Question

Unknown acid 2 6. Complete the following table. Trial 1 Trial 2 Trial 3 Mass of unknown (8) 0.175 0.120 0.122 Initial buret reading (mL) 0.00 22.37 0.00 Final buret reading (mL) 22.37 44.85 22.83 Volume of NaOH added (mL) 22.37 22.48 22.83 We will assume that the data collected for the first trial is not accurate. 7. What is the average mass of unknown acid for Trials 2 and 3? (Must show calculations) 8. What is the average volume of NaOH added in L for Trials 2 and 3? (Must show calculations) 9. Calculate the molar mass of the unknown diprotic acid. (Must show calculations) L NaOH mol NaOH L NaOH + mol acid mol NaOH. = mol acid g acid = molar mass acid mol acid 10. What is the identity or name of the unknown acid 2? 11. Why do we NOT need to measure the pH and create a titration curve (mL of NaOH added versus pH) to determine the molar mass of an unknown diprotic acid? Use your results from experiment 09 as a reference.

Answer 1

Titration: Titration is a technique used in analytical chemistry for qualitative and quantitative estimation of unknown substance by using a known chemical. Titration is based on the various reactions such as neutralization reaction, redox reaction among others. It has wide application in different of analytical researches and practices.

Given table is shown below.

	Trial 1	Trial 2	Trial 3
Mass of unknown acid (g)	0.115	0.120	0.122
Initial burette reading (mL)	0.00	22.37	0.00
Final burette reading (mL)	22.37	44.85	22.83
Volume of NaOH added (mL)	22.37	22.84	22.83

Ans 7. Given mass of unknown acid for trial 2 is 0.120

Given mass of unknown acid for trial 3 is 0.122

Average of mass can be calculated by using the given formula.

Ans 8. The volume of NaOH added in trial 2 is 22.48 mL or 0.0224 L

The volume of NaOH added in trial 3 is 22.83 mL or 0.0228 L

Average of volume can be calculated by using the given formula.

9.

Ans 9. Molar mass of unknown diprotic acid is calculated by the given formula.

Ans 10. The molar mass of diprotic acid is calculated to be 107 g/mol.

Refering to the data given, the value is closest to the molar mass of malonic acid, which is 104 g/mol.

Therefore, the unknown diprotic acid is estimated to be malonic acid.