Question

Small quantities of oxygen gas can be generated in the laboratory by heating potassium chlorate according to the reaction below. If 4.74 g of potassium chlorate is heated, what theoretical mass of oxygen gas should be produced?

2KClO_3(s) + 2KCl_(s) à 3O_2(g)

Answer 1

Molar mass of KClO3,

MM = 1*MM(K) + 1*MM(Cl) + 3*MM(O)

= 1*39.1 + 1*35.45 + 3*16.0

= 122.55 g/mol

mass of KClO3 = 4.74 g

mol of KClO3 = (mass)/(molar mass)

= 4.74/122.55

= 0.0387 mol

From balanced chemical reaction, we see that

when 2 mol of KClO3 reacts, 3 mol of O2 is formed

mol of O2 formed = (3/2)* moles of KClO3

= (3/2)*0.0387

= 0.058 mol

mass of O2 = number of mol * molar mass

= 0.058*32

= 1.86 g

Answer: 1.86 g