Calculation of Valency

Chemical reactions and equations are an integral part of understanding Chemistry. They act as one of the building blocks of this field and play a very important part in Chemistry. Let us read more about what chemical reactions are and how chemical equations can be used to represent reactions. 

What is a Chemical Reaction?

A chemical reaction is one of the basic building blocks of Chemistry. It refers to the process of converting one or more reactants into one or more products under specific conditions of temperature and pressure and in the presence or absence of promoters known as catalysts. The reactants and products can be molecules or compounds. 

What is Chemical Equation?

In Chemistry, we often represent chemical reactions using only symbols of the particular elements and indicate the quantity of each substance using a quantity known as moles, for both the reactants and the products. This manner of representing a chemical reaction is known as a chemical equation. 

Parts of a Chemical Equation

The main parts of a chemical equation are the reactants, usually written on the right side and products, generally written on the left side of the equation. They are usually separated by a , which is read aloud as ‘yields’. If there are more than one reactant or product, then they are separated by a +. The state of matter of each of the reactants and products is written as a subscript in parentheses just beside the compound or molecule as a subscript. Solids are represented with (s), liquid by (l) and gases by (g). If a liquid is produced by mixing the compound or molecule in water, it is said to be a aqueous solution and is represented by (aq),

Let us take the example of burning of methane gas.

HCl(l)+NaOH(l) NaCl(s)+H2O(l)

Some reactions often give out energy in the form of heat, and this heat is represented with a delta (Δ) on the product side. If the reaction proceeds when the reactants are heated, then delta (Δ) is written over the arrow separating the reactants and the products. → indicates that the forward reaction is favoured while ← indicates that the reaction conditions favour the reverse reaction. ⇌ or ↔ indicates that the reaction is in equilibrium condition and the rate of forward and backward reaction is the same.

Factors Affecting a Chemical Reaction

The main factors that affect a chemical reaction are the temperature, physical state of reactants, reactant concentration and the presence of catalysts. Let us see how each of these factors affects a chemical reaction. 

Temperature

The rate of reaction would usually increase with the increase in temperature. An increased temperature increases the kinetic energy of the individual particles and increases the number of collisions between them. This results in a higher rate of reaction as compared to lower temperatures. 

Physical State of Reactants

The physical state of reactants has a major impact on the rate of reaction that takes place. For more fluid states like liquid or gases, the surface area is greater and more molecules come in contact with each other. Hence, the rate of reaction is high if the reactants are two gases. On the other hand, if both reactants are solid, they will only react on the surface and the process would be incomplete. This can be evident from the example of rusting of iron. Usually, only the surface of iron rusts, while the insides remain untouched for a long time. 

Reactant Concentration

Usually, the higher the concentration of reactant, the higher the rate of reaction is. For the reactant with a higher concentration, more collisions will take place for that reactant, hence promoting the rate of reaction. 

Presence of Catalysts

Catalysts are chemical compounds or elements that increase or reduce the rate of the reaction, without getting involved in the reaction themselves. Some reactions are extremely slow and need to be made faster with the use of catalysts. However, there are also some reactions that are too fast to be observed properly. In these cases, a catalyst which reduces the rate of reaction is used. Hence, the rate of reaction is determined by the kind of catalyst used. There are many reactions which do not need a catalyst to promote reactivity.

Conclusion

You now have basic knowledge about chemical reactions and equations. This is the building block of Chemistry and would help you understand more advanced concepts which involve the use of particular reactions. Furthermore, you would be able to easily understand and work on related concepts like balancing equations, which will be necessary for further understanding and application of Chemistry.