2.3 moles CaCO₃
That is;
CaCO₃(s) → CaO(s) +CO₂(g)
From the question, 129 grams of CaO were formed
We are required to calculate the number of moles of CaO used.
This can be done in the following steps;
Step 1: Moles of CaO produced
The number of moles is calculated by dividing mass by the molar mass of a compound.
Molar mass of CaO is 56.0774 g/mol
Therefore;
Moles of CaO = 129 g ÷ 56.0774 g/mol
= 2.3 moles
Step 2: Moles of CaCO₃ decomposed
From the equation 1 mole of CaCO₃ decomposes to yield 1 mole of CaO
Therefore;
For 2.3 moles of CaO to be produced then 2.3 moles of CaCO₃ would be decomposed.
Therefore;
The moles of CaCO₃ decomposed is 2.3 moles