What is the molecular formula of formic acid (methanoic acid)?

Give a name to the reaction which takes place between ethanoic acid and ethanol in the presence of concentrated sulphuric acid. Write the chemical reaction and the name of the product obtained.

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.

Carbon does not form ionic compounds. Why?

Explain the following reactions with chemical equations:
$(i)$ Oxidation
$(ii)$ Hydrogenation
$(iii)$ Substitution

Carbon forms four covalent bonds by sharing its four valence electrons with four univalent atoms,e.g.,hydrogen. After the formation of four bonds,carbon attains the electronic configuration of: