Answer :
You start with 285mL of 0.35M solution of NaCl. Sufficient amount of water is added so that the volume increases to 550mL. What will be concentration of the new solution.
Initial volume = V₁ = 285 mL
Initial concentration = M₁ = 0.35 M
Final volume = V₂ = 550 mL
Final concentation = M₂ = ?
We are only adding water to our solution, so we are diluting the solution. The number of moles of NaCl will remain constant. Since the amount of the solute is constant, in dilution exercises we can use this formula:
V₁ * M₁ = V₂ * M₂
If we solve it for the final concentration we get:
M₂ = V₁ * M₁ / V₂
If we replace by the given values we obtain:
M₂ = 285 mL * 0.35 M / 550 mL
M₂= 0.18 M
