Chemistry

Carbon dioxide can be obtained as a solid in the form of dry ice by allowing the liquified CO₂ to expand rapidly.
Unlike ordinary ice it does not melt and hence does not wet the surface on which it is kept. Thus, it is called dry ice.

The catenation depends on the strength of the element-element bond. As we move down the group 14, the element-element bond energies decrease rapidly, viz. C–C (355 kJ mol–1), Si–Si (222 kJ mol–1), Ge–Ge (167 kJ mol–1) and Sn–Sn (155 kJ mol–1), so the tendency for catenation decreases in the order C > Si > Ge > Sn.

Carbon atoms have the tendency to linkwith one another through covalent bonds to form chains and rings. This property is calledcatenation. This is because C—C bonds are very strong.

Boron shows anomalous behaviour due to small atomic size, high electronegativity, high ionization energy and absence of d-orbital of B

  (b) SiO₄^4- is the basic unit of all silicates.

(a) Producer gas is a mixture of CO and N₂ in the ratio of 2 :1

(d) CO₂ is regarded as anhydride of carbonic acid.

H₂CO₃ ————> H₂O + CO₂

(d) is an incorrect statement because non-metal oxides are acidic or neutral whereas metal oxides are basic in nature.

(c) Boron halides are Lewis acids and can accept a pair of electrons from amines to form addition product.