Question

How many grams of potassium chloride are produced if 25 g of potassium chlorate decompose in the reaction `2KClO_3 -> 2KCl + 3O_2`?

Answer 1

15.2 g of KCl would be produced

Explanation:

The general pattern for solving these types of problems is

1. Find "moles" of the known substance
2. Write down the mole ratio using the coefficients from the balanced equation
3. rearrange to solve for the moles "unknown"
4. Convert moles "unknown" to required units (i.e. mass, volume, concentration)

So to solve the problem:

1. Molecular mass of `KClO_3` = 39.10 + 35.45 + 3(16.00)
   = 122.55

2. Moles of `KClO_3` = `25/122.55` = 0.204 mol

3. mol ratio: `mol KCl // mol KClO_3` = `2/2`
   so
   mol of KCl = `2/2 xx mol KClO_3`

   mol of KCl = `2/2 xx 0.204`

   mol of KCl = 0.204 mol

4.. molecular mass of KCl = 39.10 + 35.45 = 74.55
mass KCl = `0.204 xx 74.55` = 15.208 g

Therefore 15.2 g of KCl would be formed.