[kinerd]

Natural gas is a mixture of hydrocarbons, primarily methane (CH₄) and ethane (C₂H6).  A typical mixture might have Χmethane = 0.915 and Χethane = 0.085.
a. What are the partial pressures of the two gases in a 15.00-L container of natural gas at 20.°C and 1.44 atm?
b. Assuming complete combustion of both gases in the natural gas sample, what is the total mass of water formed?

I found the answer to Part A by multiplying the total pressure (1.44 atm) by the mole fractions to get 1.32 atm for methane and 0.12 atm for ethane.

I'm not sure how to answer Part B. I tried writing an equation:
CH₄ + C₂H₆ + O₂ CO₂ + H₂O
but i couldn't balance it correctly. Do I need to split into two equations? What would I do after that?

Thanks!

[UG]

Hi kinerd,
For (b), you need to rearrange the ideal gas equation so that you can find 'n', the amount of substance. You have the partial pressures of methane and ethane so you can find how many moles of each there are. Then the number of moles of water formed from the combustion of each gas can be found (best to write a balanced combustion reaction for each gas), add them up and then find the mass of water.

[kinerd]

Great! Thanks for explaining so clearly.