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

We'll begin by calculating the number of mole in 0.5 g of He.

Mass of He = 0.5 g

Molar mass of He = 4 g/mol

Mole of He =.?Mole of He = 0.125 moleNext, we shall determine the volume occupied by 0.125 mole of He at stp

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

Next, we shall determine the volume of the unknown gas.

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

Next, we shall determine the mole of the unknown gas that occupied 5.6 L at stp.

22.4 L = 1 mole of unknown gas

Therefore,

5.6 L =

5.6 L = 0.25 mole of unknown gas.

Finally, we shall determine the molar mass of the unknown gas.

Mole of unknown gas = 0.25 mole

Mass of unknown gas = 36.5 g

Molar mass of unknown gas =?

= 146 g/mol

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

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Only one reactant yields 2 or more products. meaning you will only have 1 product and it will break down into 2 or more products. eg. h2o -> h2 + o2

It was ernest rutherford