Triphenylmethanol can also be prepared by reacting ethyl benzoate with phenylmagnesium bromide, and by reacting diethylcarbonate with phenylmagnesium bromide. write stepwise rxn mechanisms for these two reactions

Both reactions proceeds  through nucleophilic acyl substitution reaction

Explanation:

Both these two reactions proceeds through nucleophilic acyl substitution reaction where phenyl magnesium bromide replaces one ethoxide ion.Then another another equivalent of phenyl magnesium bromide give nucleophilic addition reaction with resulting keto group to produce triphenylmethanolFull reaction mechanism has been shown below    

They can measure  the amount of energy gained or lost