Calculate the molality (m) of a 6.56 kg sample of a solution of the solute acetone dissolved in the solvent ethanol if the sample contains 1.44 kg of acetone.
Additional info:
Molar Mass (g/mol)
acetone = 58.05
ethanol = 46.07
Density (g/mL)
acetone = 0.7899
ethanol = 0.7893
Dr. Bob, I asked a question like this about molality and the step by step explanation that you provided helped greatly. Could you please help me out with this one. It is slightly different and I'm really confused. Thank you!
never mind, I figured it out. I'll post the explanation just in case anyone else needs help with a similar problem.
Equation:
molality acetone = mol acetone/kg ethanol
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to find kg ethanol:
total mass - sample mass of acetone
(6.56kg - 1.44kg) = 5.12kg ethanol
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to find mol acetone:
convert kg to g of sample mass given
(1.44kg x 1000g/kg) = 1440g acetone
divide sample mass(grams) by molar mass
(1440g / 58.05g)= 24.80620155mol acetone
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Plug in answers to formula:
Molality = 24.80620155 mol acetone/ 5.12kg ethanol
I didn't go through the math but this looks ok to me.
Of course! I'd be happy to help you with this problem.
To calculate the molality (m) of a solution, we need to use the following formula:
m = (moles of solute) / (mass of solvent in kg)
To begin, we need to find the moles of acetone and the mass of ethanol.
Step 1: Convert the mass of acetone from kg to grams.
1.44 kg * 1000 g/kg = 1440 g
Step 2: Calculate the moles of acetone using its molar mass.
moles of acetone = mass of acetone / molar mass of acetone
moles of acetone = 1440 g / 58.05 g/mol = 24.82 mol
Step 3: Convert the mass of ethanol from kg to grams.
6.56 kg * 1000 g/kg = 6560 g
Step 4: Convert the mass of ethanol from grams to milliliters (since density is given in g/mL).
ethanol volume = mass of ethanol / density of ethanol
ethanol volume = 6560 g / 0.7893 g/mL = 8317.74 mL
Step 5: Convert the volume of ethanol from milliliters to liters.
ethanol volume = 8317.74 mL * (1 L / 1000 mL) = 8.31774 L
Step 6: Convert the volume of ethanol from liters to kilograms.
mass of ethanol = ethanol volume * density of ethanol
mass of ethanol = 8.31774 L * 0.7893 g/mL = 6.556 kg
Now that we have the moles of acetone (24.82 mol) and the mass of ethanol (6.556 kg), we can calculate the molality.
m = (moles of solute) / (mass of solvent in kg)
m = 24.82 mol / 6.556 kg ≈ 3.79 mol/kg
Therefore, the molality (m) of the solution is approximately 3.79 mol/kg.