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# Chemical Reactions and Equations

Grade 10
May 6, 2023

## How to Balance a Chemical Equation

### Chemical Reaction:

The chemical changes of two or more chemicals at a time are called chemical reactions. The chemical reaction can be represented by the equation. The word equation represents the chemical words, the initial substances, and the final ones after the chemical reaction, separated by the arrow mark.

### Chemical Equation:

A chemical equation is a symbolic representation of the reactants and products of a chemical reaction. The initial chemicals before the reaction are called the reactants, and the chemicals after the reaction are called the products.

The number written in front of the chemical name is called the coefficient, and the number that is written after the chemical symbol in small is called the subscript. For example, in the above chemical equation, the chemicals HCl and Na are called the reactants, and the chemicals NaCl and H are the products.

### Skeleton Equation:

A chemical equation with an unequal number of atoms present on the reactants side and products side is called a skeleton equation.

Fe  +  O2    →    Fe2O3

In the reactants part, we see there is only one iron atom and two oxygen atoms, but in the product part, we see there are two iron atoms and three oxygen atoms. So the equation is not balanced.

### What is a Balanced Equation?

A chemical equation with an equal number of atoms present on the reactants side and products side is called a balanced equation. The balanced equation is also called a stoichiometric equation.

Example:

Take the example of forming the water molecule from the hydrogen and oxygen atoms. The equation is as follows:

2H2 + O2     →     2H2O

### Law of Conservation of Mass:

The law of conservation of mass needs to be kept in mind while balancing the equation. According to the law of conservation of mass, the mass of reactants and products are to be equal, and balancing is done as per the law. According to the law of conservation of mass, mass can neither be created nor destroyed but can be converted from one form to another.

### Characteristics of the Balanced Equation:

The balanced equation gives the number of participating reactants and products exactly. Balanced equations possess substances so that the total charge on the left hand and right hand is balanced.

## Stoichiometric Coefficients:

The number of times each reactant is reacting and the number of times each product is appearing in a balanced equation are said to be stoichiometric coefficients.

Step 3: We should always choose a compound with a maximum number of atoms in it, either on the reactants side or the products side.

Fe + H2O → Fe3O4 + H2

Here we select Fe3O4, which contains four oxygen atoms on the right-hand side.

We cannot make H2O to H2O4 to increase oxygen atoms, so we make it 4H2O.

Fe + 4H2O → Fe3O4 + H2

Step 4:  Balance other atoms now, like Fe and H.

Fe + 4H2O → Fe3O4 + H2

Atoms of H are 8 on L.H.S and 2 ON R.H.S, so multiply H2 on R.H.S with 4, so we get

Fe + 4H2O  →  Fe3O4 + 4H2

Step 5: Fe + 4H2O → Fe3O4 + 4H2

Pick the last element Fe from the above partly balanced equation. Fe are 3 on R.H.S and 1 on L.H.S, so multiply 3 on L.H.S

3Fe + 4H2O  →  Fe3O4 + 4H2

### Step 6:

Check whether the equation is balanced or not by counting the number of atoms on L.H.S and R.H.S

3Fe + 4H2O  →  Fe3O4 + 4H2

This is the balanced equation.

Step 7:  Indicate the physical state of all the reactants and products by writing symbols in brackets as subscripts in the right corner below the formula.

### Symbols:

The symbols are denoted with some letters. For solids, we use “s”; for liquids, we use “l”; for gases, we use “g”; for aqueous solutions, we use “aq.” These symbols help us to classify the type of equation.

### Balanced Equation Representation:

Take the example of the chemical equation

3Fe(s)  + 4H2O(l)   →  Fe3O4(s) + 4H2(g)

This chemical equation is called the Heterogeneous chemical equation. It is called the Heterogeneous equation, as reactants and products have different physical states.

Balanced equations need not contain physical states unless it is necessary. For example, catalyst and reaction conditions like temperature and pressure are represented above and below the arrow in the equation.

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