Question

A solution contains a mixture of na2co3 and naoh. Using ph as indicator 25 ml of mix required 19.5 ml of 1 n hcl for the end point. With meoh, 25 ml of the solution required 25 ml of the same hcl for the end point. Calculate gms/l of each substance in the mixture.

Answer 1

Answer:

Let us assume that 'a' and 'b' are the Meq of Na2CO3 and NaOH, respectively

When phenolphthalein is used as an indicator:

(1/2) Meq of Na2CO3 + Meq of NaOH = Meq of HCl

(a/2) + b = 19.5 x 0.995

(a/2) + b = 19.4 -----(i)

Now, when MeOH is used as indicator:

Meq of Na2CO3 + Meq of NaOH = Meq of HCl

a + b = 25 x 0.995

a + b = 24.875 -----(ii)

Subtracting equation (i) from (ii), we get

(a/2) = 5.475

or a = 10.95

putting this value in equation (ii), we get

b = 24.875 - 10.95 = 13.925