Question

A sample of a hydrocarbon is combusted completely in O₂(g) to produce 21.83 g CO₂(g), 4.47 g H₂O(g), and 311 kJ of heat.

What is the mass of the hydrocarbon sample that was combusted?

Answer 1

The mass of the hydrocarbon combusted can be calculated by determining the moles of carbon and hydrogen from the mass of CO₂ and H₂O produced, and then converting those moles back to grams.

Step-by-step explanation:

To find the mass of the hydrocarbon that was combusted, we first need to determine the masses of carbon and hydrogen that were present in the hydrocarbon. By using combustion analysis, the carbon in the hydrocarbon is converted to CO₂ and the hydrogen to H₂O. We can use the molar masses of CO₂ and H₂O to calculate the moles of carbon and hydrogen, and from these values, we can determine the mass of carbon and hydrogen in the original hydrocarbon.

The molar mass of CO₂ is 44.01 g/mol, and H₂O has a molar mass of 18.02 g/mol. Therefore, from 21.83 g of CO₂, we can calculate the moles of carbon present (21.83 g / 44.01 g/mol), and from 4.47 g of H₂O, the moles of hydrogen present (4.47 g / 18.02 g/mol). Each mole of CO₂ corresponds to one mole of carbon, and each mole of H₂O corresponds to two moles of hydrogen atoms from the original hydrocarbon.

Once the moles of carbon and hydrogen are calculated, they need to be converted back to grams using the molar mass of carbon (12.01 g/mol) and hydrogen (1.008 g/mol). The sum of these masses will give the total mass of the hydrocarbon that was combusted.