Question

b)  Answer the following stoichiometry questions by referring to the equation below:

2       

KClO₃               2 KCl + 3 O₂

i.        If 1.50 mol of KClO₃ decomposes, what is the mass of O₂ that will be produced? 

Answer 1

This is a problem of determining mole ratios in the stoichiometric equations.

(i) Mass of O2

We have moles of KClO3 = 1.50mol

Mole ratios of KClO3 : O2 = 2:3

Thus moles of O2 $=\dfrac{3}{2}x1.50mol$

= 2.25mol of O2

Moles $=\dfrac{Mass}{MM}$

Therefore Mass of O2 = Moles x MM

= 2.25mol x 32g/mol

= 72g

(ii) Moles of KClO3

Moles of O2 $=\dfrac{mass}{MM} = \dfrac{80g}{32g/mol} = 2.5mol$

Mole ratios of O2:KClO3 = 3:2

Moles of KClO3 $=\dfrac{2}{3}x 2.5mol = 1.67 mol$

(ii)Mass of KClO3

We are given moles of KCl = 2.75mol

Mole ratios of KCl : KClO3 = 2:2

Thus moles of KClO3 $=\dfrac{2}{2}x2.75mol = 2.75 mol$

Mass = Moles x MM

= 2.75mol x 122.55g/mol

= 337.013g