The following observations can be deduced from the given reaction:
Product react with at to form -methyl--butene and we know that when the vapours of tertiary alcohol are passed over heated copper at , the product formed is an alkene.
So product is a tertiary alcohol.
Now it is also known that when ketones react with Grignard reagent in presence of acid , tertiary alcohol is formed.
Therefore, product A is - methyl ethanone.
Mass percentage of carbon in compound A is where, is the weight of total carbon present in the compound i.e and is weight of compound i.e .
Mass percentage of carbon in compound is
Therefore, the mass percentage of carbon in compound is .