Single Choice

The density of a gas is $$1.78 \ g \ L^{-1}$$ at STP. The weight of one mole of gas is:

A$$39.9\ g$$
Correct Answer
B$$22.4\ g$$
C$$3.56\ g$$
D$$29\ g$$

Solution

Density $$=1.78 \ g L^{−1}$$ at STP

mass of $$1\ L$$ gas$$=1.78\ g$$

1 mol of gas at STP $$=22.4\ L$$

$$\therefore\ $$mass of $$22.4\ L$$ gas$$=22.4 \times 1.78=39.872\ g$$

Option $$A$$ is correct.

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