Chemical Reactions and equations


A chemical reaction is the result of interaction between the 2 or more reactants resulting in the formation of the products. In a chemical reaction, all the reactants are written on the left-hand side of the equation and the products fall under the right-hand side followed by an arrow mark. There are many chemical reactions taking place within and outside of our bodies. A simple example is the process of digestion where the enzymes, water, food material combine to produce nutrients that can enter the bloodstream. A chemical reaction is characterised by a few changes such as the change in the colour and state of the substances with or without heat energy. In some reactions, we can observe the release of gas along with the evolution of light or sound.

Table of Content

1. Introduction

2. 3. Chemical Equations

4. Balancing of Chemical Equations

5. Guidelines used in balancing chemical equations

6. The stoichiometry of Chemical Reactions


Chemical Equations

A typical way of describing a chemical reaction is by writing a chemical equation. Writing equations using chemical formulas can help us to communicate effectively about the underlying details. A chemical equation is nothing but the symbolic representation of a chemical reaction in the form of symbols and formulae.


Balancing of Chemical Equations

Balancing of chemical equations refers to the process of ensuring that the number of each atom of the reactants is equally corresponding with the number of atoms of the products in a given chemical equation. A chemical equation can be considered to be correct only if there is a balance between the atoms of the left-hand side with that of the right-hand side. 


Guidelines used in balancing chemical equations

  1. Ensure that the chemical equation is correctly written in words. For example:

    1. Magnesium + Oxygen gas ----------->Magnesium Oxide

  2. Introduce the correct chemical formula in a symbolic fashion for the reaction written in the previous step. Remember, the atoms must be balanced between the 2 sides.

    1. Mg + O2-----------> MgO (Not Balanced)   

  3. Now, inspect the LHS (reactants) and the RHS (products) to check whether both of them have an equal number of atoms of the corresponding element.

  4. In case it is not equal, try to multiply the resultant chemical formula containing the unbalanced atoms by the LCM. For example, multiply by 2 for our case in the equation.

    1. 2Mg + O2 ----------->  2MgO   .

    2. During balancing of the chemical equation, always ensure that both the reactants and products retain their chemical formula.

  5. Very important, indicate the appropriate physical states of both the reactants and the products in a given chemical equation. For instance, solids are represented by (s), liquid (l), gases (g) and solutions / aqueous substances (aq).

 Hence,  2Mg(s) + O2 (g)    -----------> 2MgO(s) is a balanced chemical equation.


 The stoichiometry of Chemical Reactions

In chemistry, we can write chemical reactions either by word equations or through chemical equations. A stoichiometry equation is a chemical equation in which reactants combine in proportions to form products. Stoichiometry can, therefore, be defined as the amount of reactants required or the products produced in a chemical reaction. For instance,  2NaOH (aq) + H2S (aq)-----------> Na2S (aq) + 2H2O (l). Where two moles of NaOH reacts with one mole of H2S to give 1 mole of Na2S and 2 moles of H2O molecules. Both one and two are referred to as the stoichiometry coefficient. In the above chemical reaction, this coefficient shows the exact number of moles that took part in the reaction. In summary, the mass of an element, its number of moles and the number of molecules are used interchangeably.





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