Question

Consider the following hypothetical reaction:

A + 3B ⇄ 2C + D

A titration was performed in which a standardized solution of A was used as the titrant, and an unknown amount of B was the analyte. The concentration of A in the standardized solution was 0.2005 M (± 0.4%). The initial buret reading was 2.45 mL, and the final buret reading (at the endpoint) was 42.06 mL

a) How many moles of B were present in the unknown sample?

b) If the tolerance of the buret is ±0.06 mL, what is the absolute uncertainty associated with your answer to part A?

Answer 1

a) since, The initial buret reading was 2.45 mL, and the final buret reading (at the endpoint) was 42.06 mL
hence the total volume of A needed is = 39.61 ML.

The concentration of A reactant in the standardized solution was 0.2005 M (± 0.4%).

this means 1000ML soltuin contains 0.2005 moles of A reactant

so, in 39.61 ML solution of A caontains = 0.2005 X 39.61/1000 = 0.0079 moles of A reactant.

as from the reaction A + 3B ----------- 2C + D. we can understan that 1 mole of A react with 3 mole of B.

hence for the tritation at end point the moles of B were present in the unknown samlpe is

= 3 x 0.0079 = 0.0238 mole