chemistry class

Question

How many molecules of O2 are produced when 28.9 g of KClO3 decomposes as shown in the reaction?

2KClO3⟶2KCl+3O2

Answer 1

Step 1: Is our equation balanced?

Yes. We are good here, but always check to make sure you don't need to balance your equation first

Step 2: Game Plan - What am I given and what do I need to know?

We are given 28.9g of KClO₃.and we want to get to grams of O₂. Our game plan will look like this:

grams of KClO₃ → (use molar mass of KCLO₃) → moles of KCLO₃ → (use mole to mole ratio of KCLO₃ to O2) → moles of O² → ( use Avogadro's number) → molecules of O₂

Step 3: Find molar mass of KCLO3 and the mole to mole ratio of KCLO₃ to O₂

Molar mass of KCLO₃ = We get this by adding the atomic weights of all the elements in our compound. Remember to multiply any atomic weights by subscripts if needed.

atomic weight of K = 39.098

atomic weight of Cl = 35.45

atomic weight of O = 16 (3) = 48

39.098 + 35.45 + 48 = 122.55 g = molar mass of KCLO₃

Mole to mole ratio of KCLO3 to O2: We get this by looking at the coefficients in our balanced equation.

2KClO₃ ⟶ 2KC l+ 3O₂ For every 2 moles of KCLO₃, 3 moles of O₂ are formed.

Now we have everything we need to solve our problem.

Step 4 Solve.

28.9 g KCLO₃ × 1 mol KCLO₃ × 3 mol O₂ × 6.022 × 10²³ molecules of O₂

122.5 g KCLO₃ 1 mol KCLO₃ 1 mol O₂

2.13×10²³ molecules of O2 produced