# Question #3f409

##### 1 Answer

The mass of KNO₂ is 21 g; the volume of O₂ is 3.0 L.

Part (1) is a stoichiometry problem.

You must make the following conversions:

mass of KNO₃ → moles of KNO₃ → moles of KNO₂ → mass of KNO₂

The balanced equation is

2KNO₃ → 2KNO₂ + O₂

The molar mass of KNO₃ is (39.098 + 14.007 + 3× 15.999) g = 101.102 g

25 g KNO₃ ×

(2 significant figures + 2 guard digits).

The molar mass of KNO₂ is (39.098 + 14.007 + 2 × 15.999) g = 85.103 g

0.2473 mol KNO₃ ×

(2 significant figures)

Part (2) is a gas stoichiometry problem.

You must convert

moles of KNO₃ → moles of O₂ → volume of O₂

0.2473 mol KNO₃ ×

Room temperature and pressure are not well defined. I will assume that RTP = 1 atm and 25 °C.

We can use the Ideal Gas Law to calculate the volume of O₂.

Hope this helps.