Chemical Equations

A chemical equation is a simplified representation of a chemical reaction. It represents the reactants, products, and their physical states symbolically. A balanced chemical equation contains an equal number of atoms of each type on the reactants and products sides of the equation.

If charged species are involved, the sum of the reactants’ charges should equal the sum of the products’ charges. No changes to the formulas of reactants or products are permitted during the balancing of a chemical equation. A balanced chemical equation adheres to the laws of mass conservation and constant proportions.

Reactants → Products

Chemical Equation Types

While the reactants, products, and reaction arrows are the three essential components of a chemical equation, many equations contain significantly more information.

Chemical Formulas: Chemical formulas are used to express reactants and products using element symbols and subscripts.

Chemical reactions are traditionally read from left to right. On the left hand side of the equation, the reactants are written. While drawing the chemical structures of the reactants is acceptable, the conventional method provides the chemical formulas for the reactants (e.g., H₂, O₂).

• The reaction’s products are indicated on the right side of the reaction arrow

• The reaction arrow indicates the direction in which the chemical reaction will proceed

• When more than one reactant or product occurs, a plus sign (+) is used to separate them

Coefficients:

Coefficients are numerical values added to the beginning of a chemical formula. They denote the chemical equations and stoichiometry of the reactants and products, allowing you to quickly determine their mole ratio in a balanced equation. For instance, in the formula 4H₂O₂, the coefficient is “4”. The number “1” is omitted by convention. As a result, you write O₂ rather than 1O₂. While coefficients are typically whole numbers, you may encounter equations that use fractions or decimal points.

Subscripts:

Following the element symbol in a chemical formula, subscripts indicate the number of atoms of that element in a compound. The “2” in H₂O, for example, is a subscript.

Not all chemical equations include information about the state of matter of the reactants and products. However, when a state of matter is specified, it is denoted by the chemical formula of the reactant or product enclosed in parentheses. The states of matter are denoted by the abbreviations (s) for solid, (l) for liquid, (g) for gas, and (aq) for species that are dissolved in an aqueous solution.

Chemical Equation with a Reaction Arrow

The nature of the reaction: The arrow indicates the direction of the chemical reaction:

The most frequently used reaction arrow points left to right. The symbol indicates that the reaction proceeds in a net forward direction, with reactants combining to form products.

Certain equations depict equilibrium. The symbol indicates that the reactants and products are in chemical equilibrium. The reaction occurs in both directions. This means that both sides of the equation act as reactants and products at the same time. If one of the arrows is shorter than the other, the longer arrow represents the primary direction in which the reaction occurs, whereas the shorter arrow indicates that the reaction occurs in this direction but is not preferred.

• The symbol indicates that the reaction occurs both forward and backward.

• Chemical equations and stoichiometry relationship is denoted by an equal sign or =. Chemical Equations That Are Unbalanced and Balanced

• Chemical equations can be asymmetrical or symmetrical.

An unbalanced chemical equation specifies the reactants and products, as well as the direction in which the reaction proceeds, but does not specify the mole ratio of reactants to products.

H₂ + O₂ = H₂O

A balanced chemical equation begins with coefficients and indicates the stoichiometric ratio of reactants to products. On both sides of the reaction arrow, a balanced chemical equation contains equal numbers and types of atoms. It is both mass and charge balanced.

Ionic Chemical Equations

Examples: 2H₂ + O₂ → 2H₂O

The net electrical charge on reactants and products is indicated by ionic chemical equations. The net electrical charge on both sides of the reaction arrow is equal in a balanced ionic equation.

For instance, 2Ag⁺(aq) + Cr₂O₇^–(aq) → Ag₂Cr₂O₇(s)

Take note that the coefficient is multiplied by the charge. In this example, the silver ion has two “+” charges and the chromate ion has two “-” charges. These charges cancel one another out, leaving the reactants with a net neutral charge [2(+1) + 1(-2) = 0]. Silver chromate is an electrically neutral substance.

CHEMICAL REACTIONS

Chemical reactions occur when reactants (substances involved in the reaction) react to form products (new substances that are produced as a result of the reaction). A reorganisation of atoms occurs during the process that results in the formation of products with novel properties. Fermentation of milk, formation of curd, and cooking of grapes. Chemical reactions occur during the digestion of food, the process of respiration, the combustion of fuels, the rusting of iron, and the ripening of fruits.

Chemical Reaction Characteristics

Chemical reactions frequently exhibit observable characteristics. The critical characteristics of chemical reactions include the following:

• The evolution of carbon dioxide gas is a characteristic of the reaction between sodium carbonate and dilute hydrochloric acid

• Precipitate formation- When sulphuric acid and barium chloride react, a white precipitate of barium sulphate is formed

• The colour of sulphur dioxide gas changes from orange to green when it passes through an acidified solution of potassium dichromate

• Temperature change- When quicklime (calcium oxide) reacts with water to form slaked lime (calcium hydroxide), a temperature increase occurs, Exothermic reactions are those that generate heat. When carbon dioxide reacts with oxygen in the air to form carbon dioxide, a large amount of heat is released. Temperature decrease occurs as a result of the reaction between barium hydroxide and ammonium chloride, which produces barium chloride, water, and ammonia. Endothermic reactions are those that absorb heat

• When wax (solid) is burned in the form of a candle, it transforms into water (liquid) and carbon dioxide (gas)

• Certain chemical reactions exhibit two or more of these characteristics

Types of Chemical Reactions

The product formed, the changes that occur, the reactants involved, and so forth serve as the basis for various types of Chemical Reactions. Numerous types of Chemical Reactions

 exist.

• Combustion reaction

• Decomposition reaction

• Neutralisation reaction

• Redox Reaction

• Precipitation or Double-Displacement Reaction

• Synthesis reaction