Question

Nitrogen dioxide, NO2(g) (30Hf = 33.84 kJ/mol), is decomposed according to the following reaction: What is the enthalpy change when 2.50 mol of nitrogen dioxide decomposes?

Answer 1

Given:

Enthalpy of decomposition of NO2 = 33.84 kJ/mol

To determine:

Enthalpy change when 2.5 moles of NO2 decomposes

Step-by-step explanation:

The decomposition of NO2 is represented as:

2NO2(g) → N2(g) + 2O2(g)

Enthalpy change when 1 mole of NO2 decomposes is 33.84 kJ

therefore the enthalpy change corresponding to the decomposition of 2.50 moles of NO2 = 33.84 kJ * 2.40 moles/ 1 mole = 81.22 kJ

Ans: ΔH(decomposition) = 81.22 kJ

Answer 2

The enthalpy change when 2.50 mol of nitrogen dioxide decomposes is 84.6 kJ/mol.

Step-by-step explanation:

Enthalpy of the formation of
`NO_2=33.84 kJ/mol`

`(1)/(2)N_2+O_2\rightarrow NO_2,\Delta H_f=33.84 kJ/mol`

Enthalpy of decomposition when one mol of nitrogen-dioxide decomposes.

`NO_2\rightarrow (1)/(2)N_2+O_2,\Delta H_d=-33.84 kJ/mol`

When 1 mol of
`NO_2` decomposes it gives = -33.84 kJ/mol

When 2.50 mol of nitrogen-dioxide decomposes to give:

`2.5 * -33.84 kJ/mol=-84.6kJ/mol`

The enthalpy change when 2.50 mol of nitrogen dioxide decomposes is 84.6 kJ/mol.