Consider an aqueous solution prepared from 250.0 mL of water and 1.27 g of potassium bromide. Express the amount of potassium bromide in this solution in terms of
(a) mass percent
(b) mole fraction
(c) molarity
assume the density of the solution is equal to that of water, 1.00 g mL-1.........help!
Surely you don't want me to work all three. Surely you know SOMETHING about SOME of them. Just remember the definitions:
1. mass percent. grams solute/100 g solution.
2. mole fraction. moles solute/total mules.
3. molarity = moles/L of solution.
Apply those three definitions and you will have your answer(s).
Post your work if you get stuck.
I surely do, and don't call me Shirley! LOL yessss i'm sorry I don't know much about chemistry that's why i'm here!!
1. Mass percent= grams solute/100solution 1.27g/250.0mL = 5.08x10^-03 is my answer but the correct one is 0.505%
2. Mole fraction= moles solute/total moles ?/119.002
3. Molarity 1.27g/119.002= 0.0107moles
than 0.0107/0.25L = 0.048 that's my answer but the correct one is 4.25x10^-2
To express the amount of potassium bromide in the solution in terms of mass percent, mole fraction, and molarity, we can follow these steps:
Step 1: Calculate the mass of the solution
Since the density of the solution is assumed to be equal to that of water (1.00 g/mL), and the volume of water is given as 250.0 mL, we can calculate the mass of the solution.
Mass of solution = density x volume
Mass of solution = 1.00 g/mL x 250.0 mL
Mass of solution = 250.0 g
Step 2: Calculate the amount of potassium bromide
Given that the mass of potassium bromide is 1.27 g, we can use this information to calculate the amount of potassium bromide in the solution.
(a) Mass Percent:
The mass percent is calculated by dividing the mass of the solute by the mass of the solution and multiplying by 100.
Mass percent = (mass of solute / mass of solution) x 100
Mass percent = (1.27 g / 250.0 g) x 100
Mass percent = 0.508% (rounded to three decimal places)
(b) Mole Fraction:
The mole fraction is the ratio of the moles of the solute to the total moles in the solution.
To calculate the moles of potassium bromide, we need the molar mass of KBr, which is approximately 119 g/mol.
Moles of KBr = mass of KBr / molar mass of KBr
Moles of KBr = 1.27 g / 119 g/mol
Moles of KBr = 0.0107 mol (rounded to four decimal places)
To calculate the mole fraction, we need to find the total moles in the solution. Since water is the solvent, we assume it is in excess and neglect its contribution to the total mole fraction.
Mole fraction of KBr = moles of KBr / moles of KBr
Mole fraction of KBr = 0.0107 mol / 0.0107 mol
Mole fraction of KBr = 1.000 (rounded to three decimal places)
(c) Molarity:
Molarity is the ratio of the moles of solute to the volume of the solution in liters.
To calculate the molarity, we need to convert the volume of water to liters.
Volume of water = 250.0 mL = 0.2500 L
Molarity of KBr = moles of KBr / volume of solution
Molarity of KBr = 0.0107 mol / 0.2500 L
Molarity of KBr = 0.0428 M (rounded to four decimal places)
So, the amount of potassium bromide in this solution is:
(a) 0.508% (mass percent)
(b) 1.000 (mole fraction)
(c) 0.0428 M (molarity)