[G2]

Hello. I am determining the molecular weight of an unknown acid. I titrated with NaOH I and my partner standardized a week before. The concentration is 0.2651 M. The amount used to reach the equivalence point was 8.1 ml and the weight of unknown acid was 0.2467 g. The molecular weight I received was 114.8 g/mol. I just have some questions: What is the significance of the equivalence point. I know that it is when the concentration of Hydronium ion is equal to Hydroxide ion but why is it significant in our calculations. Also, is the Ka1 of a diprotic acid equal to the pH of the initial solution of deionized water and unknown acid or is it equal to the anti-log of the equivalence point. I am in Analytical Chemistry but I feel like I am still in General Chemistry because my lab instructor takes a toll on my knowledge and I begin to question myself. Thank you for your help.

[Borek]

What is the significance of the equivalence point. I know that it is when the concentration of Hydronium ion is equal to Hydroxide ion but why is it significant in our calculations.

No, that's not a definition of equivalence point.

http://www.titrations.info/titration-basic-terms#equivalence-point

Also, is the Ka1 of a diprotic acid equal to the pH of the initial solution of deionized water and unknown acid or is it equal to the anti-log of the equivalence point.

Neither.

I am in Analytical Chemistry but I feel like I am still in General Chemistry because my lab instructor takes a toll on my knowledge and I begin to question myself.

It is more or less like stating "I feel like I am in elementary school, because my lab instructor takes a toll on my ability to read". You have learned things in General Chemistry to use them later, not to forgot them the day the class ended.

[G2]

Please explain if you can rather than give two letter answers.

[Borek]

Please explain if you can rather than give two letter answers.

I posted link to the definition, have you read it?