A solution of calcium nitrate, Ca(NO3)2, reacts with a solution of ammonium fluoride, NH4F, to form solid calcium fluoride, CaF2, and ammonium nitrate, NH4NO3(aq). When 45.00 mL of 4.8724 x 10-1 M Ca(NO3)2 solution was added to 60.00 mL of 9.9981 x 10-1 M NH4F solution, 1.524 g of CaF2 was isolated.

Question

A solution of calcium nitrate, Ca(NO3)2, reacts with a solution of ammonium fluoride, NH4F, to form solid calcium fluoride, CaF2, and ammonium nitrate, NH4NO3(aq). When 45.00 mL of 4.8724 x 10-1 M Ca(NO3)2 solution was added to 60.00 mL of 9.9981 x 10-1 M NH4F solution, 1.524 g of CaF2 was isolated.

Calculate the number of moles of NH4F originally present

Answer 1

See your post below. You calculate mols to calculate grams.

Answer 2

To calculate the number of moles of NH4F originally present, we need to use the information given in the question.

First, let's determine the number of moles of CaF2 formed. The molecular weight of CaF2 is the sum of the atomic weights of calcium (Ca) and two fluorine atoms (F). The atomic weights of Ca and F are 40.08 g/mol and 18.9984 g/mol, respectively. Therefore, the molecular weight of CaF2 is:

Molecular weight of CaF2 = (1 x 40.08 g/mol) + (2 x 18.9984 g/mol) = 78.0768 g/mol

Given that 1.524 g of CaF2 was isolated, we can calculate the number of moles using the formula:

Number of moles of CaF2 = Mass of CaF2 / Molecular weight of CaF2

Number of moles of CaF2 = 1.524 g / 78.0768 g/mol

Next, we need to determine the stoichiometric ratio between CaF2 and NH4F. From the balanced chemical equation:

Ca(NO3)2 + 2NH4F → CaF2 + 2NH4NO3(aq)

We can see that 1 mole of CaF2 reacts with 2 moles of NH4F. Therefore, the number of moles of NH4F is twice the number of moles of CaF2:

Number of moles of NH4F = 2 x Number of moles of CaF2

Now we can substitute the calculated number of moles of CaF2 into the equation:

Number of moles of NH4F = 2 x (1.524 g / 78.0768 g/mol)

Finally, we need to convert the volume and concentration of the NH4F solution to moles. The volume is given as 60.00 mL and the concentration is 9.9981 x 10-1 M.

First, convert the volume from milliliters to liters:

Volume of NH4F solution = 60.00 mL = 60.00 mL x (1 L / 1000 mL) = 0.06000 L

Then, calculate the number of moles of NH4F using the formula:

Number of moles of NH4F = Volume of NH4F solution x Concentration of NH4F

Number of moles of NH4F = 0.06000 L x 9.9981 x 10-1 M

Now we have the number of moles of NH4F originally present in the solution.