Arthur is performing a lab which requires a 0.2 M solution of calcium hydroxide. However, the only calcium hydroxide solution available has a concentration of 0.5 M. How can Arthur dilute the 0.5 M solution to make 10 mL of a 0.2 M solution?
A.He needs to add 2.5 mL of the 0.5 M solution to 10 mL of water.
B.He needs to add 4 mL of the 0.5 M solution to 10 mL of water.
C.He needs to add 4 mL of the 0.5 M solution to 6 mL of water.
D.He needs to add 2.5 mL of the 0.5 M solution to 7.5 mL of water.
A. he needs to add 4 mL of the 0.5 M solution to 6 mL of water.
The correct answer is not listed but the answer you're supposed to pick is c. The reason it isn't the correct answer is because you're assuming the 4mL adds to the 6 mL to make 10.0 mL solution. BUT solutions are not additive. c should say it this way. "He needs to add 4 mL of the 0.5 M solution to a container and add enough water to make 10.0 mL of solution."
To dilute the 0.5 M solution of calcium hydroxide to make a 0.2 M solution, Arthur needs to follow the formula:
C1V1 = C2V2
Where:
C1 = initial concentration (0.5 M)
V1 = initial volume
C2 = final concentration (0.2 M)
V2 = final volume (10 mL)
Rearranging the formula, we can solve for V1:
V1 = (C2V2) / C1
Let's calculate the value of V1:
V1 = (0.2 M * 10 mL) / 0.5 M
V1 = (2) / 0.5
V1 = 4 mL
Therefore, Arthur needs to add 4 mL of the 0.5 M solution to 6 mL of water.
So, the correct answer is C. He needs to add 4 mL of the 0.5 M solution to 6 mL of water.
To dilute a solution, you need to add a solvent (usually water) to decrease the concentration of the solute. In this case, Arthur needs to dilute the 0.5 M calcium hydroxide solution to a concentration of 0.2 M.
The equation to calculate the dilution is as follows:
C1V1 = C2V2
Where:
C1 = initial concentration of the solution (0.5 M)
V1 = initial volume of the solution to be diluted (unknown, let's call it x)
C2 = desired concentration of the diluted solution (0.2 M)
V2 = final volume of the diluted solution (10 mL)
Now let's solve for x:
0.5 M * x = 0.2 M * 10 mL
0.5x = 2
x = 4 mL
Therefore, to dilute the 0.5 M solution of calcium hydroxide to 0.2 M in 10 mL, Arthur needs to add 4 mL of the 0.5 M solution to 6 mL of water.
So, the correct answer is option C. Arthur needs to add 4 mL of the 0.5 M solution to 6 mL of water.