Question

Hydrogen peroxide is placed in sunlight and reacts slowly to form oxygen and water.

a. Rewrite the chemical reaction as a word equation

b. State the evidence that a chemical reaction has occurred

c. Is the reaction exothermic or endothermic? Explain your reasoning

Answer 1

Hydrogen peroxide undergoes a chemical reaction to form water and oxygen. The evidence for a chemical reaction includes the formation of new products and any accompanying physical changes. The reaction is exothermic, releasing heat energy during the process.

Step-by-step explanation:

An example of a simple chemical reaction is the breaking down of hydrogen peroxide molecules, each of which consists of two hydrogen atoms bonded to two oxygen atoms (H₂O₂). The reactant hydrogen peroxide is broken down into water, containing one oxygen atom bound to two hydrogen atoms (H₂O), and oxygen, which consists of two bonded oxygen atoms (O₂). In the equation below, the reaction includes two hydrogen peroxide molecules and two water molecules. This is an example of a balanced chemical equation, wherein the number of atoms of each element is the same on each side of the equation. According to the law of conservation of matter, the number of atoms before and after a chemical reaction should be equal, such that no atoms are, under normal circumstances, created or destroyed.

2H₂O₂ (hydrogen peroxide) → 2H₂O (water) + O₂ (oxygen)

The evidence that a chemical reaction has occurred in this case can be observed by the formation of oxygen gas (O₂) and water (H₂O). The production of gas and the change in the composition of the reactants to form new products are indications of a chemical change. Additionally, the observation of any physical changes, such as color change, temperature change, or formation of a precipitate, can also be evidence of a chemical reaction.

The reaction of hydrogen peroxide to form oxygen and water is an exothermic reaction. This means that it releases energy in the form of heat. When the chemical bonds in hydrogen peroxide are broken and new bonds are formed in the resulting products, energy is released. In this case, the energy released as heat is given off to the surroundings, making the reaction exothermic. The reaction can also be considered exothermic because it is spontaneous and occurs without the need for an external energy source.

Answer 2

a. The chemical reaction can be rewritten as a word equation as follows:

Hydrogen Peroxide -> Oxygen + Water

b. Evidence that a chemical reaction has occurred includes the production of a new substance (oxygen and water), a change in the physical properties of the reactants (change in color, odor, or temperature), and the release of energy (evolution of oxygen gas).

c. The reaction is likely exothermic, which means it releases energy. This is because the reaction produces new substances (oxygen and water) and releases energy in the form of oxygen gas. In an endothermic reaction, the reactants would absorb energy from the surroundings.