Question

Complete the following statements by selecting the correct option :

(a) The formula of a compound represents

(i) an atom (ii) a particle

(iii) a molecule (iv) a combination.

(b) The correct formula of aluminium oxide is

(i) AIO${}_3$ (ii) AIO${}_2$ (iii) AI${}_2$O${}_3$

(c) The valency of nitrogen in nitrogen dioxide (NO${}_2$) is

(i) one (ii) two

(v) three (iv) four.

Answer 1

(a) The formula of a compound represents
(i) atom
The chemical formula of a particular compound represents the number of different types of atoms in its molecule. For instance, the compound $C{O}_2$ (carbon dioxide) has one carbon atom and two oxygen atoms. It does not represent the size or shape of the molecule or the number of molecules in the compound.

(b) The correct formula of aluminium oxide is:
(iii) Aluminium oxide (British English) is a chemical compound of aluminium and oxygen with the chemical formula $A{l}_2{O}_3$. It is the most commonly occurring of several aluminium oxides and specifically identified as aluminium(III) oxide.

(c) The valency of nitrogen in nitrogen dioxide $N{O}_2$ is
(iv) Valency of N in $N{O}_2$ :
Let X be the valency of N
X + 2(-2)=0
X = 4