Question

How would I calculate the final concentration of each anion solution after equal amounts are combined to make 1 mL of the known solution. Anions are 0.20M of NaBr, NaCl, NaI and Na2SO4 and 2.0M Na2CO3.

Answer 1

Ans. All compounds dissociate into one anion per molecule of respective molecules.

Since, all 5 solutions are taken in equal volume to make 1.0 mL final volume, their volume must be equal to 0.2 mL each.

So, we have final volume of the solution = 1.0 mL

Initial volume = 0.2 mL each.

Now, using, M1V1 = M2V2        --- equation 1

Where, M1= molarity of initial solution 1, V1= volume of initial solution 1 (respective initial solution)

            M2= molarity of final solution 2, V2= volume of final solution 2 (respective final solution)

NaBr:    0.20 M x 0.2 mL = M2 x 1.0 mL

            So, M2 = 0.04 M. Thus, final concentration of Br^- in 1.0 mL solution = 0.04 M

NaCl: 0.20 M x 0.2 mL = M2 x 1.0 mL

            So, M2 = 0.04 M. Thus, final concentration of Cl^- in 1.0 mL solution = 0.04 M

NaI: 0.20 M x 0.2 mL = M2 x 1.0 mL

            So, M2 = 0.04 M. Thus, final concentration of I^- in 1.0 mL solution = 0.04 M

Na₂SO₄: 0.20 M x 0.2 mL = M2 x 1.0 mL

            So, M2 = 0.04 M. Thus, final concentration of SO₄^2- in 1.0 mL solution = 0.04 M

Na₂CO₃ : 2.0 M x 0.2 mL = M2 x 1.0 mL

            So, M2 = 0.4 M. Thus, final concentration of CO₃^2- in 1.0 mL solution = 0.4 M

Since, no K_sp data is provided, it’s assumed that concentration of anion is not affected by common-ion effects.