Question

How many liters of oxygen gas, at standard temperature and pressure, will react with 35.4 grams of calcium metal? Show all of the work used to solve this problem. 2Ca + O2 yields 2CaO

Answer 1

Answer: 19.8 l


Explanation:

1) Chemical equation:

2Ca + O₂ → 2CaO


2) Mole ratios: 2 mol Ca : 1 mol O₂ : 2 mol CaO

3) Convert 35.4 g of Ca to moles:

n = mass in grams / molar mass = 35.4 g / 40.1 g/mol = 0.883 mol

4) Volume proportion: 1 mol of gas at STP = 22.4 l


1 mol at STP              0.883 mol at STP

--------------------- = ------------------------------

22.4 l                                      x

⇒ x = 0.883 mol × 22.4 l / 1 mol = 19.8 l ← answer