Question

A student has 100. mL of 0.20 M HCl solution. She takes 5.0 mL of this solution, and adds it to 10.0 mL of water. She then takes 3.0 mL of this new solution for an experiment. What is the concentration of this solution?

Answer 1

from 100 ml 0.20 M HCl solution student take 5.0 ml

thus initial concentration of 5 ml solution = 0.20 M

and add 10 ml water to this 5 ml solution thus final volume = 5 + 10 = 15 ml

Use the formula C₁V₁ = C₂V₂

Where C₁ = initial concentration = 0.20 M

V₁ = initial volume = 5 ml

C₂ = final concentration = ?

V₂ = final volume = 15 ml

Substitute the value in formula

C₁V₁ = C₂V₂

C₂ = C₁V₁/V₂

= 0.20 5/15

C₂ = 0.0667 M

15 ml solution have concentration = 0.0667 M

from this she taken 3 ml therefore concentration of this solution = 0.0667 M