2NaClO3 ——> 2NaCl + 3O2 1) if you produced 114.25g NaCl, how many grams of NaClO3 did you decompose?

2) Using the same reaction in the first exercise; how many particles of NaClO3 are needed to
produce 68.30L of oxygen?

Find moles of Known Substance (NaCl)

Moles of NaCl = mass ÷ molar mass

                        =  114.25 g ÷ 58.44 g/mol

                        = 1.955 mol

Use Mole Ratio of Known to Unknown (NaCl : NaClO₃) to Determine Moles of Unknown

The mole ratio of NaCl to NaClO₃ is 2 to 2 or simply 1 to 1.

This means that for each mole of NaCl produced the same number of moles of NaClO₃ was decomposed.

∴ since moles of NaCl = 1.955 mol,

then moles of NaClO₃ = 1.955 mol

Find Mass of Unknown

Mass of NaClO₃ = moles × molar mass

                           = 1.955 mol × 106.44 g/mol

                           =  208.09 g

Determine the Moles of Known (O₂)

moles of O₂ = (volume × density) ÷ molar mass

                    = (68.30 L × 0.0828 g/L) ÷ 32 g/mol

                    = 0.177 mol

Use Mole Ratio of Known to Unknown (O₂ : NaClO₃) to Determine Moles of Unknown

Mole ratio of O₂ : NaClO₃ is 3 : 2. Therefore for each mole of oxygen produced, ²/₃ the moles of NaClO₃ is produced.

∴ if moles of O₂  =  0.177 mol

then moles of NaClO₃ =  0.177 mol × ²/₃

                                     = 0.118 mol

Find the Number of Particles of Unknown

Number of particles  = moles × Avogadro's Number

                                  = 0.118 mol × (6.022 × 10²³ particles/mol)

                                  =  7.11 × 10²² particles