### 21.
The following reaction produces *H*_{2}*O* gas:

64.0 g of O_2 are used and an excess of

*H*_{2}, and the reaction goes to completion. How many liters of

*H*_{2}*O* gas will be generated if the pressure is 2.0 atm and the temperature is 273 K?

### 31.
The "air" in airbags is generated via the decomposition of solid *NaN*_{3}:

2/3 mole of solid

*NaN*_{3} are completely decomposed at a temperature of 300 K. In order for the final
pressure in the airbag to be 1.2 atm, what must the final volume of the bag be in L? Assume that the Na
takes up no appreciable volume.

*R* = 0.0821.