Small samples of oxygen gas needed in the laboratory can be generated by any number of simple chemical reactions, such as 2 KCl O₃ (s) → 2 KCl (s) + 3 O₂ (g)
What mass of oxygen (in grams) is produced when 122.6 g of KCl O₃ (formula mass = 122.6 amu) takes part in this reaction?

Question

Quizplus · Accepted Answer

According to the balanced equation of the reaction, for every 2 moles of KCl, we get 3 moles of oxygen. From the formula mass of KCl, we know that 122.6 g of KCl is 1 mole. So, for 122.6 g of KCl, we will get (3/2) x 1 mole of oxygen. Using the molar mass of oxygen, we can calculate the mass of oxygen produced. 
(3/2) x 122.6 g / 74.6 g/mol = 48.00 g.
Therefore, the mass of oxygen produced is 48.00 grams, which is option B.

Small Samples of Oxygen Gas Needed in the Laboratory Can