Question #158191

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

2 Â KClO_{3 }Â â†’Â Â 2 KCl + 3 O_{2}

i.Â Â Â Â Â If 1.50 mol of KClO_{3} decomposes, what is the mass of O_{2} that will be produced?

ii.Â Â Â Â Â If 80.0 grams of O_{2} was produced, how many moles of KClO_{3}Â are decomposed?

iii.Â Â Â Â Find the mass ofÂ KClO_{3}Â needed ifÂ we need to produce 2.75Â Â mol of KCl.

Expert's answer

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

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