A 1.24g sample of a hydrocarbon, when completely burned in excess of O2(g), yields 4.04g CO2 and 1.24g H20. Determine the empirical formula.
CnHm + O2 → CO2 + H2O
4.04g of CO2*(1 mole of CO2/44.01g of CO2)=moles of CO2=0.0913g of CO2
1 mole of CO2=1 mole C, moles of CO2=moles of C
1.24 g of H20 *(1mole of H20/18 g of H20)=moles of H20=0.689
1 mole of H20=2 moles of H
2*moles of H20= moles of H=0.1376
divide the number of moles of H by moles of C
you should calculate C=1 H=2
Combustion reaction is
CH2 + O2 → CO2 + H2O
The reaction in the bottom of the post above is unbalanced
The balanced reaction is
2CH2 + 3O2--> 2CO2 + 2H20
I agree with 0.0918 mols C and 0.137 mols H but not the formula.
0.137/0.0918 = about 1.5; is that C2H3?
And the balanced equation is
4C2H3 + 11O2 ==> 8CO2 + 6H2O
I've not heard of C2H3?
To determine the empirical formula of a hydrocarbon, you need to use the given information about the masses of the reactants and products involved in the combustion reaction.
Let's break down the problem step by step:
1. Determine the moles of carbon dioxide (CO2):
To find the moles of CO2, divide the given mass (4.04g) by its molar mass. The molar mass of CO2 is calculated by adding the atomic masses of carbon (C) and oxygen (O):
Molar mass of CO2 = (12.01g/mol) + 2*(16.00g/mol) = 44.01g/mol
Moles of CO2 = 4.04g / 44.01g/mol
2. Determine the moles of water (H2O):
To find the moles of H2O, divide the given mass (1.24g) by its molar mass. The molar mass of H2O is calculated by adding the atomic masses of hydrogen (H) and oxygen (O):
Molar mass of H2O = 2*(1.01g/mol) + 16.00g/mol = 18.02g/mol
Moles of H2O = 1.24g / 18.02g/mol
3. Determine the moles of carbon (C):
Since there is no other source of carbon in the reactants and products except for the hydrocarbon, the moles of carbon can be equated to the moles of CO2. This is because one mole of CO2 contains one mole of carbon.
Moles of carbon (C) = Moles of CO2
4. Determine the moles of hydrogen (H):
Since there is no other source of hydrogen in the reactants and products except for water, the moles of hydrogen can be equated to the moles of H2O. This is because one mole of H2O contains two moles of hydrogen.
Moles of hydrogen (H) = 2 * Moles of H2O
5. Determine the empirical formula:
The empirical formula represents the simplest whole-number ratio of atoms in a compound. Divide the moles of each element (C and H) by the smallest number of moles calculated, to get a whole number ratio.
In this case, since the moles of carbon and moles of hydrogen are the same, we can simply write the empirical formula as:
C:1 H:1
Therefore, the empirical formula of the hydrocarbon is CH.