Question

Show how to prepare 150 grams of solution which is 7.5% NaCl by weight
concentration.
a. What weight of Solute is needed (show computations)?
b. What weight of Water is needed (show computations)?

Answer 1

The mass of NaCl needed for the solution is:

$150g\times0.075=11.3g$

Therefore, the mass of water is $150g-11.3g=138.7g$.

Assuming that the density of water is equal to $0.9982g/mL$ at 20^oC, the volume of water needed is $V=\frac{138.7g}{0.99982g/mL}=139mL$

So, in order to prepare this solution, 11.3 g of NaCl should be weighted and added to 139 mL of pure water.