What is the molecular formula of methanal?

How would you name the following compounds?
$(i)$ $CH_{3}-CH_{2}-CH=CH_{2}$
$(ii)$ $CH_{3}-CH_{2}-CH_{2}-C(CH_{3})_{2}-CH_{3}$
$(iii)$ $CH_{3}-CH_{2}-CHO$
$(iv)$ $CH_{3}-CH(OH)-CH_{3}$

What is the boiling point of methanal (in $,K$)?

$A$ compound $C$ (molecular formula $C_2H_4O_2$) reacts with $Na$ metal to form a compound $R$ and evolves a gas which burns with a pop sound. Compound $C$ on treatment with an alcohol $A$ in the presence of an acid forms a sweet-smelling compound $S$ (molecular formula $C_3H_6O_2$). On addition of $NaOH$ to $C$,it also gives $R$ and water. $S$ on treatment with $NaOH$ solution gives back $R$ and $A$. Identify $C$,$R$,$A$,$S$ and write down the reactions involved.

An organic compound $'A'$ has a molecular formula $C_{2}H_{6}O$. $'A'$ on oxidation gives compound $'B'$,which produces effervescence with baking soda.
$(i)$ Identify $'A'$ and $'B'$.
$(ii)$ Write the chemical reaction of $'B'$ with baking soda.

Write the molecular formula of benzene and state the number of double bonds in its structure.