The mole fraction of an aqueous solution of potassium perchlorate is 0.125. Assuming that the density of this solution is 1.20g mL-1, calculate the following:
(A) the mass percent of potassium perchlorate in the solution.
(B) the molarity of potassium perchlorate in the solution.
mole fraction KClO4 = 0.125 and mole fraction water = 0.875. If we take enough sample to have 1.00 total mol soln, we will have 0.125 moles KClO4 or 0.125 x molar mass KClO4 in grams. 0.875 moles H2O = 0.875 x molar mass water = grams water.
grams soln = grams water + grams KClO4.
mass % w/w = (mass KClO4 in grams/mass soln)*100
b)Convert g KClO4 (in previous problem) to moles. moles = grams/molar mass.
Use the density to convert g soln to L. Then M = moles/L of soln.
Post your work if you get stuck.
Ok I got (A) to work out for me 52.4%
but i'm stuck on (B)
moles= grams/molar mass
1.20g/138.547= 8.66x10^-3 ( this cant be right)
then M = moles/L 8.66x10^-3/1.2x10^-3= 7.22
I got 7.22 but the right answer is 4.53M
To calculate the mass percent of potassium perchlorate in the solution, we need to find the mass of potassium perchlorate and the total mass of the solution.
Let's assume we have 100 g of the aqueous solution. The mass fraction of potassium perchlorate in the solution is 0.125, which means that 0.125 x 100 g = 12.5 g of the solution is potassium perchlorate.
Therefore, the mass percent of potassium perchlorate in the solution is (mass of potassium perchlorate / total mass of solution) x 100% = (12.5 g / 100 g) x 100% = 12.5%.
To calculate the molarity of potassium perchlorate in the solution, we first need to find the number of moles of potassium perchlorate.
The molar mass of potassium perchlorate (KClO4) can be calculated by adding up the atomic masses of the elements: K (39.10 g/mol) + Cl (35.45 g/mol) + 4O (4 x 16.00 g/mol) = 138.55 g/mol.
Using the formula weight = mass / molar mass, we can find the number of moles of potassium perchlorate in the solution:
moles of potassium perchlorate = mass of potassium perchlorate / molar mass of potassium perchlorate = 12.5 g / 138.55 g/mol = 0.0900 mol.
The molarity (M) is defined as moles of solute per liter of solution. Since the density of the solution is given as 1.20 g/mL, we can calculate the volume of the solution using V = mass / density = 100 g / 1.20 g/mL = 83.33 mL.
Converting mL to L: 83.33 mL x (1 L / 1000 mL) = 0.0833 L.
Finally, we can calculate the molarity:
Molarity of potassium perchlorate = moles of potassium perchlorate / volume of solution in liters = 0.0900 mol / 0.0833 L ≈ 1.08 M.
So, the mass percent of potassium perchlorate in the solution is 12.5% and the molarity of potassium perchlorate in the solution is approximately 1.08 M.