Draw the structure of the simplest ketone.

An organic compound $A$ of molecular formula $C_{2}H_{4}$ on reduction gives another compound $B$ of molecular formula $C_{2}H_{6}$. $B$ on reaction with chlorine in the presence of sunlight gives $C$ of molecular formula $C_{2}H_{5}Cl$.
$(a)$ Name the compounds $A, B$ and $C$.
$(b)$ Write the chemical equation for the conversion of $A$ to $B$ and name the type of reaction.

The correct structural formula of butanoic acid is

Look at the figure and answer the following questions:
$(a)$ If ethanol is used instead of ethanoic acid,would you expect the same change?
$(b)$ How can a solution of lime water be prepared in the laboratory?

$A$ gas is evolved when ethanol reacts with sodium. Name the gas evolved and also write the balanced chemical equation of the reaction involved.

In the presence of which enzyme does the fermentation of glucose or fructose occur to produce ethanol and carbon dioxide?