What is the mass in grams of oxygen gas that can be produced from 0.600 grams of KO₂?

Question

The following reaction can be used to convert carbon dioxide to oxygen gas. 4 KO₂ (s) + 2 CO₂(g) → 2 K₂CO₃(s) + 3 O₂(g) What is the mass in grams of oxygen gas that can be produced from 0.600 grams of KO₂?

Answer 1

To jump from grams of KO2 to grams of O2, we will have to follow this path:

Grams KO2 —> moles KO2 —> moles O2 —> grams O2

Step 1: Find the molar mass of KO2 using a periodic table

Molar Mass K: 39.0983 grams/mol

Molar Mass O: 15.999 grams/mol * 2 oxygen atoms in KO2 = 31.998 grams/mol

Molar Mass KO2 = 39.0983 + 31.998 = 71.0963 grams/mol

Step 2: Convert 0.600 grams of KO2 to moles or KO2 using stoichiometry

**Moles turning to anything = multiplying, anything turning into moles = dividing**

0.600 grams KO2 / 71.0963 grams/mol

= 0.00843926… moles KO2

(keep stored in calculator and only round at the very end)

Step 3: Convert from moles KO2 to moles O2 by multiplying by the mole to mole ratio from the given chemical equation

Mole ratio: Coefficient of compound you want / Coefficient of compound you have

Compound we want = O2 coefficient is 3

Compound we have = KO2 coefficient is 4

This converts our number from moles KO2 into moles O2

0.00843926 moles KO2 * 3/4 = 0.00632944 moles O2

(Keep stored in calculator and do not round until the end)

Step 4: Convert from moles of O2 to grams of O2 by using the molar mass from the periodic table

Molar Mass O = 15.999 * 2 atoms of oxygen in O2 = 31.998 grams/mol

*Remember, moles turning into anything else means we multiply!*

0.00632944 moles O2 * 31.998 grams/mol = 0.202529 g O2

Lastly, we will check significant figures and round. The original given number 0.600 grams KO2 had 3 significant digits so we will round our answer to 3.

mass of O2 = 0.203 grams