A 0.500 g sample of He at STP has a volume that is one-half that of an unknown pure gas also at STP. The unknown pure gas sample has a mass of 36.5 g. What is the molar mass of the unknown gas?

The molar mass of the unknown gas which has a mass of 36.5 g is 146 g/mol

Mass of He = 0.5 g

Molar mass of He = 4 g/mol

At standard temperature and pressure (stp),

1 mole of He = 22.4 L

Therefore,

0.125 mole of He = 0.125 × 22.4

0.125 mole of He = 2.8 L

Volume of He = 2.8 L

Volume of unknown gas =?

Volume of He = ½ × Volume of unknown gas

2.8 = ½ × Volume of unknown gas

Cross multiply

Volume of unknown gas = 2.8 × 2

Volume of unknown gas = 5.6 L

22.4 L = 1 mole of unknown gas

Therefore,

5.6 L =

5.6 L = 0.25 mole of unknown gas.

Mole of unknown gas = 0.25 mole

Mass of unknown gas = 36.5 g

Molar mass of unknown gas =?

Therefore, the molar mass of the unknown gas is 146 g/mol

Learn more: link

hurricanes form in warm water

because natural gas is colorless, odorless, and tasteless, distributors add mercaptan (a chemical that smells like sulfur) to give natural gas a distinct unpleasant odor (it smells like rotten eggs). they locate the types of rock that are likely to contain natural gas deposits.