Answer to Question #147515 in General Chemistry for Gusty

Question

2. A 22.0 mL volume of 0.095 M NaOH is required to reach the phenolphthalein endpoint in

the titration of a 3.05 g sample of vinegar.

a. Calculate the number of moles of acetic acid in the vinegar sample.

b. Calculate the mass of acetic acid in the vinegar sample.

c. Calculate the percent by mass of acetic acid in the vinegar sample. Assume the density

of the vinegar is 1.0 g/mL.

3. In part B if the endpoint of the titration is overshot! Does this technique error result in an increase, a decrease, or have no effect on the reported percent acetic acid in the vinegar?

Explain.

Answer 1

2.А

CH₃COOH + NaOH --> CH₃COONa + H₂O

a) n(CH₃COOH)= V(NaOH)*M(NaOH)=0.022*0.095=0.0021 mole;

b)m(CH₃COOH)= n(CH₃COOH)*Mr(CH₃COOH)=0.0021*60=0.126 g;

c) % mass= 0.126/3.05 *100%= 4.13 %

3.The the percent acetic acid in the vinegar is directly proportional to the amount of NaOH added. It means that this technique error result in an increase on the reported percent acetic acid in the vinegar