1.50 g sample of hydrocarbon undergoes complete combustion to produce
4.40 g of CO2 and 2.70 g of H2O. What is the empirical formula of this compound? In
addition, its molecular weight has been determined to be about 78. What is the
molecular formula?
Answers
Answer:
: A 1.50 g sample of hydrocarbon undergoes complete combustion to produce 4.40 g of CO2 and
2.70 g of H2O. What is the empirical formula of this compound?
Solution:
1) Determine the grams of carbon in 4.40 g CO2 and the grams of hydrogen in 2.70 g H2O.
carbon: 4.40 g x (12.011 g / 44.0098 g) = 1.20083 g
hydrogen: 2.70 g x (2.0158 g / 18.0152 g) = 0.3021482 g
2) Convert grams of C and H to their respective amount of moles.
carbon: 1.20083 g / 12.011 g/mol = 0.09998 mol
hydrogen: 0.3021482 g / 1.0079 g/mol = 0.2998 mol
3) Divide each molar amount by the lowest value, seeking to modify the above molar amounts into small, whole
numbers.
carbon: 0.09998 mol / 0.09998 mol = 1
hydrogen: 0.2998 mol / 0.09998 mol = 2.9986 = 3
We have now arrived at the answer: the empirical formula of the substance is CH3
Explanation: