We have the masses of two reactants, so this is a limiting reactant problem.
We know that we will need a balanced equation with masses and molar masses of the compounds involved.
Step 1. Gather all the information in one place with molar masses above the formulas and masses below them.
M_r: 110.98 105.99 100.09
CaCl₂ + Na₂CO₃ ⟶ CaCO₃ + 2NaCl
Mass/g: x y
Step 2. Calculate the moles of each reactant
Moles of CaCl₂ = x g CaCl₂ × (1 mol CaCl₂/110.98 g CaCl₂)
= (x/110.98) mol CaCl₂
Moles of Na₂CO₃ = y g Na₂CO₃ × (1 mol Na₂CO₃/105.99 g Na₂CO₃)
= (y/105.99) mol Na₂CO₃
Step 3. Identify the limiting reactant
Calculate the moles of CaCO₃ we can obtain from each reactant.
From CaCl₂ :Moles of CaCO₃
= (x/110.98) mol CaCl₂ × (1 mol CaCO₃/1 mol CaCl₂) = (x/110.98) mol CaCO₃
From Na₂CO₃: Moles of CaCO₃
= (y/105.99) mol Na₂CO₃ × (1 mol CaCO₃/1 mol Na₂CO₃) = (y/105.99) mol CaCO₃
The limiting reactant is the one that gives the smaller amount of CaCO₃.
Step 4. Calculate the theoretical yield of CaCO₃ that you can obtain from the limiting reactant.
