A measure of thermal energy transferred between two different bodies at different temperatures would be the correct answer. So, the third option.
Answer:
Endothermic reaction chemical equation
Reactnt A + Reactant B + Heat (energy) ⇒ Products
Exothermic reaction chemical equation
Reactnt A + Reactant B ⇒ Products + Heat (energy)
Explanation:
Endothermic Reaction
An endothermic reaction is a reaction that reaction that requires heat before it would take place resulting in the absorption of heat from the surrounding that can be sensed by the coolness of the reacting system
An example of an endothermic reaction is a chemical cold pack that becomes cold when the chemical and water inside it reacts
Exothermic Reaction
An exothermic reaction is one that rekeases energy to the surroundings when it takes place. This is as a result of the fact that the combined heat energy of the reactants is more than the chemical heat energy of the products. An example of an exothermic reaction is a burning candle
Reduction half reaction: Cu²⁺(aq) + 2e⁻ → Cu⁰(s).
Oxidation half reaction: NO₂⁻(aq) + H₂O(l) → NO₃⁻(aq) + 2H⁺(aq) + 2e⁻.
Balanced chemical reaction:
Cu²⁺(aq) + NO₂⁻(aq) + H₂O(l) → Cu(s) + NO₃⁻(aq) + 2H⁺(aq).
Copper is reduced from oxidation number +2 (Cu²⁺) to oxidation number 0 (Cu) and nitrogen is oxidized from oxidation number +3 (in NO₂⁻) to oxidation number +5 (in NO₃⁻).
