What volume (mL) of the solvent benzene should be added to 142 mL of the solute CH3CN to generate a solution that is 2.68% by mass CH3CN?
You don't have enough information. You need the density of benzene, the density of CH3CN, and the density of the solution.
Here is the other information..
Molar Mass (g/mol)
CH3CN 41.05
C6H6 78.12
Density (kg/m3):
CH3CN 785.7
C6H6 878.6
Name/Formula:
acetonitrile
CH3CN
benzene
C6H6
I assume this is mass/mass percent.
142 mL CH3CN has what mass? mass=vol x density or mass CH3CN = 142 mL x 0.7857 g/mL = 111.569 grams CH3CN.
What mass solution must we have to equal 2.68%? [111.569 g/mass solution]*100 = 2.68% and solve for g solution. g soln = 299.002 g solution. How much of that is CH3CN and how much benzene.
Total mass = 299.002 g
mass CH3CN = 111.569 g
difference = ??g = mass benzene.
volume benzene = mass benzene/density vol benzene = ?? g benzene/0.8786. I would then round the answer to 3 significant figures.
Post your work if you get stuck. Check my thinking. Check my work.
To find the volume of the solvent benzene that should be added to the solute CH3CN, we need to consider the percentage of CH3CN in the final solution.
Step 1: Convert the given percentage (2.68%) to a decimal fraction by dividing it by 100:
2.68% = 2.68/100 = 0.0268
Step 2: Now, calculate the mass of CH3CN that needs to be present in the solution.
Mass of CH3CN = Percentage by mass × Total mass of the solution
Mass of CH3CN = 0.0268 × Total mass of the solution
Step 3: Subtract the mass of CH3CN from the total mass of the solution to find the mass of the solvent benzene.
Mass of benzene = Total mass of the solution - Mass of CH3CN
Step 4: Finally, use the density of benzene to convert the mass of benzene to volume in mL.
Volume of benzene (mL) = Mass of benzene (g) / Density of benzene (g/mL)
Note: The density of benzene is approximately 0.88 g/mL.
By following these steps, you can calculate the volume of the solvent benzene that should be added to generate the desired solution.