Question

The thermodynamic information for the following reaction is as follows:

HNO3 (g) + H2 (g) → NH3 (g) + H2O (g) △H = −637 kJ

1) Balance the chemical reaction.

2) Identify this reaction as endothermic or exothermic.

3) Calculate how much heat is released when 7.20 g of H2 reacts in this situation.

Answer 1

1. HNO₃ (g) + 4H₂ (g) ⇒ NH₃ (g) + 3H₂O (g)

2. Exothermic.

3. 2293.2 kJ

Further explanation

Reaction

HNO₃ (g) + H₂ (g) ⇒ NH₃ (g) + H₂O (g) △H = −637 kJ

1. Balance

give coefficient :

HNO₃ (g) + aH₂ (g) ⇒ bNH₃ (g) + cH₂O (g)

H, left=1+2a, right=3b+2c⇒1+2a=3b+2c(eq 1)

N,left=1, right=b⇒b=1

O,left=3, right=c⇒c=3

eq 1 : 1+2a=3.1+2.3⇒1+2a=9⇒2a=8⇒a=4

Balance reaction :

HNO₃ (g) + 4H₂ (g) ⇒ NH₃ (g) + 3H₂O (g)

2. exothermic⇒release heat(negative sign)

3. heat released :

mol H₂ :

`\tt mol~H_2=(7.2)/(2)=3.6`

heat released :

`\tt -637* 3.6=-2293.2~kJ`