Chemical Reaction

Unit: 15

Book Icon Class 10: Science

Chemical Reaction, Reactants and Products, Chemical Equation, Types of Chemical Reaction, Rate of Chemical Reaction, Factors Affecting Rate of Chemical Reaction, Catalyst

Chemical Reaction

The exchanges, combination, or decomposition that occurs in the molecules of substances during a chemical change is called chemical Reaction. The chemical change transforms one substance into another completely new.

Reactants and Products

The substances that take part in the chemical reaction are called Reactants.

The substances produced after the chemical change are called Products.

Example:

\( \begin{aligned} & \text{Magnesium}(Mg) + \text{Oxygen}(O_2) \rightarrow \text{Magnesium Oxide}(MgO_2) \\ \end{aligned} \)

Reactants : Magnesium(Mg) + Oxygen(O₂)

Products : Magnesium Oxide(MgO)

Chemical Equation

The equation which represents the chemical change is called the chemical equation. While writing chemical equations we can use words, symbols, or molecular formulae. If we use words in a chemical equation, then it is called a word equation. And if we use symbols in a chemical equation, then it is called a formula equation.

Example:

Word Equation

\( \begin{aligned} & \text{Zinc} + \text{Hydrochloric Acid} \rightarrow \text{Zinc Chloride} + \text{Hydrogen} \\ \end{aligned} \)

Formula Equation

\( \begin{aligned} & Zn + HCl \rightarrow ZnCl_2 + H_2 \\ \end{aligned} \)

Types of Chemical Reactions

There are different types of chemical reactions. Some of them are discussed below.

1. Combination Reaction

The chemical reaction in which two or more than two substances combine to produce a new substance is called a Combination Reaction.

Example:

\( \begin{aligned} & H_2 + O_2 \rightarrow H_2O \\ \end{aligned} \)

2. Decomposition Reaction

The chemical reaction in which a substance decomposes into two or more than two substances is called a Decomposition Reaction.

Example:

\( \begin{aligned} & CaCO_3 \rightarrow CaO + CO_2 \end{aligned} \)

3. Single Displacement Reaction

The chemical reaction in which an element or a radical of a compound is displaced by another element or radical is called a single displacement reaction.

Example:

\(\begin{aligned} & Zn + HCl \rightarrow ZnCl_2 + H_2 \end{aligned} \)

4. Double Displacement Reaction

The chemical reaction in which an element or a radical of a compound is mutually displaced by another element or radical is called a double displacement reaction.

Example:

\( \begin{aligned} & HCl + NaOH \rightarrow NaCl + H_2O \end{aligned} \)

5. Acid Base Reaction

The chemical reaction in which an acid reacts with a base to produce salt and water is called an acid-base reaction. It is also called Neutralization Reaction.

Example:

\( \begin{aligned} & NaOH + HCl \rightarrow NaCl + H_2O \\ \end{aligned} \)

Rate of Chemical Reaction

The time taken to complete the reaction is called the rate of chemical reaction.

Factors Affecting the Rate of Chemical Reaction

Various factors affect the chemical reactions. Some of these factors are as follows:

Temperature, Pressure, Surface Area, Light, Catalyst, Concentration

Catalyst

The chemical compound which affects the rate of a chemical reaction is called a catalyst. The catalyst does not take part in the reaction. The catalyst can be divided into two types viz., Positive Catalyst and Negative Catalyst.

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