# an unknown hydrocarbon gas sample has a volume of 500.0 mL and a mass of 0.3569 grams at STP.  what is the molar mass of the gas? I need the formula too!

Mole mass of C = 12 g/mol

mole mass of H = 1g/mol

Lets assume that we have n moles of the hydrocarbon.

At STP the molic mass of a gas = 22.4L

So the gas moles in 500ml       = 1/22.4*0.5

= 0.0223 mol

Lets assume the...

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Mole mass of C = 12 g/mol

mole mass of H = 1g/mol

Lets assume that we have n moles of the hydrocarbon.

At STP the molic mass of a gas = 22.4L

So the gas moles in 500ml       = 1/22.4*0.5

= 0.0223 mol

Lets assume the mole mass of hydrocarbon is M.

Then 0.3569/M = 0.0223-------->M = 16

So the molic mass of the hydrocarbon is 16 g/mol.

It is obvious that w cannot have more than one C since the mole mass is 16. Then the rest is H.

So the hydrocarbon is CH_4

Assumption

Here we have to assume that the gas of the hydrocarbon shows ideal gas behavior.

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