1. How many mL of acetone are needed to prepare a 10% v/v solution in 500 mL of methanol?
2. If a 500mL solution of n-propanol in water is prepared with 4mL of alcohol, what is the concentration of alcohol in % v/v?
I've never worked with %v/v before so I'm not sure if I worked the problems correctly but for the first one I got 50mL of acetone and for the second one I got that it would be 0.8%v/v.
correct, and correct.
thank you!
I think #1 needs more work.
%v/v = [(mL solute/mL SOLUTION)]*100 = ?
50 mL acetone + 500 mL methanol is more than 500 mL total volume.
Assuming the volumes are additive (probably they are not), then
[(50/550)]*100 = 9.1%
To calculate the required amount of acetone in the first problem and the concentration of alcohol in the second problem, we need to understand the concept of percent volume by volume (% v/v) and how to use it in calculations.
1. Calculation for the amount of acetone needed:
The term "10% v/v solution" means that the volume of solute (acetone) is 10% of the total volume of the solution. Here's how you can calculate the amount of acetone needed:
Step 1: Convert the given percentage (10%) into a decimal fraction: 10% = 0.10.
Step 2: Multiply the fraction obtained in step 1 by the total volume of the solution (500 mL): 0.10 x 500 mL = 50 mL.
So, you are correct. To prepare a 10% v/v solution of acetone in 500 mL of methanol, you would need 50 mL of acetone.
2. Calculation for the concentration of alcohol:
The concentration is expressed as a percentage of the volume of solute (alcohol) in the total volume of the solution (n-propanol + water). Let's calculate the concentration:
Step 1: Divide the volume of alcohol (4 mL) by the total volume of the solution (500 mL): 4 mL / 500 mL = 0.008.
Step 2: Multiply the fraction obtained in step 1 by 100 to get the percentage: 0.008 x 100 = 0.8%.
So, you are correct again. The concentration of alcohol in the n-propanol and water solution would be 0.8% v/v.
Remember, % v/v represents the volume of solute (in mL) per 100 mL of the total solution volume.