Select all of the following reactions that are endothermic. ½N 2(g) + 3/2H 2(g) → NH 3(g) + 11.0 kcal/mole
H 2(g) + ½O 2(g) → H 2O(g), ΔH = -57.83 kcal/mole
½N 2(g) + O 2(g) + 8.1 kcal → NO 2(g)
½N 2(g) + ½O 2(g) → NO(g), ΔH = +21.6 kcal/mole
NH 3(g) → ½N 2(g) + 3/2H 2(g), ΔH = +11.0 kcal/mole

½N 2(g) + O 2(g) + 8.1 kcal → NO 2(g)

½N 2(g) + ½O 2(g) → NO(g), ΔH = +21.6 kcal/mole

NH 3(g) → ½N 2(g) + 3/2H 2(g), ΔH = +11.0 kcal/mole

General Formulas and Concepts:

Thermochemistry

Explanation:

An endothermic reaction would have heat or energy gained in the final stage of the reaction.

This means that our enthalpy would be positive and heat/energy would be added as a reactant.

Out of all the answer choices, we see that only these have heat/energy added in the reactant side or the enthalpy being positive:

½N 2(g) + O 2(g) + 8.1 kcal → NO 2(g)

½N 2(g) + ½O 2(g) → NO(g), ΔH = +21.6 kcal/mole

NH 3(g) → ½N 2(g) + 3/2H 2(g), ΔH = +11.0 kcal/mole

Topic: AP Chemistry

Unit: Thermochemistry

answer: - 3.) the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

solution: - as per the rules, oxidation number of oxygen in its compounds is -2. the sum of oxidation numbers of all the elements of a molecule or compound is zero.

also, the oxidation number in elemental form is zero.

in no, the oxidation number of o is -2 so the oxidation number of n is +2 so that the sum is zero.

similarly, the oxidation number of c in co is +2 and o is -2.

on product side the oxidation number of n is 0 as it is in the elemental form() .

oxidation number of c in carbon dioxide is +4 as there are two oxygen in it and we know that each oxygen is -2.

so, oxidation number of n is changing from +2 to 0 and the oxidation number of c is changing from +2 to +4.

since nitrogen is reduced and hence no is acting as an oxidizing agent. carbon is oxidized and so co is acting as a reducing agent.

so, the right choice is number 3.)the oxidation state of nitrogen in no changes from +2 to 0, and the oxidation state of carbon in co changes from +2 to +4 as the reaction proceeds.

2b2t

explanation:

2b2t