Question

1. For each of the following circumstances, indicate wheter the calculated molarity of NaoH would be lower, higher, or unaffected. Explain your answer in each case.

a. The inside of the pipet used to transfer the standard HCl solution was wet with water.
b. You added 40 mL of water to the titration flask rather than 25 mL.
c. The buret, wet with water, was not rinsed with NaOH solution before filling the buret with NaOH with solution.
d. Five (5) drops of phenolphthalein were added to the solution to be titrated rather than three (3) drops.

Answer 1

1. For each of the following circumstances, indicate wheter the calculated molarity of NaOH would be lower, higher, or unaffected. Explain your answer in each case.

a. The inside of the pipet used to transfer the standard HCl solution was wet with water.

Ans:

Less number of moles of HCl are used in titration .

Hence, the calculated molarity of NaOH would be higher.

b. You added 40 mL of water to the titration flask rather than 25 mL.

Ans: Unaffected. Volume of water in the titration flask is not counted during calculations.

c. The buret, wet with water, was not rinsed with NaOH solution before filling the buret with NaOH with solution.

Ans: Less volume of NaOH are used in titration .

Hence, the calculated molarity of NaOH would be lower.

d. Five (5) drops of phenolphthalein were added to the solution to be titrated rather than three (3) drops.

Ans: Unaffected. A little excess of phenolphthalein will not significantly affect the calculated molarity of NaOH.