Question

Kim dissolves 70.13 g of solid sodium chloride (NaCl) in enough distilled water to make 400 mL of stock solution. What volumes of stock solution and distilled water (DI) are needed to make a 150 mL solution of 1.2 M NaCl?

Answer 1

This problem is providing us with the mass of solid sodium chloride and the volume of water it was dissolved in. Thus, after diluting it, the volume of the stock solution was required and found to be 60. mL according to:

Diluted solutions

In chemistry, when we are given a stock solution with specified volume and concentration, one is able to dilute it in order to use it for a specific purpose. This, by holding the number of moles constant, one can write:

$C_1V_1=C_2V_2$

Where the subscript 1 stands for the stock solution and 2 for the diluted one. Thus, one first calculate the initial concentration with the mass and volume:

$M=\frac{70.13g/(58.44 g/mol)}{0.400L}=3.00M$

Next, we solve for the volume of the stock solution, V1, as follows:

$V_1=\frac{C_2V_2}{C_1}$

Finally, we plug in the given data to obtain the result:

$V_1=\frac{1.2M*150mL}{3.00M}\\ \\V_1=60.mL$

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