Due to small size and high electronegativity and presence of lone pair(s) of electrons, elements N, O, F when bonded to hydrogen atom, forms intermolecular hydrogen bonds which are stronger than other intermolecular forces. This results in exceptionally high melting and boiling points of the compounds.

Deuterium is another name for heavy hydrogen. It differs from hydrogen in its nucleus, as it contains a neutron as well as a proton, making the atom extra heavier.

Ortho and para hydrogen show different spins in a hydrogen molecule, so they are not isotopes of hydrogen.

The sulphates become less soluble om going down the group.

Mg > Ca > Sr > Ba

This is due to the decrease in hydration energy from Be²⁺ to Ba²⁺ as the size of the cation increase down the group. The significantly High solubility of MgSO₄ is due to the high enthalpy of hydration of the smaller Mg²⁺ ions. However, the magnitude of lattice energy remains almost constant as the size of the sulphate ion is so big that small increase in the size of the cation from Be to Ba does not make any difference.

Li⁺ is smallest in size and therefore has maximum charge density.

Among all the alkali metal ions, it is most heavily hydrated because the effective size of Li⁺ in aqueous solution is the largest. Therefore, Li⁺ will move the slowest under electric field.

sodium carbonate is prepared by solvay process which exploits the low solubility of sodium hydrogen carbonate whereby it gets precipitated in the reaction of sodium chloride with ammonium hydrogen carbonate.

The ammonium hydrogen carbonate is prepared by passing CO₂ to a concentrated solution of sodium chloride saturated with ammonia, where ammonium carbonate followed ammonium hydrogen carbonate are formed.

Sodium hydrogen carbonate crystals separate. These are heated to give sodium carbonate.

calcium oxide is also called as quick lime. It is prepared on a commercial scale by heating limestone in a rotator kiln at 1070- 1270K.

above 393 K, on heating gypsum no water of crystalline is left and anhydrous calcium sulphate, CaSO₄ is formed. This is known as ‘dead blunt plaster’.

cement is obtained by combining CaO with clay, which contains silica, SiO₂ along with oxides of aluminium, iron and magnesium. The average composition of Portland cement is- 

CaO = 50 to 60%

SiO₂ = 20- 25%

Al₂O₃ = 5-10%

MgO = 2-3%

Fe₂O₃ = 1-2%

SO₃ = 1-2%