A solution is prepared by dissolving 22.8 mL of methanol (d = 0.782 g/mL) in 100 mL of water (d = 1.00 g/mL) so that the final volume of solution is 118 mL. What is the percent methanol by mass?
22.8 mL methanol x 0.782 g/mL = grams methanol.
mass soln = mass methanol + mass H2O
%methanol w/w = (mass methanol/total mass soln)*100 = ??
To find the percent methanol by mass, we need to determine the mass of methanol in the solution and divide it by the total mass of the solution.
Step 1: Calculate the mass of methanol
The mass of methanol can be obtained by multiplying its volume (in mL) by its density (in g/mL).
Mass of methanol = Volume of methanol × Density of methanol
Given:
Volume of methanol = 22.8 mL
Density of methanol = 0.782 g/mL
Mass of methanol = 22.8 mL × 0.782 g/mL
Step 2: Calculate the mass of water
The mass of water can be obtained by multiplying its volume (in mL) by its density (in g/mL).
Mass of water = Volume of water × Density of water
Given:
Volume of water = 100 mL
Density of water = 1.00 g/mL
Mass of water = 100 mL × 1.00 g/mL
Step 3: Calculate the total mass of the solution
The total mass of the solution is the sum of the mass of methanol and the mass of water.
Total mass of the solution = Mass of methanol + Mass of water
Step 4: Calculate the percent methanol by mass
The percent methanol by mass is given by the equation:
Percent methanol by mass = (Mass of methanol / Total mass of the solution) × 100
Now, let's plug in the calculated values:
Mass of methanol = 22.8 mL × 0.782 g/mL
Mass of water = 100 mL × 1.00 g/mL
Total mass of the solution = Mass of methanol + Mass of water
Finally, divide the mass of methanol by the total mass of the solution and multiply by 100 to get the percent methanol by mass.