Answer :
The answer is 3. The releasing of energy means exothermic reaction. So the ΔH should be negative. And the greatest quantity of energy released means that the greatest number. So according to the table I, the answer is 3.
Answer:
3. N2(g) +3H2(g)->2NH3(g)
Explanation:
Reactions can be broadly classified as endothermic and exothermic reactions. In the former, energy or heat is absorbed by the reactants and the enthalpy change of the reaction is positive. In the later, heat is released ans the enthalpy change of the reaction is negative.
For the given reactions, the enthalpy change or ΔH values are:
1. 2C(s) + 2H2(g) -> C2H4(g) ΔH = +52.4 kJ
2. 2C(s)+3H2(g) -> C2H6(g) ΔH = -84 kj
3. N2(g) +3H2(g)->2NH3(g) ΔH = -91.8 kJ
4. N2(g)+O2(g) -> 2NO(g) ΔH = +182.6 kJ
Reactions 1 and 4 are endothermic while reactions 2 and 3 are exothermic in which heat is released.
More negative the ΔH value, greater is the amount of heat released.
Thus, reaction 3, represents a change resulting in the greatest quantity of energy released
