Question

Match the following compounds with their molecular mass.

(i) ${\text{SO}}_2$ (ii) ${\text{CO}}_2$ (iii) ${\text{NO}}_2$ (iv) ${\text{H}}_2\text{O}$

(a) 44 u (b) 64 u (c) 18 u (d) 46 u

• A. (i)- (a), (ii)- (d), (iii)- (b), (iv)- (c)
• B. (i)- (b), (ii)- (d), (iii)- (a), (iv)- (c)
• C. (i)- (b), (ii)- (a), (iii)- (d), (iv)- (c)
• D. (i)- (c), (ii)- (d), (iii)- (b), (iv)- (a)

Answer 1

The correct option is C

(i)- (b), (ii)- (a), (iii)- (d), (iv)- (c)

The mass of one molecule of an element or compound is known as molecular mass. It is represented by 'u'.

Molecular mass of ${\text{SO}}_2$= Atomic mass of sulphur + 2 $\times$ Atomic mass of oxygen
Molecular mass of ${\text{SO}}_2$= $32+2\times 16$ = $64u$

Molecular mass of ${\text{CO}}_2$= Atomic mass of carbon + 2 $\times$ Atomic mass of oxygen
Molecular mass of ${\text{CO}}_2$ = $12+2\times 16$ = $44u$

Molecular mass of ${\text{NO}}_2$ = Atomic mass of nitrogen + 2 $\times$ Atomic mass of oxygen
Molecular mass of ${\text{NO}}_2$= $14+2\times 16$ = $46u$

Molecular mass of ${\text{H}}_2\text{O}$ = 2 $\times$ Atomic mass of hydrogen + Atomic mass of oxygen
Molecular mass of ${\text{H}}_2\text{O}$= $2\times 1+16$= $18u$

Therefore, the correct match is: (i)- (b), (ii)- (a), (iii)- (d), (iv)- (c)