Question

1)How is the analytical concentration of acetic acid in 25ml pipet of raw vineger related to tis concentration after its dilution to 250ml? how is this latter concentration of acetic acid in each 25ml aliquot taken for titration?

2)Poor pipetting of raw vinegar produces a biased result (true value outside the 95% condfidence limits); it behaves as a systematic error in this procedure. Poor pippetting of a diluted vinegar produces a wide confidence interval; it behaves as a random error. what makes the same poor technique have different results?

3)you forget to weight the dry specific gravity bottle before you put in a liquid, and dont get the inside theoroughly dry before you weight it, thinking that is dr. a) will the calculation of the mass of vinager contained in the bottle to be too high or low? b) will the calculation o fthe volume of the bottle to be too high or low?

4)one advantage of the use of weight fraction as the concentration units for the legal specification of vinager is that the weight fraction of vinager does not change with temperature. the molarity of vinager does change with temperature . how is that possible? think about units.

Answer 1

1)

Volume of acetic acid in pipet (V1) =25 mL

Volume of acetic acid after dilution (V2) = 250 mL

M1 V1 = M2 V2

M1/M2 = 250 mL /25 mL

=10

Conc of acetic acid in pipet = 10 times the Conc of acetic acid after dillution ..(1)

aliquot-dillution;

Volume of acetic acid in each aliquot = 25 mL

M2V2 = M3 V3

250 mL x M2 = 25 mL x M3

M2 / M3 = 1/10

Conc of aliquot is 10 times of conc of dillusion .. (2)

From (1) and (2) conc of aliquot = conc of inital acetic acid in pipet (M1=M3)