Question

Which of the reactions are exothermic?

A. 2Mg(s)+O₂(g)⟶2MgO(s)+heat2Mg(s)+O₂(g) ⟶2MgO(s)+heat

B. NH₃(g)+HCl(g)⟶NH₄Cl(s)+heatNH₃(g)+ HCl(g)⟶NH₄Cl(s)+heat

C. AgCl(s)+heat⟶Ag+(aq)+Cl (aq)AgCl(s)+heat⟶Ag+(aq)+Cl−(aq)

Answer 1

Reactions A (2Mg(s) + O2(g) → 2MgO(s) + heat) and B (NH3(g) + HCl(g) → NH4Cl(s) + heat) are exothermic because they release heat. Reaction C (AgCl(s) + heat → Ag+(aq) + Cl−(aq)) is endothermic, requiring heat input. The correct exothermic options are A and B.

Step-by-step explanation:

In the context of thermodynamics, an exothermic reaction is a chemical reaction that releases energy in the form of heat to its surroundings. This contrasts with endothermic reactions, which absorb energy.

To determine if a reaction is exothermic, look for a release of heat as indicated in the reaction equation or a negative enthalpy change (ΔH).

Let's evaluate the given reactions:

1. 2Mg(s) + O2(g) → 2MgO(s) + heat is an exothermic reaction because it shows the release of heat.
2. NH3(g) + HCl(g) → NH4Cl(s) + heat is also an exothermic reaction because it also indicates the release of heat.
3. AgCl(s) + heat → Ag+(aq) + Cl−(aq) is an endothermic reaction because it requires an input of heat for the reaction to occur.

The exothermic reactions are A. 2Mg(s) + O2(g) → 2MgO(s) + heat and B. NH3(g) + HCl(g) → NH4Cl(s) + heat. These are the reactions where heat is a product, signifying that energy is being released into the surrounding environment.

Thus, the correct option in the final answer for the exothermic reactions is option A and B.