Question

select the word(s) to complete the word equation that matches the description of the reaction. electrolysis breaks down water to form hydrogen and oxygen gas. the word equation that represents this reaction is: water → a bright light is produced when magnesium reacts with the oxygen in air to form magnesium oxide. the word equation that represents this reaction is: magnesium + oxygen → when methane burns, it reacts with oxygen to produce water and carbon dioxide. the word equation that represents this reaction is: methane + oxygen → done

Explanation:

First Reaction (Electrolysis of Water)

In the electrolysis of water, water ($\ce{H2O}$) is decomposed into its constituent elements, hydrogen ($\ce{H2}$) and oxygen ($\ce{O2}$) gases. So the products are hydrogen and oxygen.

Magnesium ($\ce{Mg}$) reacts with oxygen ($\ce{O2}$) to form magnesium oxide ($\ce{MgO}$). This is a synthesis reaction where two substances combine to form a single product.

Methane ($\ce{CH4}$) burns in oxygen ($\ce{O2}$) to produce water ($\ce{H2O}$) and carbon dioxide ($\ce{CO2}$). This is a combustion reaction, and the products are water and carbon dioxide.

Answer:

hydrogen + oxygen

Second Reaction (Reaction of Magnesium with Oxygen)