Question

Nitrogen and Oxygen form $N_{2}O$, NO, $NO_{2}$, $N_{2}O_{4}$, $N_{2}O_{5}$. Which Law of chemical combination is followed?

Answer 1

law of const propotion :)

Answer 2

There are five laws which govern the chemical combinations namely

i) Law of conservation of mass  

ii) Law of definite proportions

iii) Law of multiple proportions

iv) Law of reciprocal proportions  

v) Gay Lussac's Law of Gaseous Volumes

Among these four are pertaining to mass whereas the last one is about volume of gases.

In the given example two elements nitrogen and oxygen combine to give

i) ${ N }_{ 2 }O$  

ii) NO  

iii) ${ NO }_{ 2 }$

iv) ${ N }_{ 2 }{ O }_{ 4 }$  

v) ${ N }_{ 2 }{ O }_{ 5 }$  are five different compounds. This follows the Law of Multiple proportions.

Law of multiple proportions states that when two elements combine with each other to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.

Let us keep the weight of nitrogen a fixed one. Since, in three compounds two nitrogen atoms are present, let us accordingly change the formula of others suitably NO as ${ N }_{ 2 }{ O }_{ 2 }$ and ${ NO }_{ 2 }$ as ${ N }_{ 2 }{ O }_{ 4 }$. Thus, we have the formulae as  

i) ${ N }_{ 2 }O$  

ii) ${ N }_{ 2 }{ O }_{ 2 }$

iii) ${ N }_{ 2 }{ O }_{ 4 }$  

iv) ${ N }_{ 2 }{ O }_{ 4 }$  

v) ${ N }_{ 2 }{ O }_{ 5 }$

Now, the fixed weight of nitrogen in all the compounds is 28 g and the weight of oxygen in corresponding compounds are 16g , 32g, 64 g, 64 g and 80 g respectively. The ratio works out to be 1:2:4:4:5 which is a whole number ratio.