Question

Sally needs to make a 35% solution of sodium chloride for several different lab groups. To make her time more efficient, she decides to make a stock of 5 L that will last through the whole week. After doing her math, Sally weighs out 175 g of sodium chloride, places it in a large carboy, and adds water to make 5 L of solution. Has Sally made the correct concentration of solution? Why or why not?

a) No, using 175 g of sodium chloride in 5 L of solution will give a .35% solution.
b) Yes, using 175 g of sodium chloride in 5 L of solution will give a 35% solution.
c) No, using 175 g of sodium chloride in 5 L of solution will give a 3.5% solution.

Answer 1

Answer: c) No, using 175 g of sodium chloride in 5 L of solution will give a 3.5% solution.

Explanation:

Percent of solution = 35 %

Mass of solute = 175 g

Volume of solution = 5L = 5000 ml     (1L=1000ml)

Mass by volume percent (m/v)% : It is defined as the mass of solute present in 100 ml of solution.

Formula used :

$(m/v)\%=\frac{\text{Mass of solute}}{\text{Volume of solution}}\times 100$

Now put all the given values in this formula:

$(m/v)\%=\frac{175g}{5000ml}\times 100=3.5\%$

Thus the mass by volume percent is 3.5 % and not 35%.