Hydrogen fluoride is used in the manufacture of Freons (which destroy ozone in the stratosphere) and in the production of aluminum metal. It is prepared by the reaction below.
CaF2 + H2SO4 CaSO4 + 2 HF
In one process 9.00 kg of CaF2 are treated with an excess of H2SO4 and yield 2.76 kg of HF. Calculate the percent yield of HF.
1. Convert 9.00 kg CaF2 to mols. mols = grams/molar mass.
2. Use the coefficients to convert mols CaF2 to mols HF.
3. Convert mols HF to grams. g = mols x molar mass and change to kg. This is the theoretical yield (TE)
4. %yield = (actual yield/TE)*100 = ?
4.
I did that but i have no idea why my answer in wrong ? it should be 93 and i got 45
Chemistry
To calculate the percent yield of HF, you need to compare the actual yield (2.76 kg) to the theoretical yield. The theoretical yield is the amount of HF that would be produced if the reaction went to completion, assuming 100% conversion of CaF2 to HF.
To determine the theoretical yield, you need to calculate the molar mass of CaF2 and HF, and use stoichiometry to convert between moles of CaF2 and moles of HF.
1. Calculate the molar mass of CaF2:
The atomic mass of calcium (Ca) is 40.08 g/mol, and the atomic mass of fluorine (F) is 18.99 g/mol. Since there are two fluorine atoms in CaF2, the molar mass of CaF2 is:
Molar mass of CaF2 = (40.08 g/mol) + (2 * 18.99 g/mol) = 78.05 g/mol
2. Convert the mass of CaF2 to moles:
moles of CaF2 = mass of CaF2 / molar mass of CaF2
moles of CaF2 = 9.00 kg / (78.05 g/mol) = 115.3 mol
3. Use stoichiometry to determine the moles of HF produced:
From the balanced equation, 1 mole of CaF2 produces 2 moles of HF. Therefore, the moles of HF produced is:
moles of HF = 2 * moles of CaF2
moles of HF = 2 * 115.3 mol = 230.6 mol
4. Calculate the theoretical yield of HF in kilograms:
mass of HF = moles of HF * molar mass of HF
The atomic mass of hydrogen (H) is 1.01 g/mol, and the atomic mass of fluorine (F) is 18.99 g/mol. Therefore, the molar mass of HF is:
Molar mass of HF = (1.01 g/mol) + (18.99 g/mol) = 20.00 g/mol
Using this molar mass, the theoretical yield of HF is:
mass of HF = 230.6 mol * (20.00 g/mol) = 4612 g = 4.612 kg
5. Calculate the percent yield:
percent yield = (actual yield / theoretical yield) * 100%
percent yield = (2.76 kg / 4.612 kg) * 100% = 59.9%
Therefore, the percent yield of HF in this process is 59.9%.