1. \( \mathrm{H}_{2}+\longrightarrow \mathrm{O}_{2} \longrightarrow \xrightarrow{2} \mathrm{H}_{2} \mathrm{O} \)

The reaction depicted is a fundamental chemical process where hydrogen (\(\mathrm{H}_{2}\)) reacts with oxygen (\(\mathrm{O}_{2}\)) to form water (\(\mathrm{H}_{2}\mathrm{O}\)). This is widely known as combustion, and in its simplest form, it’s the basis of how hydrogen fuel cells generate energy, producing only water as a by-product. This reaction is not only critical for understanding energy production but also highlights the importance of hydrogen as a clean energy source. In the real world, the reaction can be witnessed in various situations, from the combustion in engines to the natural processes in cells where hydrogen and oxygen interact to produce energy in the form of ATP. Additionally, this reaction is utilized in hydrogen-powered vehicles, showcasing its relevance in modern technology and the push towards sustainable energy solutions. So, the next time you enjoy a drop of water, remember the journey of hydrogen and oxygen coming together to make that happen!