Question

you are given a 2m stock solution of nacl and are asked to make up 100 ml of a 1m solution of nacl. how do you do that, using the stock solution and distilled water? select one: a. i would add 20 ml of the stock to 80 ml of water. b. i would add 50 ml of the stock to 50 ml of water. c. i would add 10 ml of the stock to 40 ml of water. d. i would add 2 ml of the stock to 98 ml of water. clear my choice

Explanation:

Step1: Use dilution formula

$C_1V_1 = C_2V_2$, where $C_1$ is initial concentration, $V_1$ is initial volume, $C_2$ is final concentration and $V_2$ is final volume.
Given $C_1 = 2M$, $C_2=1M$, $V_2 = 100\ ml$.
We need to find $V_1$.

Step2: Rearrange formula to solve for $V_1$

$V_1=\frac{C_2V_2}{C_1}=\frac{1M\times100\ ml}{2M}=50\ ml$.
Since final volume is 100 ml, volume of water to be added is $100 - 50=50\ ml$.

Answer:

B. I would add 50 ml of the stock to 50 ml of water.