Agas sample contains 4.0 g of ch4 and 2.0 g of he. what is the volume of the sample at stp?

Volume = 16.8 Liters

Explanation:
First, we will need to get the number of moles in the sample as follows:
number of moles = mass / molar mass
number of moles of CH4 = 4 / (12+4) = 4 / 16 = 0.25 moles
number of moles of He = 2 / 4 = 0.5 moles
Total number of moles in the sample = 0.25 + 0.5 = 0.75 moles

Now, at STP, one mole of any gas occupies a volume of 22.4 Liters. To know the volume occupied by 0.75 moles at STP, all we have to do is cross multiplication as follows:
1 mole > 22.4 liters
0.75 moles > ?? liters
Volume = (0.75*22.4) / 1
Volume = 16.8 liters

Hope this helps :)