Briefly describe what purpose each of these chemicals serve

Briefly describe what purpose each of these chemicals serve in an experiment:

a. Anhydrous Na2SO4 in a reaction work up

b. The 6N HCL in the synthesis of triphenylmethanol.

c. The thiamine hydrochloride used in the synthesis of benzoin.

d. The nitric acid used in the preparation of benzil.

Solution

a) anhydrous Na2SO4 is used to remove water from solution as it is a drying agent

b) used for neutralizing the reaction mixture and inducing the hydrolysis

c) used as a catalyst in the reaction

d) oxidising agent