Question

In the laboratory a student combines 46.4 mL of a 0.178 M potassium fluoride solution with 24.3 mL of a 0.316 M ammonium fluoride solution.

What is the final concentration of fluoride anion ?

Answer 1

Concentration of mixture = (n1*C1*V1+ n2*C2*V2) / (V1+V2)

where C1 --> Concentration of 1 component

V1-->volume of 1 component

C2 --> Concentration of other component

V2-->volume of other component

n1 --> number of particle from 1 molecule of 1st component

= 1 as 1 molecule of KF gives 1 F- ion

n2 --> number of particle from 1 molecule of 2nd component

= 1 as 1 molecule of NH4F gives 1 F- ion

use:

C = (n1*C1*V1+ n2*C2*V2) / (V1+V2)

C = (1*0.178*46.4+1*0.316*24.3)/(46.4+24.3)

C = 0.2254 M

Answer: 0.225 M