Question

When Fe(s) reacts with Cl2(g) to form FeCl3(s) , 400 kJ of energy are evolved for each mole of Fe(s) that reacts. Write a balanced thermochemical equation for the reaction with an energy term in kJ as part of the equation.

Answer 1

Explanation:

A balanced equation is defined as the equation which contains the same number of atoms on both reactant and product side.

For example, when solid state of iron chemically reacts with chlorine gas then it results in the formation of a solid ferric chloride.

The chemical equation for this reaction is as follows.

     $Fe(s) + Cl_{2} \rightarrow FeCl_{3}$

Number of atoms on reactant side are as follows.

• Fe = 1

• Cl = 2

Number of atoms on product side are as follows.

• Fe = 1

• Cl = 3

Hence, to balance this equation we will multiply Fe by 2 and $Cl_{2}$ by 2 on the reactant side. Also, we multiply $FeCl_{3}$ by 2 on product side.

Therefore, the net balanced equation is as follows.    

     $2Fe(s) + 3Cl_2(g) \rightarrow 2FeCl_3(s) : \Delta H = - 2 × 400 kJ/mol \text{of Fe(s)}$

             $\Delta H = -400 \times 2$ = -800 kJ