A welding fuel gas contains C and H only. Burning a small sample of it in oxygen gives , of water and no other products. A volume of (at STP) of this welding gas is found to weigh . The molecular f

Question

A welding fuel gas contains C and H only. Burning a small sample of it in oxygen gives  ,  of water and no other products. A volume of  (at STP) of this welding gas is found to weigh . The molecular formula of the compound is:

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Strategy:
 Combustion analysis allows us to find the empirical formula by determining the moles of Carbon (from ) and Hydrogen (from ). We find the molecular formula by comparing the empirical formula mass to the molar mass calculated from the gas density at STP.

Step 1: Find moles of C and H
- Moles of 
- Moles of 
Ratio . Empirical formula is .

Step 2: Calculate molar mass
At STP,  weighs .
Molar mass .

Step 3: Determine molecular formula
Empirical mass of .
. Molecular formula .

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