When 1.63 g sample of an unknown hydrocarbon is completely burned in oxygen, 4.97 g of CO2 are produced. What is the percentage by mass of hydrogen in this hydrocarbon?
THANK YOUU
Found out the formula:
4CH+5O2--> 4CO2+2H2O
then found out the moles of CH= 0.1251
I don't know where to go from here.
What's 4CH? 4CH doesn't make sense to me. The hydrocarbon must be CxHy.
Convert CO2 to mols.
mols CO2 = g/molar mass = 4.97/44 = about 0.11 but you need to do it more accurately. Now convert mols CO2 to grams C. That is mols C x atomic mass C = 0.11 x 12 = about 1.3
%C = (mass C/mass sample)*100 = about (1.3/1.63)*100 = about 83%
So %H must be 100 - %C = ?
To determine the percentage by mass of hydrogen in the unknown hydrocarbon, you need to calculate the mass of hydrogen in the hydrocarbon sample and then calculate the percentage.
1. Start by calculating the number of moles of carbon dioxide produced in the reaction using its molar mass. The molar mass of CO2 is 44.01 g/mol.
Moles of CO2 = Mass of CO2 / Molar mass of CO2
= 4.97 g / 44.01 g/mol
≈ 0.1129 mol
2. From the balanced chemical equation, you know that for every mole of CO2 produced, there are 2 moles of water formed. Therefore, the number of moles of water formed is also 0.1129 mol.
3. Now, since 2 moles of water are formed from 1 mole of the unknown hydrocarbon, this hydrocarbon must contain twice the number of moles of hydrogen compared to the moles of water produced.
Moles of hydrogen = 2 × Moles of water
= 2 × 0.1129 mol
= 0.2258 mol
4. Finally, calculate the mass of hydrogen based on the number of moles and the molar mass of hydrogen, which is 1.00784 g/mol.
Mass of hydrogen = Moles of hydrogen × Molar mass of hydrogen
= 0.2258 mol × 1.00784 g/mol
≈ 0.2277 g
5. To find the percentage by mass of hydrogen, divide the mass of hydrogen by the mass of the original hydrocarbon sample and multiply by 100.
Percentage by mass of hydrogen = (Mass of hydrogen / Mass of hydrocarbon sample) × 100
= (0.2277 g / 1.63 g) × 100
≈ 13.99%
Therefore, the percentage by mass of hydrogen in the unknown hydrocarbon is approximately 13.99%.