Student A prepared a solution by dissolving 8.00 g potassium perchlorate in 72.0 g H2O. Given that the density of potassium perchlorate solution is 2.524 g/mL at 25 degree C .
(a) Calculate the % by mass of solute of the potassium perchlorate solution.
(b) Calculate the mass/volume percent of the potassium perchlorate solution.
(c) Calculate the molar concentration of the potassium perchlorate solution.
(d) Calculate the mole fraction of the solvent.
(e) Calculate the molality of the potassium perchlorate solution.
(a) Calculate the % by mass of solute of the potassium perchlorate solution.
% w/w (or m/m) = (mass solute/mass solution)*100
mass solute = 8 g
mass solvent = 72 g
mass solution = 80 g
% w/w = (8/80)*100 = ?
(b) Calculate the mass/volume percent of the potassium perchlorate solution.
% (w/v)*100 or %(m/v) = ?
mass solution = 80 g
volume of solution = mass/density = 80/2.524 = ?
% m/v = ?
(c) Calculate the molar concentration of the potassium perchlorate solution.
M = #mols/L solution.
mols KClO4 = grams/molar mass = 8/molar mass = ?
You have mols and volume (volume from part b), solve for M.
d) Calculate the mole fraction of the solvent.
mols KClO4 you have from part c.
mols H2O = grams H2O/molar mass H2O = 72/18 = ?
Total mols = mols KClO4 + mols H2O = ?
Then mols solvent (H2O) = mols H2O/total mols = ?
(e) Calculate the molality of the potassium perchlorate solution.
m = mols KClO4/kg solvent
mols KClO4 you have from above in one of the othr parts.
kg solvent. 72 g H2O = 0.072 kg.
Solve for m.
Post your work if you get stuck.
In order to answer these questions, we first need to understand the formulas and concepts related to each calculation. Let's go through each question one by one and explain how to find the answers.
(a) To calculate the % by mass of solute of the potassium perchlorate solution, we need to divide the mass of the solute (potassium perchlorate) by the total mass of the solution and multiply by 100.
The mass of the solute can be calculated by subtracting the mass of the solvent (water) from the total mass of the solution:
Mass of solute = Total mass of solution - Mass of solvent.
In this case, the mass of the solute is given as 8.00 g and the mass of the solvent (water) is given as 72.0 g. Therefore, we can calculate the total mass of the solution as the sum of the mass of the solute and the mass of the solvent.
Total mass of solution = Mass of solute + Mass of solvent.
Finally, we can plug in these values into the formula to find the % by mass of solute:
% by mass of solute = (Mass of solute / Total mass of solution) x 100.
(b) To calculate the mass/volume percent of the potassium perchlorate solution, we need to divide the mass of the solute by the volume of the solution and multiply by 100.
The volume of the solution can be calculated using the density of the solution and the mass of the solution:
Volume of solution = Mass of solution / Density of solution.
Once we have the volume of the solution, we can calculate the mass/volume percent using the formula:
Mass/volume percent = (Mass of solute / Volume of solution) x 100.
(c) To calculate the molar concentration of the potassium perchlorate solution, we need to divide the moles of the solute by the volume of the solution in liters.
To find the moles of the solute, we divide the mass of the solute by its molar mass. The molar mass of potassium perchlorate (KClO4) can be found by adding up the atomic masses of its constituent elements.
Once we have the moles of the solute, we can calculate the molar concentration using the formula:
Molar concentration = Moles of solute / Volume of solution (in L).
(d) To calculate the mole fraction of the solvent, we divide the moles of the solvent by the total moles of all components in the solution.
To find the moles of the solvent, we divide the mass of the solvent by its molar mass. Similar to the previous question, the molar mass of water (H2O) can be found by adding up the atomic masses of hydrogen and oxygen.
To find the total moles of all components in the solution, we need to divide the total mass of the solution by its molar mass. The molar mass of the solution can be calculated by summing the products of the molar mass of each component (solute and solvent) with their respective mole fractions.
Finally, we can calculate the mole fraction of the solvent using the formula:
Mole fraction of solvent = Moles of solvent / Total moles of all components.
(e) To calculate the molality of the potassium perchlorate solution, we need to divide the moles of the solute by the mass of the solvent (in kg).
Similar to the previous questions, we need to find the moles of the solute by dividing its mass by its molar mass. Then, we divide the mass of the solvent by 1000 to convert it to kilograms.
Once we have the moles of the solute and the mass of the solvent in kilograms, we can calculate the molality using the formula:
Molality = Moles of solute / Mass of solvent (in kg).