Potassium chlorate decomposes to form potassium chloride and oxygen gas. If you are trying to make 25 grams of oxygen, how much potassium chlorate will you need to complete your goal?

Question

Please help I am struggling with these chemistry stoichometry problems.

Answer 1

You first need the chemical formulas for the compounds. I won't go over that, but you need to know the principle of charge balance and how nomenclature works.

Then write the balanced chemical equation:

2 KClO₃ --> 2 KCl + 3 O₂

To complete a stoichiometry problem, follow these steps.

(1) Begin your line with the given information: 25 g O₂

(2) At the end of your line, write the units for the result that you want: we want amount of potassium chlorate. This could be moles or grams. I will assume grams.

25 g O₂ = g KClO₃

(3) Use conversion factors to convert the units you are given to the units you want.

-- convert from grams to moles (or vice versa) by using the molar mass of the compound

-- convert from moles to moles using the coefficients in the balanced chemical equation.

-- units that appear in a numerator and a denominator will cancel out. You should cancel out all of the units except for the units that you want to keep.

25 g O₂ * (1 mol O₂ / 32.0 g O₂) * (2 mol KClO₃ / 3 mol O₂) * (122.55 g KClO₃/1 mol) = g KClO₃