O. The molar mass of H2O is 18.02 g/mol, so the mass of hydrogen in the sample is (0.2062g H2O) * (2.02 g H / 18.02 g H2O) = 0.0230g H.

To determine the percent composition, divide the mass of each element by the total mass of the sample and multiply by 100%. The total mass of the sample is 0.3825g.

Percent C = (0.0918g C / 0.3825g sample) * 100% = 24.01%

Percent H = (0.0230g H / 0.3825g sample) * 100% = 6.01%

The correct answer is not provided in the multiple-choice options. The correct percent composition is approximately 24.01% C and 6.01% H.