Question

4. How would the calculated equivalent mass of the unknown acid in this experiment be affected if:

(a) The buret was contaminated with acid solution?

(b) Not all of the unknown weighted acid was transferred to the titration beaker?

(c) The volume of distilled water in which the unknown acid was dissolved was not accurately known?

Answer 1

a) If the buret is contaminated with acid then the concentration of acid used during the titration will change (more precisely the overall concentration will be increased) and as we know that the equivalent mass of acid and its concentration are related as:

$w=\frac{MEV}{1000}$

This suggests that the equivalent mass and concentration of acid are directly proportional to each other, therefore if buret is contaminated with acid then the calculated equivalent mass of the unknown acid will be more.

b) If all the unknown weighed acid (w) is not transferred to the titration beaker then the solution so formed will be of less concentration (M) as compared to the one when all weighed acid is transferred (because both are directly proportional, check above equation) and thus the equivalent mass will also decrease.

c) If the volume (V) of distilled water added is not accurately known than the concentration of acid cannot be precisely determined and so its equivalent mass (E) will increase if the added volume is more and decrease if the added volume is less.