Question

question 1
given a stock solution of 2% dextrose, how would you prepare 10 ml of 0.5% dextrose solution?
a. volume of stock= ______ml
b. volume of water= ______ml
a. 8 ml of stock ... b. 2 ml of water
a. 2 ml of stock ... b. 8 ml of water
a. 2.5 ml of stock ... b. 7.5 ml of water

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 concentration of final solution and $V_2$ is the volume of final solution. Given $C_1 = 2\%$, $C_2=0.5\%$, $V_2 = 10$ ml. We need to find $V_1$.
$V_1=\frac{C_2V_2}{C_1}=\frac{0.5\%\times10}{2\%}$

Step2: Calculate volume of stock solution

$V_1=\frac{0.5\times10}{2}= 2.5$ ml

Step3: Calculate volume of water

The volume of water $V_w=V_2 - V_1$. Since $V_2 = 10$ ml and $V_1 = 2.5$ ml, $V_w=10 - 2.5=7.5$ ml

Answer:

A. 2.5 ml of stock ... B. 7.5 ml of water