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 the concentration of stock solution, $V_1$ is the volume of stock solution, $C_2$ is the final - desired concentration, and $V_2$ is the final volume.
Given $C_1 = 2M$, $C_2 = 1M$, $V_2=100\ ml$.
We need to find $V_1$.
From $C_1V_1 = C_2V_2$, we can express $V_1=\frac{C_2V_2}{C_1}$.

Step2: Substitute values

$V_1=\frac{1M\times100\ ml}{2M}=50\ ml$.
The volume of the stock solution needed is $50\ ml$.
The volume of water needed is $V_{water}=V_2 - V_1=100\ ml - 50\ ml = 50\ ml$.

Answer:

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