A solution of magnesium chloride, MgCl2, is prepared by dissolving 19.0g of MgCl2 in 250 mL OF water.
a.) Calculate the weight percent of magnesium chloride in solution.
b.)The denstiy of the above solution is 1.05 g/mL. Calculate the molarity of the magnesium chloride solution.
c.)Calculate the ideal freezing point of the solution. (Kf for water=-1.86 C/m)
a. what is 19.0/(250+19); change to percent
b. volumeof solution=mass/density=269/1.05
Molarity=molesMgCl2/volume in liters.
H3po3
To calculate the weight percent of magnesium chloride in the solution, you need to determine the mass of magnesium chloride and the total mass of the solution.
a.) Calculate the weight percent of magnesium chloride in the solution:
1. Convert the volume of water from milliliters (mL) to grams (g) using the density of the solution:
Density = Mass / Volume
Mass = Density x Volume
Mass = 1.05 g/mL x 250 mL = 262.5 g
2. The total mass of the solution is the sum of the mass of the magnesium chloride and the mass of water:
Total Mass = Mass of MgCl2 + Mass of Water
Total Mass = 19.0 g + 262.5 g = 281.5 g
3. Calculate the weight percent of magnesium chloride in the solution:
Weight Percent = (Mass of MgCl2 / Total Mass) x 100
Weight Percent = (19.0 g / 281.5 g) x 100
Weight Percent ≈ 6.75%
b.) To calculate the molarity of the magnesium chloride solution, you need to determine the number of moles of magnesium chloride and the volume of the solution in liters.
1. Calculate the number of moles of magnesium chloride:
Moles of MgCl2 = Mass of MgCl2 / Molar mass of MgCl2
The molar mass of MgCl2 is found by adding the atomic masses of magnesium (Mg) and two chlorine (Cl) atoms:
Mg: 24.31 g/mol
Cl: 35.45 g/mol
Molar mass of MgCl2 = 24.31 g/mol + 2(35.45 g/mol) = 95.21 g/mol
Moles of MgCl2 = 19.0 g / 95.21 g/mol ≈ 0.1995 mol
2. Convert the volume of the solution from milliliters (mL) to liters (L):
Volume = 250 mL x (1 L / 1000 mL) = 0.250 L
3. Calculate the molarity of the magnesium chloride solution:
Molarity (M) = Moles / Volume
Molarity = 0.1995 mol / 0.250 L ≈ 0.798 M
Therefore, the molarity of the magnesium chloride solution is approximately 0.798 M.
c.) To calculate the ideal freezing point of the solution, you can use the equation:
ΔT = Kf * m
where ΔT is the change in temperature (freezing point depression), Kf is the freezing point depression constant, and m is the molality of the solution.
1. Calculate the molality (m) of the solution:
Molality (m) = Moles of solute / Mass of solvent (in kg)
The mass of water can be converted to kilograms by dividing by 1000:
Mass of water = 262.5 g / 1000 = 0.2625 kg
Molality = 0.1995 mol / 0.2625 kg ≈ 0.76 mol/kg
2. Substitute the values into the equation to calculate the freezing point depression (ΔT):
ΔT = -1.86 °C/m * 0.76 mol/kg = -1.415 °C
3. To find the ideal freezing point of the solution, subtract the freezing point depression from the freezing point of pure water (-1.86 °C):
Freezing point = -1.86 °C - (-1.415 °C) = -1.86 °C + 1.415 °C = -0.445 °C
Therefore, the ideal freezing point of the solution is approximately -0.445 °C.