A Simple Note On Chemical Reactivity

Chemical reactions are a significant part of technology, pharmaceuticals and life itself. Burning fuels, smelting iron, producing glass and pottery, brewing beer, and making wine and cheese are just a few of the numerous activities that involve chemical reactions that have been recognized and deployed for thousands of years.

A chemical reaction is a process that converts one or more compounds, known as reactants, to one or more distinct substances, known as products. Chemical elements and compounds are both types of substances. A chemical reaction reconfigures the basic atoms of the reactants, resulting in the formation of various substances as products.

Chemical reactivity

• The reactivity of a material in chemistry is a measure of how easily it conducts a chemical reaction. The material might be involved in the reaction alone or in combination with other atoms or compounds, and it is usually followed by a release of energy.
• The most reactive elements and compounds are capable of spontaneous or explosive ignition. They typically burn in both water and oxygen in the air.
• The temperature influences reactivity. Increasing the temperature makes more energy available for a chemical reaction, which typically increases its likelihood.
• The physical qualities of a sample, its chemical purity, and the presence of additional chemicals all have an impact on its reactivity.
• Simply put, reactivity is determined by the context in which a chemical is observed. Baking soda and water, for example, are not especially reactive, but baking soda and vinegar easily react to produce carbon dioxide gas and sodium acetate.
• The periodic table’s structure enables reactivity predictions. Both strongly electropositive and very electronegative materials have a great proclivity for reaction.
• These elements may be found in the periodic table’s top right and lower left corners.

Concepts of chemical reactions

• Chemical reactions solely affect the locations of electrons in the formation and breaking of chemical bonds between atoms, without any change to the nuclei, and may be represented using a chemical equation.
• New substances are produced during a chemical reaction. For this to happen, the chemical bonds of the chemicals break, and the atoms that make up the substances split and reorganise themselves into new compounds with new chemical bonds. This is referred to as a chemical reaction 
• Atoms are never formed or destroyed during chemical processes. The same atoms that exist in the reactants are also found in the products; they are simply rearranged in different sequences.

Types of chemical reactions

There are various types of chemical reactions with more than one way to classify them. Here are a few common reactions:

Oxidation-Reduction or Redox Reaction

Oxidation refers to the whole or partial loss of electrons or acquisition of oxygen. Reduction refers to the entire or partial gain of electrons or loss of oxygen. A redox reaction is another word for an oxidation-reduction process.

The oxidation numbers of atoms are altered during a redox process. Electrons can be transferred between chemical species during redox reactions.

Example: –

2 S₂O₂²⁻(aq) + I₂(aq) → S₄O₆²⁻(aq) + 2 I−(aq)

Above example of a redox reaction is the process that occurs when I2 is reduced to I– and S₂O₃²⁻ (thiosulfate anion) is oxidised to S₄O₆²⁻.

Direct Combination or Synthesis Reaction

In a direct combination or synthesis reaction, two or more chemical species unite to generate a more complex product.

X + Y → XY

Example: 

The reaction of iron with sulphur to produce iron (II) sulphide

8 Fe + S₈ → 8 FeS

Chemical Decomposition or Analysis Reaction

A decomposition reaction occurs when a more complex material decomposes into its simpler constituents.

AB → A + B

Example

The electrolysis of water into oxygen and hydrogen gas 

2 H₂O → 2 H₂ + O₂

Single Displacement or Substitution Reaction

One element is displaced from a compound by another element in a substitution or single displacement process.

A + BC → AC + B

Example

Zn + 2 HCl → ZnCl₂ + H₂

In this reaction, hydrogen is replaced by zinc.

Metathesis or Double Displacement Reaction

In a double displacement or metathesis process, two chemicals swap bonds or ions to generate new molecules.

AB + CD → AD + CB

Example

NaCl(aq) + AgNO₃(aq) → NaNO₃(aq) + AgCl(s)

The above reaction between sodium chloride and silver nitrate leads to the formation of sodium nitrate and silver chloride.

Acid-Base Reaction

An acid-base reaction is a sort of double displacement reaction that occurs when an acid and a base come into contact with each other. The acid’s H+ ion combines with the base’s OH– ion to generate water and an ionic salt.

HA + BOH → H₂O + BA

Example –

The reaction that takes place between hydrobromic acid (HBr) and sodium hydroxide 

HBr + NaOH → NaBr + H₂O

Chemical equations

A chemical equation is a written description of the process that occurs during a chemical reaction. It is written with the use of numbers and symbols.

In a chemical equation, the reactant elements are put on the left-hand side and the product elements are placed on the right-hand side, with a plus sign between the entities in both the reactants and the products and an arrow pointing towards the products that indicate the direction of the reaction.

An example of a chemical equation is:

2 HCl + 2 Na → 2 NaCl + H₂

According to this equation, sodium and HCl combine to generate NaCl and H₂. It also implies that two sodium molecules are required for every two hydrochloric acid molecules, and the reaction will produce two sodium chloride molecules and one diatomic molecule of hydrogen gas for every two hydrochloric acid molecules and two sodium molecules that react.

Conclusion

New substances are generated as a result of chemical reactions. For this, the chemical bonds of the substances break, and the atoms that make up the substances split and reorganise themselves into new compounds with new chemical bonds.