Answer:
 Mass = 15.20 g of KCl
Step-by-step explanation:
 The balance chemical equation for the decomposition of KClO₃ is as follow;
 2 KClO₃ = 2 KCl + 3 O₂
Step 1: Calculate moles of KClO₃ as;
Moles = Mass / M/Mass
Moles = 25.0 g / 122.55 g/mol
Moles = 0.204 moles
Step 2: Find moles of KCl as;
According to equation,
 2 moles of KClO₃ produces = 2 moles of KCl
So,
 0.204 moles of KClO₃ will produce = X moles of KCl
Solving for X,
 X = 2 mol × 0.204 mol / 2 mol
 X = 0.204 mol of KCl
Step 3: Calculate mass of KCl as,
Mass = Moles × M.Mass
Mass = 0.204 mol × 74.55 g/mol
Mass = 15.20 g of KCl