Question

The reaction between sodium metal and chlorine gas produces 822 kJ of heat energy for every chlorine molecule consumed [2 Na(s) + Cl2(g) → 2 NaCl(s)]. How much heat is released (in kJ) if 2.972 g of Na are consumed in the reaction?

Answer 1

Answer: 53.4 kJ

Explanation:

Exothermic reactions are defined as the reactions in which energy of the product is lesser than the energy of the reactants. The total energy is released in the form of heat and $\Delta H$ for the reaction comes out to be negative.

To calculate the moles of sodium , we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text {Molar mass}}=\frac{2.972}{23}=0.13moles$

$2Na(s)+Cl_2(g)\rightarrow 2NaCl(s)$   $\Delta H=-822kJ$

According to stoichiometry, it can be seen that :

2 moles of sodium will liberate = 822 kJ

Thus 0.13 moles of sodium will liberate = $\frac{822}{2}\times 0.13=53.4 kJ$

Thus 53.4 kJ of heat is released if 2.972 g of Na are consumed in the reaction.