The substances which are present at the starting of a chemical reaction are known as reactants. In the burning of natural gas, for example, methane (CH4) and oxygen (O2) are the reactants in the chemical reaction.
Water as a reactant in hydrolysis: The simplest chemical reaction in which a water molecule is a reactant is known as hydrolysis reaction. The word hydrolysis comes from the word hydro, which is Greek for water, and lysis, which means “to unbind.” In practical terms, hydrolysis means the act of separating chemicals by adding water.
In the process of hydrolysis, the pH of the solution can also be change because the reaction mostly takes place between water molecule and an ion. A bond present in a molecule splits with the help of H2O. This process would term as hydrolysis. A common hydrolysis takes place when a salt of weak acid and weak base is dissolved in water.
The general formula of a hydrolysis reaction is: AB + H2O > AH + BOH Water can also withstand a chemical change. Water molecules can be broken down into hydrogen and oxygen molecules by a chemical reaction called electrolysis. When an electric current is passed through liquid water (H2O), it changes the water into two gases—hydrogen and oxygen. The molecules of water break apart into individual atoms. These atoms then recombine into hydrogen molecules (H2) and oxygen molecules (O2). The original material (water) changes into different substances through a chemical reaction. Hydrogen and oxygen are used as rocket fuel for the space shuttle. During liftoff, liquid hydrogen and liquid oxygen are combined in a reaction that is the opposite of electrolysis. This reaction produces water and a large amount of energy that helps push the shuttle into orbit.
In simple wording, Water act as a reactant and it broke or we can say split the larger molecule in the smaller ones, The H and OH bonds are attached to the two products that are formed after the reaction.
Water as a reactant in photosynthesis:
Another process in which water is used as an important reactant is photosynthesis. In this process plants makes their own food by converting light energy into chemical energy. The products of photosynthesis, oxygen and glucose, are the reactants of the cellular respiration reaction. In turn, the products of cellular respiration, carbon dioxide and water, are the reactants in photosynthesis.
6CO2 + 6H2O + Light energy —> C6H12O6 + 6O2
In the green plants, photosynthesis is the main process which takes place. In this process water and carbon dioxide are reactants which break up and produce a glucose and oxygen molecule in order to make their own food for growth.
In the above reaction the carbon dioxide, water and light energy are converted into carbohydrate- glucose molecule and an oxygen molecule. The light is consumed by the green leaves in which the green pigment chlorophyll is present which helps and plays a major role in producing food and growth of the plant.
H2O, CO2 and sunlight these are the necessary components for a plant to do its photosynthesis process. When the water and carbon dioxide are converted into glucose product then it is converted into pyruvate which is the glycolysis –and further led to krebs cycle and ETC( electron transport chain). Water is the most important reactant in photosynthesis process because it makes food for plants and it is the basis of all food chains.
Water directly get involved as a reactant in many different metabolic reactions. It also get involved in unlike reactions happening in the body. It has the a vital role in many chemical reactions because mostly reactions occur in aqueous medium. It is also a solvent for most biochemical reactions. It is the main reactant and product of the reactions.