Question

Write the formation reactions for the following substances: solid aluminum chloride, AH° = -704.9 kJ/mol (5) (g) - 1 AlCIa = gaseous carbon, AH° = 717.5 kJ/mol

aqueous ammonium ion, AH° = -132.5 kJ/mol

Answer 1

Formation reactions are written for compounds forming from their constituent elements in their standard states.

Step-by-step explanation:

Writing formation reactions for compounds involves balancing a reaction where the elements in their standard states combine to form one mole of the compound. The enthalpy change for this process is called the standard enthalpy of formation (ΔHfo). Let's approach each substance systematically:

Solid Aluminum Chloride (AlCl3)

The formation reaction for solid aluminum chloride from aluminum and chlorine is:

2Al(s) + 3Cl2(g) → 2AlCl3(s) with ΔHfo = -704.9 kJ/mol

Gaseous Carbon (C(s)

Gaseous carbon does not have a standard enthalpy of formation since it is not commonly found in the gaseous state at standard conditions.

Aqueous Ammonium Ion (NH4+)

The aqueous ammonium ion is formed from the elements in their standard states, yet the equation would be more complex due to the involvement of a proton (H+) and an electron (e-) to form NH4+ in solution. The exact enthalpy can be tricky to ascertain without more context, but its ΔHfo value given is -132.5 kJ/mol.