Question

An unknown compund contains only carbon, hydrogen, and oxygen. combustion of 2.5 g of this compound produced 3.67g of carbon dioxide and 1.5 g of water. How many moles of carbon were in the orginal sample?

Answer 1

To find the number of moles of carbon in the original sample, we first need to determine the molecular formula of the unknown compound.

First, let's calculate the number of moles of carbon dioxide (CO2) produced in the combustion reaction:

Number of moles of CO2 = mass of CO2 / molar mass of CO2
= 3.67 g / (12.01 g/mol + 2*16.00 g/mol)
≈ 0.098 moles

Next, let's calculate the number of moles of water (H2O) produced in the combustion reaction:

Number of moles of H2O = mass of H2O / molar mass of H2O
= 1.5 g / (2*1.01 g/mol + 16.00 g/mol)
≈ 0.083 moles

The number of moles of carbon in the original sample can be determined by comparing the mole ratio between CO2 and carbon in the balanced chemical equation for combustion. The balanced equation for the combustion of carbon can be written as:

C + O2 → CO2

From the balanced equation, we see that the mole ratio between CO2 and carbon is 1:1.

Therefore, the number of moles of carbon in the original sample is approximately 0.098 moles.