A sample of calcium fluoride with a mass of 15.0 g contains 8.40 g of calcium. Assuming that the sample is pure calcium fluoride, how much calcium would be present in a 30.0 g sample?

My answer: 16.8 g Ca

Based on your answer and applying what you know about calcium fluoride, is the 15.0 g sample actually pure calcium fluoride? Explain why or why not. Start with a molecular mass calculation to support your answer.

My molecular mass calculation:
mass of CaF2= (40.08)+(2)(19)= 78.08 g CaF2

I don't know where to go from here.

CaF2 molar mass = 78.07 check

Ca molar mass = 40.1
F2 molar mass = 2*19 = 38

8.4 g calcium is 8.4/40.1 = .2095 mol

.2095 mol of CaF2 = 16.35 grams, not 15 grams

now part a
30 g * 40.1/78.07 = 15.3

To determine if the 15.0 g sample is pure calcium fluoride, we can compare the amount of calcium present in the sample with the expected amount based on the molecular mass calculation.

First, we need to calculate the molar mass of calcium fluoride (CaF2) using the atomic masses of calcium (Ca) and fluorine (F).

Molar mass of CaF2 = (mass of Ca) + (2 * mass of F)
= 40.08 g/mol + (2 * 19.00 g/mol)
= 40.08 g/mol + 38.00 g/mol
= 78.08 g/mol

Now, using the molar mass and the given mass of calcium in the 15.0 g sample (8.40 g), we can determine the expected amount of calcium present in the sample.

Expected amount of calcium in the 15.0 g sample = (mass of calcium / mass of sample) * molar mass of CaF2
= (8.40 g / 15.0 g) * 78.08 g/mol
= 0.56 * 78.08 g/mol
= 43.81 g

Since the expected amount of calcium in the 15.0 g sample is 43.81 g, but the actual amount given is only 8.40 g, we can conclude that the sample is not pure calcium fluoride.

To determine whether the 15.0 g sample of calcium fluoride is actually pure, you can compare the expected amount of calcium in the sample (based on its molecular mass) with the amount of calcium found in the sample.

Based on your molecular mass calculation, 1 mole of calcium fluoride (CaF2) has a mass of 78.08 g. And since there is 1 mole of calcium (Ca) in 1 mole of calcium fluoride, the molar mass of calcium is 40.08 g/mole.

To find the expected amount of calcium in the 15.0 g sample, you can use the mass percent composition of calcium in calcium fluoride. The mass percent composition of calcium is calculated by dividing the mass of calcium by the mass of calcium fluoride and multiplying by 100%.

mass percent composition of calcium in CaF2 = (mass of Ca / mass of CaF2) * 100%

= (8.40 g / 15.0 g) * 100%

= 56%

So, according to the expected mass percent composition, a 15.0 g sample of pure calcium fluoride should contain 56% calcium. However, the sample contains only 8.40 g calcium, which is less than the expected amount.

Therefore, based on the comparison between the expected and actual amounts of calcium, we can conclude that the 15.0 g sample is not pure calcium fluoride.