23.1 g of Ca
It is a simple proportional problem in which we will find either the increased or decreased value of calcium with proportional to Calcium fluoride.
Therefore as given,
15.0 g of pure CaF₂ contains = 7.70 g of Ca
So,
45.0 g of pure CaF₂ will contain = X g of Ca
Solving for X,
X = (45.0 g × 7.70 g) ÷ 15.0 g
X = 23.1 g of Ca
Hence, as the amount of CaF₂ has increased from 15.0 g to 45.0 g therefore, the amount of Ca it contained also increased from 7.70 g to 23.1 g.
