Question

A sample of pure calcium fluoride with a mass of 15.0 g contains 7.70 g of calcium. How much calcium is contained in 45.0 g of calcium fluoride

Answer 1

To determine the amount of calcium in 45.0 g of calcium fluoride (CaF2), we need to find the fraction of calcium in CaF2 and multiply it by the mass of CaF2. The fraction of calcium in CaF2 is 51.33%, so the mass of calcium in 45.0 g of CaF2 is 23.05 g.

Step-by-step explanation:

To find the amount of calcium contained in 45.0 g of calcium fluoride (CaF2), we need to determine the fraction of calcium in CaF2 and then multiply it by the mass of CaF2.

The molar mass of CaF2 is 78.089 g/mol. To find the fraction of calcium in CaF2, we divide the molar mass of calcium (40.08 g/mol) by the molar mass of CaF2 and multiply by 100 (to convert it to a percentage):

Fraction of calcium in CaF2 = (40.08 g/mol / 78.089 g/mol) x 100% = 51.33%

Now we can calculate the mass of calcium in 45.0 g of CaF2:

Mass of calcium in 45.0 g of CaF2 = (51.33% / 100) x 45.0 g = 23.05 g

Answer 2

23.1 g of Ca

Solution:

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.