Chemical Equations

Chemical Equations

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Chemical equations are symbolic representations of chemical processes in which the reactants and products are expressed in terms of their chemical formulae. They also utilize symbols to express aspects such as response direction and the physical properties of the responding entities. In 1615, the French chemist Jean Beguin developed the first chemical equations.

Chemical reactions can be expressed on paper using chemical equations, for example; the reaction between hydrogen gas and oxygen gas to form water.

2H2 + O2 → 2H2O

In the preceding example, the responding entities are written on the left-hand side of the chemical equation, but the products of the chemical reactions are written on the right-hand side. It can also be seen that each of the symbols for the associated reactants and products has a coefficient assigned to it. The coefficients of entities in a chemical equation are the exact value of that entity’s stoichiometric number.

Representing the Chemical Reaction’s Direction

One of the four symbols can be used to distinguish the reactants and products (for which the chemical formulas are stated in chemical equations).

• The sign ‘→’ is used to represent a net forward response.
• The symbol ‘⇋’ is used to represent a condition of chemical equilibrium.
• The ‘=’ sign is used to express stoichiometric relationships.
• The sign ‘⇆’ is used to denote a response that happens in both forward and backward directions.
• Multiple entities on each side of the reaction symbols described above are separated from each other in a chemical equation by the ‘+’ sign.
• When employed in a chemical equation, the ‘→’ symbol is commonly interpreted as ‘gives rise to’ or ‘yields.’

Representing the Physical States of the Entities Reacting

Aside from the stoichiometric coefficients of the responding and generated entities, symbols enclosed in parenthesis are written adjacent to them to describe their physical states during the chemical reaction. These symbols might be any of the ones listed below.

• The symbol (s) represents a solid-state entity.
• The sign (g) indicates that the entity is gaseous.
• The symbol (l) represents an entity’s liquid condition.
• The (aq) sign represents an aqueous solution of the entity represented by the (aq) symbol in a chemical equation.
• In some reactions, a reactant or a product may exist as a precipitate that is insoluble in the solution in which the reaction is taking place. To describe these things as precipitates, the ‘↓’ symbol is used next to their chemical formulas.

Energy Input representation in a Chemical Equation

• Some chemical processes require an energy input to progress. The energy needs of these reactions are stated in their respective chemical equations above the arrow symbol (ahead reaction) using the symbols shown below.
• The Greek letter delta (Δ) in its uppercase form is used to indicate that the reaction requires an input of heat energy.
• The formula ‘hv,’ which represents photon energy, is used above the arrow sign to indicate that the reaction requires an input of light to continue.
• It is vital to note that the stoichiometric coefficients assigned to each entity in the chemical equation are utilized to ensure that the entire equation obeys the laws of charge conservation and mass conservation.
• Balanced Chemical Equation: A balanced chemical equation contains the same number of atoms on both sides.

For instance, Zn + H2SO4 → ZnSO4 + H2

Because the numbers of zinc, hydrogen, and sulfate are equal on both sides of this equation, it is a Balanced Chemical Equation.

Mass cannot be generated or destroyed in a chemical process, according to the Law of Conservation of Mass. To be in accordance with this law, the total mass of elements present in reactants must match the total amount of elements present in products.

• Unbalanced Chemical Equation: If the number of atoms of each element in the reactants does not equal the number of atoms of each element in the product, the chemical equation is said to be unbalanced.

For instance, Fe + H2O → Fe3O4 + H2

In this case, the amount of atoms of elements on both sides of the reaction is not equal. For example, on the left-hand side, there is just one iron atom, but three iron atoms are present on the right-hand side. As a result, the chemical equation is imbalanced.

Examples of Chemical Equations

A few examples of chemical equations:

• H3PO4 + 3KOH → K3PO4 + 3H2O
• Na2S + 2AgI → 2NaI + Ag2S
• PCl5 + 4H2O → H3PO4 + 5HCl

Ionic Chemical Equations

Electrolytes (substances that break down into ions when dissolved in polar liquids) are separated and expressed as individual ions in ionic chemical equations. These equations are extremely useful for explaining single displacement reactions as well as salt metathesis processes (generally referred to as double displacement reactions).

Example: Chemical Equation: CaCl2 + 2AgNO3 → Ca(NO3)2 + 2AgCl↓

Ionic Equation: Ca2+ + 2Cl + 2Ag+ + 2NO3 → Ca2+ + 2NO3 + 2AgCl↓

When the reactants and products of the ionic equation and the chemical equation are compared, the Ca2+ (calcium ion) and NO3 (nitrate) ions may be found on both sides of the ionic equation. Because they do not participate in the chemical process, these ions are referred to as spectator ions.

The net ionic equation for the above example may be stated by omitting the spectator ions and simply expressing the reaction between the participating ions, as shown below.

2Cl + 2Ag+ → 2AgCl↓

This ionic chemical equation may be translated as follows: two chloride ions derived from calcium chloride react with two silver cations derived from silver nitrate, resulting in a precipitate of silver chloride as the product.

Chemical Equations Frequently Ask Questions (FAQ’s)

What exactly are Chemical Equations?

They are equations that express chemical processes using chemical formulas and symbols. The reactants are represented on the left side of a chemical equation, while the products are shown on the right. These things are separated by a symbol that represents the reaction's direction. Each reactive entity is also allocated a stoichiometric coefficient.

What exactly is an ionic equation?

The chemical equations in which electrolytes are represented as dissociated ions are known as ionic equations. They are frequently used to depict the displacement processes in aqueous media. Some ions engage in these processes, whereas others do not. Ions that do not react are known as spectator ions and are often excluded from the net ionic equation.

Q. What are the four symbols used in these equations to represent physical states?

ANS: The following symbols are used to represent the physical states of the responding entities:

• (s) stands for solid.
• (l) stands for liquid.
• (g) stands for gas.
• A chemical’s aqueous solution is frequently represented by the symbol (aq).

Also Check

Important Topic Of Chemistry: Chemical Reactions

Chemical Reactions and Equations Class 10 Notes Science Chapter 1

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