Question

The standard enthalpy of formation of NH₄Cl(s) is -315.4 kj/mol. the equation that describes this ∆H°f is:

a. NH₄⁺ (aq) + Cl⁻(s) → NH₄Cl(s)
b. 1/2 N₂(g) + 2H₂(g) + 1/2 Cl₂(g) → NH₄Cl(s)
c. N₂(g) + Cl₂(g) + 4H₂(g) → NH₄Cl(s)
d. 1/2 N₂(g) + 1/2 Cl₂(g) + 1/2 H₂(g) → NH₄Cl(s)
e. N₂(g) + H₂(g) + Cl₂(g) → 2NH₄Cl(s)

Answer 1

b.1/2 N₂(g) + 2H₂(g) + 1/2 Cl₂(g) → NH₄Cl(s).

The standard enthalpy of formation of NH₄Cl(s) corresponds to the reaction for its formation from the elements in their most stable forms, which is represented by option 'b':

Step-by-step explanation:

The standard enthalpy of formation, ∆H°f, is defined for the formation of one mole of a compound from its elements in their most stable forms and standard state conditions.

Therefore, the correct equation for the standard enthalpy of formation of NH₄Cl(s) is the one that represents its formation from nitrogen (N₂(g)), hydrogen (H₂(g)), and chlorine (Cl₂(g)) in their elemental and standard state forms. The equation needs to balance out so that one mole of NH₄Cl(s) is formed.

Looking at the options provided, only option 'b' fits this description which is: 1/2 N₂(g) + 2H₂(g) + 1/2 Cl₂(g) → NH₄Cl(s).