Question

Which reaction shows that the enthalpy of formation of H2S is Hf = -20.6 kJ/mol?A.H2(g) + S(s)  H2S + 20.6 kJ

B.H2(g) + S(s) + 20.6 kJ  H2S
C.2H(g) + S(s) + 20.6 kJ  H2S
D.H2(g) + S(s)  H2S - 20.6 kJ​

Answer 1

H₂(g) + S(s) → H₂S + 20.6 KJ

Step-by-step explanation:

The energy changes occur during the bonds formation and bonds breaking.

There ere two types of reaction endothermic and exothermic reaction.

Endothermic reactions:

In this type of reaction energy needed to break the bond are higher than the energy released during bond formation.

For example:

C + H₂O → CO + H₂

ΔH = +131 kj/mol

it can be written as,

C + H₂O + 131 kj/mol → CO + H₂

Exothermic reaction:

In this type of reaction energy needed to break the bonds are less than the energy released during the bond formation.

For example:

Chemical equation:

C + O₂ → CO₂

ΔH = -393 Kj/mol

it can be written as,

C + O₂ → CO₂ + 393 Kj/mol

The formation of hydrogen sulfide is exothermic reaction.

H₂(g) + S(s) → H₂S ΔH = -20.6 KJ

It will be written as,

H₂(g) + S(s) → H₂S + 20.6 KJ