Which statement best describes the difference between endothermic and exothermic reactions?

they are opposites because endothermic reactions require energy and exothermic reactions release energy.
they are opposites because endothermic reactions release energy and exothermic reactions require energy.
they the same because they are both ways of forming precipitates.
they the same because they are both ways of forming gasses.

The correct answer would be "They are opposites because endothermic reactions require energy and exothermic reactions release energy".

Endothermic reactions are those in which energy is given consumed. The energy can be absorbed in the form of heat, light or sound. They are characterized by an increase in enthalpy or positive heat flow that is, into the reaction.

The simplest example can be a photosynthesis. It uses energy in from of sunlight to convert carbon dioxide and water into glucose and oxygen.

Other example may include formation of nitric oxide.

O₂ + N₂ + energy → 2NO

The energy is obtained from automobiles exhaust.

In contrast, exothermic reaction are those in which energy is liberated out in the form of heat, light or sound. Enthaly is decreased in these reactions. Oxidation reactions are generally exothermic in nature.

For example, cellular respiration (oxidation of glucose to produce ATP).

Glucose + oxygen → carbon dioxide + water + energy (ATP)

A) They are opposites because endothermic reactions require energy and exothermic reactions release energy.

a tetrad is the foursome during meiosis made by two homologous chromosomes that have each already replicated into a pair of sister chromatids.

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