How can i find the theoretical yield?

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.  

1. they vary with a higher number because boiling is way hotter than melting