Question

Define chemical reaction. With hat are the types of chemical reaction? ​

Answer 1

Chemical reaction is a process of forming new product by the reaction of two or more than two reactants. Chemical reactions occurs when two reactants of similar or different properties react together. A new substance is formed when the different chemicals are reacted together.

Examples of chemical reaction:

• Na + Cl  ----> Nacl

• NaOH + H2SO4 -----> Na2SO4 + H20

In a chemical reaction, The two reactants react with each other to form new product. The new product formed may have same physical properties, but the chemical properties always changes. While chemical reaction, no atoms are destroyed nor new atoms are formed. Only, The atoms are rearranged to form new substance.

Chemical reactions are of 4 types: Composition, Decomposition, Single replacement , Double replacement.

Composition

• A + B  →  AB  (One product from two reactants)

Decomposition reaction

• AB  →  A + B  (Two products from one reactant)

Single Displacement reaction

• A + BC    →  AB + C  (One of the element is replaced)

Double displacement reaction

• AB + CD    →  AD + BC (Both of the elements are replaced)

Examples of Chemical reaction:

• CH4 + 2O2 → CO2 + 2H2O

• C4H6O6 + NaHCO3 → NaC4H5O6+ H2O + CO2

• Na + Cl → NaCl

• 2 H2O → 2 H2 + O2

• HBr + NaOH → NaBr + H2O

What does a formula tell about substance:

• Formula of a substance tells us which substance are present in the reaction.

• We know about the proportion of a specific chemical used in it.
• Formula of substance tells it's nature, state, position, temperature and it's physical and chemical properties.

• Its chemical formula helps us to get know about the no. of atoms and molecules in it.

Example:

• Let's consider the example of Hydrochloric acid. We know the formula of Hydrochloric acid - H2SO4

• In this formula, there are elements called Sulphur, oxygen and hydrogen. Also, because of formula, we are able to understand it's all components and compounds in it.

• We can also know about it's Molar mass and molecular mass. We can also know about the proportion of the substance in it.

Answer 2

$\sf\underline\orange{Chemical \ Reaction}$

The process which leads to a chemical change of one substance to another is called Chemical Reaction.

Substances which undergo a chemical change in a reaction are called reactants.

The new substances formed after a chemical reaction are called products.

$\rm\boxed{Reactants \: \rightarrow \: Products}$

$\sf{2H_2+O_2 \rightarrow 2H_2O}$

In this $\sf{2H_2+O_2}$ are reactants and $\sf{2H_2O}$ is product.

The representation of a chemical reaction, using symbols and formulae of substances, involved in the reaction, is called a chemical equation.

$\sf\underline\orange{Types\:of\:Chemical\:Reactions}$

$\rm\red{Combination\:Reaction}$: A chemical reaction, in which two or more substance (reactants) combine to form a new substance (product), is called a combination reaction.

EXAMPLE :

• Combination of nitrogen and hydrogen gas yields ammonia gas.

$\sf{N_2+3H_2 \rightarrow 2NH_3}$

$\rm\red{Decomposotion\:Reaction}$: A chemical reaction, in which more than one product is obtained from a single reactant, is called a decomposition reaction.

EXAMPLE :

• Breaking up of water, into hydrogen and oxygen gases, on passing an electric current, is an example of a decomposition reaction.

$\sf2H_2+O_2 \rightarrow2H_2+O_2$

When we pass electricity through water then water molecules break into hey gas and oxygen gas.

This process is called Electrolysis of Water.

$\rm\red{Displacement\:Reaction }$: A chemical reaction in which one element displaces another in a compound is called, displacement reaction.

EXAMPLE :

• The chemical equation for this reaction is given below:

$\sf{Fe+CuSO_4 \rightarrow FeSO_4Cu}$

$\rm\red{Neutralisation\:Reaction }$: A chemical reaction, between an acid and a base, is called a neutralisation reaction. A neutralisation reaction always leads to the formation of salt and water.

EXAMPLE :

• The reaction between hydrochloric acid and sodium hydroxide (a base) yields sodium chloride (a salt) and water.

$\sf{Na(OH)_2+HCl \rightarrow NaCl+H_2O}$

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$\bf{Additional\:Information }$

What does a chemical equation represent?

A chemical equation represents —

1. Number of reactants participating in that reaction.
2. Number of product formed after the reaction.
3. Number of molecules of each compound.

What does a chemistry formula represents?

1. A chemical formula tells us the specific element present in the compound.
2. The number of atoms of each element present in the compound.
3. Symbols of each elements present in the compound.

Equation having same number of atoms of each element on both sides is called Balanced Equation.

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