The standard enthalpy of formation, δh°f, of hi(g) is +26 kj mol-1. which of the following is the approximate mass of hi(g) that must decompose into h2(g) and i2(s) to release 500. kj of energy?

The mass of HI that must decompose to release the given amount of energy is 2459.72 g.

Explanation:

We are given:

So, for decomposition of hydrogen iodide, the enthalpy will be -26 kJ/mol

The chemical equation for the decomposition of HI into hydrogen and iodine follows:

By Stoichiometry of the reaction:

26 kJ of energy is released when 1 mole of hydrogen iodide is decomposed.

So, 500 kJ of energy will be released when = of hydrogen iodide will be decomposed.

To calculate the mass of hydrogen iodide, we use the equation:

Moles of HI = 19.23 mol

Molar mass of HI = 127.911 g/mol

Putting values in above equation, we get:

Hence, the mass of HI that must decompose to release the given amount of energy is 2459.72 g.