What conversion occurs in the formation of milk into curd?

$(a)$ What are hydrocarbons?
$(b)$ Write the structural difference between saturated and unsaturated hydrocarbons.

$A$ molecule of ammonia has the formula $NH_{3}$. Predict the total number of bonds present around the nitrogen atom.

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

On dropping a small piece of sodium in a test tube containing carbon compound $X$ with molecular formula $C_{2}H_{6}O$,a brisk effervescence is observed and a gas $Y$ is produced. On bringing a burning splinter at the mouth of the test tube,the gas evolved burns with a pop sound. Identify $X$ and $Y$. Also,write the chemical equation for the reaction. Write the name and structure of the product formed when you heat $X$ with excess concentrated sulphuric acid.

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