what is the relative mass of methane?

Question

how many moles of methane are there in 4 g of pure methane? haw many moles of oxygen are there in 7 dm3

Answer 1

Methane, CH4, MW = 16g/mol
moles of 4g of CH4: 4g / 16g/mol = 0.25mol

At STP, moles of oxygen in 7dm3 is...
n = PV/RT = 1 atm * 7 L / 0.08206 L-atm/molK * 298 K
n = 0.286 mol

Answer 2

methane: CH4

Mr;
carbon 12
hydrogen 1

Mr of methane= 1*carbon+4*hydogen
=12+4
=16

therefore one mole of methane weighs 16 grams

4 g of methane= 4/16
=0.25 moles
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one mole of any gas occupies 24 dm3 at r.t.p

moles of oxygen in 7 dm3= 7/24
=0.292 moles

Answer 3

yep, CH4 = 16 g per mole

but any gas occupies 22.4 dm3 (NOT 24!) at STP, so there are 7/22.4 = 0.312 moles of O2 in 7 dm3