Calculate the molality of methanol in a solution prepared by dissolving 75.0 mL of methanol, CH3OH (d = 0.791 g/mL), in 150 g of ethanol, C2H5OH.
75mL*.791g/mL= 59.325g
59.325g/32g/mol=1.854moles
1.854moles/.150kg=12.36m
The definition is M = mols/kg solvent
Well, well, well! Looks like we're mixing some party drinks here! Now, to calculate the molality, we need to know the moles of solute (methanol) and the mass of the solvent (ethanol). Let's break it down!
First, we need to find the moles of methanol. To do that, we need to know the mass of methanol:
Mass of methanol = Volume of methanol x Density of methanol
= 75.0 mL x 0.791 g/mL
= 59.325 g
Next, we calculate the moles of methanol using its molar mass, which is 32.04 g/mol:
Moles of methanol = Mass of methanol / Molar mass of methanol
= 59.325 g / 32.04 g/mol
≈ 1.849 mol
Now let's look at the mass of the solvent, which is given as 150 g of ethanol. No calculations needed there!
Finally, we can calculate the molality:
Molality = Moles of solute / Mass of solvent (in kg)
= 1.849 mol / 0.150 kg
≈ 12.326 mol/kg
So, the molality of methanol in the solution is approximately 12.326 mol/kg. Cheers to that, my friend!
To calculate the molality of methanol in the solution, we need to know the number of moles of methanol and the mass of the solvent (ethanol). We can follow these steps:
1. Calculate the mass of methanol:
Given volume of methanol = 75.0 mL
Density of methanol, CH3OH = 0.791 g/mL
Mass of methanol = Volume × Density = 75.0 mL × 0.791 g/mL = 59.325 g
2. Calculate the moles of methanol:
Molar mass of CH3OH = 12.01 g/mol (for carbon) + 1.01 g/mol (for each hydrogen) + 16.00 g/mol (for oxygen) = 32.04 g/mol
Moles of methanol = Mass of methanol / Molar mass = 59.325 g / 32.04 g/mol = 1.851 mol
3. Calculate the mass of the solvent (ethanol):
Given mass of ethanol = 150 g
4. Convert the mass of ethanol to kg:
Mass of ethanol = 150 g = 0.150 kg (since 1 kg = 1000 g)
5. Calculate the molality:
Molality (m) = Moles of solute / Mass of solvent in kg
Molality of CH3OH = 1.851 mol / 0.150 kg = 12.34 mol/kg (rounded to two decimal places)
Therefore, the molality of methanol in the solution is 12.34 mol/kg.
My calculation
0.791g/ml x 75ml /46 g/mol = 1.29M
1.29M /0.15KG
x= 0.116M