Unsaturated hydrocarbons produce a yellow flame with a large amount of black smoke when burnt in oxygen. Give the reason.

In which of the following compounds,$-OH$ is the functional group?

Which polymer is formed by reacting a compound containing two carboxylic acid groups and a compound containing two hydroxyl groups?

Why are detergents preferred over soaps for washing clothes in hard water? Explain.

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 structural formula of ethyne is: