How much energy is required to decompose 612 g of pcl3, according to the reaction below? the molar mass of pcl3 is 137.32 g/mol and may be useful. 4 pcl3(g) ? p4(s) + 6 cl2(g) ? h°rxn = +1207 kj
a.1.85 × 103 kj
b.3.46 × 103 kj
c.5.38 × 103 kj
d.1.34 × 103 kj
e.4.76 × 103 kj?

The reaction is:

4 PCl3 (g) ---> P4(s) + 6 Cl2(g).

Now, you need to convert the mass of PCl3 into number of moles, for which you use the molar mass of PCl3 in this way:

number of moles = number of grams / molar mass =>

number of moles of PCl3 = 612 g / 137.32 g/mol = 4.4567 moles of PCl3.

Now use the proportion with the ΔH rxn given.

4 mol PCl3 / 1207 kJ = 4.4567 mol / x => x = 4.4567 mol * 1207 kJ / 4 mol = 1,344.8 kJ = 1.34 * 10^3 kJ.

1.34 * 10 ^3 kJ (option d)