Question

Nitrogen and hydrogen gases react to form ammonia gas as follows :

N2(g) + 3H2(g)  2NH3(g)

(a) At certain temperature and pressure 1.2 L of N2 reacts with 3.6 L of H2

 then, what will be the volume

of  NH3 produced.

(b) At certain temperature if N2

(g) and H2(g) are taken at 2atm and 8 atm respectively then what would

be the final pressure after the reaction .

(c) At certain temperature if N2(g) and H2(g) are taken at 2atm and 8 atm respectively and 20 %

reaction takes place then what would be the final pressure after the reaction .​

Answer 1

a)

Temperature and pressure are constant, so volume is directly proportional to mole.

Hence we can use volume as mole here.

N₂ + 3H₂ → 2NH₃

1 mole of Nitrogen gas reacts with 3 mole of hydrogen gas to form 2 mole of ammonia gas.

→ 1 Volume of Nitrogen gas reacts with 3 Volume of hydrogen gas to form 2 volume of ammonia gas.

1 litre of Nitrogen gas reacts with 3 litres of hydrogen gas

→ 1.2 litres of nitrogen gas would react with 3.6 liters of hydrogen gas

Hence, both reactants will be consumed.

1 litre of nitrogen forms 2 litre of ammonia gas

so 1.2 litres of nitrogen gas forms 2.4 litres of ammonia gas.

Hence 2.4 litres of NH₃ is formed.

$\rule{200}2$

b)

Temperature is constant, hence pressure is directly proportional to mole

N₂ + 3H₂ → 2NH₃

Given, 2 atm pressure of Nitrogen and 8 ATM pressure of hydrogen.

1 atm pressure of nitrogen requires 3 atm pressure of hydrogen.

2 atm pressure of nitrogen would require 6 arm of hydrogen.

Hence, nitrogen is limiting reagent, it'll be consumed completely but hydrogen will be left.

Hydrogen left = 8 - 6 = 2 atm

1 atm nitrogen forms 2 atm ammonia

2 atm nitrogen forms 4 atm ammonia

Hence, total pressure = 4 atm (of ammonia) + 2 atm (of hydrogen) = 6 atm pressure.

$\rule{200}2$

c) 20% reaction takes place, this means nitrogen will be left too along with hydrogen.

20% of 2 atm nitrogen will be consumed

→ 2/5 atm nitrogen consumed

Nitrogen left = 2 - (2/5) = 8/5 atm

1 atm nitrogen consumes 3 atm hydrogen

so 2/5 atm nitrogen consumes 6/5 atm hydrogen

Hydrogen left = 8 - (6/5) = 34/5 atm

1 atm nitrogen forms 2 atm ammonia

So Ammonia formed = 2/5 × 2 = 4/5 atm

Final pressure = 8/5 + 34/5 + 4/5 = 46/5 = 9.2 atm