Answer:
           a)  2.53 × 10²³ molecules of O₂
           b)  31.90 g of KCl
Explanation:
         The balance chemical equation for given decomposition reaction is as follow;
                  2 KClO₃ → 2 KCl + 3 O₂
Step 1: Calculate Moles for given amount of KClO₃;
          Moles  =  Mass / M.Mass
          Moles  =  34.35 g / 122.55 g/mol
          Moles  =  0.280 moles of KClO₃
Step 2: Find out  moles of O₂ produced;
According to eq,
         2 moles of KClO₃ produces  =  3 moles of O₂
So,
      0.280 moles of KClO₃ will produce  =  X moles of O₂
Solving for X,
          X  =  0.280 mol × 3 mol / 2 mol
           X =  0.42 moles of O₂
Step 3: Calculate No. of Molecules of Oâ‚‚ as,
No. of Molecules  =  Moles × 6.022 × 10²³
No. of Molecules  =  0.42 mol × 6.022 × 10²³ molecules/mol
No. of Molecules  =  2.53 × 10²³ molecules of O₂
Step 1: Calculate Moles for given amount of KClO₃;
          Moles  =  Mass / M.Mass
          Moles  =  52.53 g / 122.55 g/mol
          Moles  =  0.428 moles of KClO₃
Step 2: Find out  moles of KCl produced;
According to eq,
         2 moles of KClO₃ produces  =  2 moles of KCl
So,
      0.428 moles of KClO₃ will produce  =  X moles of KCl
Solving for X,
          X  =  0.428 mol × 2 mol / 2 mol
           X =  0.428 moles of KCl
Step 3: Calculate Mass of KCl as;
             Mass  =  Moles × M.Mass
             Mass  =  0.428 mol × 74.55 g/mol
             Mass  =  31.90 g of KCl
