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Question:

25g of an unknown hydrocarbon upon burning produces 88g of CO2 and 9g of H2O. This unknown hydrocarbon contains:

22g of carbon and 3g of hydrogen

20g of carbon and 5g of hydrogen

24g of carbon and 1g of hydrogen

18g of carbon and 7g of hydrogen

Solution:

Correct option is B. 24g of carbon and 1g of hydrogen
CxHy + (x + y/4)O2 → xCO2 + y/2H2O
(25/M)x × 25M = 88/44 = 2
(25/M)y/2 × 25M = 9/18 = 0.5
C: x × 25M = 2
H: y/2 × 25M = 1
C2yHy = 24g mC + yg mH or 24:1 ratio by mass