Question

A compound that contains both potassium and oxygen formed when potassium metal was burned in oxygen gas. the mass of the compound was 7.11 grams. The mass of the potassium metal was 3.91 grams. What mass of oxygen was involved in this reaction? Justify your answer.

Answer 1

Answer:
             3.2 g of O₂

Solution:
             This reaction is for the formation of Potassium Superoxide, The reaction is as follow,

                                           K  +  O₂     →     KO₂

First let us confirm that either the given amount of Potassium produces the given amount of Potassium oxide or not,
So,
As,
                39.098 g (1 mole) K produced  =  71.098 g of K₂O
So,
                          3.91 g of K will produce  =  X g of K₂O

Solving for X,
                      X  =  (3.91 g × 71.098 g) ÷ 39.098

                      X  =  7.11 g of K₂O

Hence, it is confirmed that we have selected the right equation,
So,
As,
                     39.098 g of K required  =  32 g of O₂
So,
                     3.91 g of K will require  =  X g of O₂

Solving for X,
                     X  =  (3.91 g × 32 g) ÷ 39.098 g

                     X  =  3.2 g of O₂

Answer 2

The mass of oxygen  that was involved  in the reaction is calculated as below

 mass of the oxygen =mass of the  compound- mass  of the  potassium

that is  7.11 grams -3.91 grams= 3.2  grams  of oxygen  is involved

This is because the mass of the compound composes the mass of potassium + mass of the oxygen