Experiment 5: Back Titrations - Antacid Titration Analysis

Question 1

How does back titration work?

Answer 1

Dissolving antacid tablets in excess acid, then determine how much acid remains by titrating with NaOH.

Question 2

Using back titration, how to determine amount of acid neutralized by the antacid tablet?

Answer 2

Subtract amount of initial HCl added by amount of NaOH needed to titrate to endpoint.

Question 3

titrant definition

Answer 3

a solution of known concentration that is added (titrated) to another solution to determine the concentration of a second chemical species

Question 4

what does it mean if more titrant is needed to reach the end point in back titration

Answer 4

• If more titrant is required to reach the endpoint in a back titration compared to a regular titration, it suggests that the analyte reacted with a portion of the excess titrant that was added initially
• This indicates that the analyte is either partially or completely consumed by a reaction with the excess titrant.

Question 5

what does it mean if less titrant is needed to reach the end point in back titration

Answer 5

• less titrant is needed to reach the endpoint in a back titration, it suggests that some of the excess titrant added initially remains unreacted after the analyte has been consumed
• this typically occurs when the reaction between the analyte and the titrant is faster or more complete than anticipated

Question 6

procedural steps

Answer 6

• fill one burette with standardized HCl and the other with standardized NaOH
• add 25-30 mL of standardized HCl to the sample and allow the tablet to react with the acid for 3-5 mins
• place flasks on hot plate to drive off CO2
• add required indicator then use the back-titration method to titrate against NaOH