Question

You have 750. mL of a 1.2 M sodium chloride solution, but you need to concentrate it to 3.5 M. How much water do you need to evaporate from the solution to reach this concentration

Answer 1

493 mL has to evaporate

Step-by-step explanation:

Step 1: Data given

Initial volume of the sodium chloride (NaCl) solution = 750 mL = 0.750 L

Molarity of the sodium chloride (NaCl) solution = 1.2 M

The concentration needed = 3.5 M

Step 2: Calculate the volume needed

To have a higher concentration we should lower the volume

C1*V1 = C2*V2

⇒C1 = the original concentration = 1.2 M

⇒V1 = the initial volume = 0.750 L

⇒C2 = the new concentration = 3.5 M

⇒V2 = the new volume needed = TO BE DETERMINED

1.2 M * 0.750 L = 3.5 M * V2

V2 = 0.257 L

To have a concentration of 3.5 M we need 0.257 L or 257 mL

Step 3: Calculate the volume of water to evaporate

750 mL - 257 = 493

493 mL has to evaporate