Q10.78CP - Chemistry: Molecular Nature Of Matter And Change

Question

An oxide of nitrogen is $\mathbf{\text{25.9\%}}$  N by mass, has a molar mass of 108 g/mol, and contains no nitrogen-nitrogen or oxygen- oxygen bonds. Draw its Lewis structure, and name it.

 

Step-by-Step Solution

Answer

Its Lewis structure is,

The name of the compound is dinitrogen pentoxide.

Step 1: Mass of components.

Consider that the total mass of the compound is 100g.

Given that the mass of nitrogen is 25.9g.

 

So, the mass of oxygen will be  $\text{=100 - 25.4 = }\text{74.1g}$ .

 

Moles of nitrogen  $\text{= }\frac{\text{mass of\hspace{0.17em}nitogen}}{\text{moelcular\hspace{0.17em}mass\hspace{0.17em}of\hspace{0.17em}nitogen}}$ 

Moles of oxygen  $\text{=}\frac{\text{mass\hspace{0.17em}of\hspace{0.17em}oxygen}}{\text{moelcular\hspace{0.17em}mass\hspace{0.17em}of\hspace{0.17em}oxygen}}$

Atom	Mass present in compound	Moles present in compound	Ratio
Nitrogen	25.9	$\frac{\text{25.9}}{\text{14}}\text{=1.85}$	$\frac{\text{1.85}}{\text{1.85}}\text{=1}$
Oxygen	74.1	$\frac{\text{74.1}}{\text{16}}\text{=4.63}$	$\frac{\text{4.63}}{\text{1.85}}\text{=2.5}$

Step 2: Formula of compound

The ratio of nitrogen and oxygen is the empirical formula of the compound, i.e.,  ${\mathbf{N}}_1{\mathbf{O}}_{\mathbf{2}.\mathbf{5}}$.

Now, the empirical mass of nitrogen oxide .

$\begin{array}{c}\text{Empirical mass = molecular\hspace{0.17em}mass\hspace{0.17em}of\hspace{0.17em}nitrogen\hspace{0.17em}+\hspace{0.17em}2.5×\hspace{0.17em}molecular\hspace{0.17em}mass\hspace{0.17em}of\hspace{0.17em}oxygen}\\ \text{ = 14g/mol\hspace{0.17em}+\hspace{0.17em}2×16g/mol}\\ \text{ = 54g/mol}\end{array}$

$\begin{array}{c}\text{Empirical formula units = }\frac{\text{molecular\hspace{0.17em}mass}}{\text{empirical\hspace{0.17em}mass}}\\ \text{ =}\frac{\text{108}}{\text{54}}\\ \text{ =\hspace{0.17em}2g/mol}\end{array}$

Therefore, the molecular formula of compound is  ${\text{N}}_{\text{2}}{\text{O}}_{\text{5}}$. 

Step 3: The Lewis structure.

The structure in which a line shows the bonding between the atoms and a dot indicates lone pair of electrons is known as the Lewis dot structure.