Chemical Reaction, Types of Chemical Reaction and Factors Affecting its Rate: Simple Notes

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Activity: Observation of a Chemical Reaction

Objective: To observe a chemical reaction

Materials Required: a test tube, dropper, dilute hydrochloric acid, sodium hydroxide

Procedure

Take a test tube in the laboratory.
Put about 10 drops of dilute hydrochloric acid in the test tube with the help of a dropper according to the guidelines of your teacher.
Add about 10 drops of dilute sodium hydroxide in the test tube containing dilute hydrochloric acid.
Now, observe the change inside the test tube and draw a conclusion.

Chemical Equation

During a chemical change, there is loss and gain or sharing of electrons between the reactants where they either combine or decompose or exchange their ions to form products. Such a change process is known as a chemical reaction. The chemical reaction in which the reactants and products are written in the form of words, symbols, or chemical formulas is known as a chemical equation.

Activity:

Study the balanced chemical equation given below. On this basis, discuss the questions given below and draw a conclusion. Present your conclusion in the class.

2Al +3H2SO4———–> Al2 (SO4)3 +3H2

a. Name the reactants and Products.

b. How many atoms of each element are there in the reactants and products?

Types of Chemical Reactions

Combination Reaction

The chemical equation of the combination equation is of the following type.

A+B———> C

A chemical reaction in which two or more reactants combine to form only one product is called a combination reaction.

Some examples of chemical reactions are:

a. 2Na + Cl2 ————> 2 Nacl

(Sodium) (Chlorine) (sodium chloride)

b. C + O2 ———————-> CO2

(Carbon) (Oxygen) (Carbon dioxide)

c. N2 + 3H2 —————-> 2NH3

(Nitrogen) (Hydrogen) (Ammonia)

d. 2Mg + O2 ———————–> 2MgO

(Magnesium) (Oxygen) (Magnesium Oxide)

e. 4 Fe + 3 O2 ——————–> 2Fe2O3

(Iron) (Oxygen) (Ferric Oxide)

Decomposition Reaction

The chemical reaction of the decomposition reaction is of the following type.

AB—————–> A + B

The chemical reaction in which a reactant breaks down into two or more products is called a decomposition reaction. A reactant decomposes due to the effect of heat, pressure, or any other causes. For example, let us observe some chemical reactions.

CacO3 (s) ——-> CaO (s) + CO2 (g)

2NaOH (s)———-> Na2O (s) + H2O (l)

H2CO3 (aq) ———-> CO2 (g) + H2O (l)

2KCLO3 (s)————–> 2KCL (s) + 3O2 (g)

Activity:

ZnCO3———————–heat-—————> ZnO + CO2

Study the given reaction and discuss the questions asked.

a. What are the reactants and products in the chemical reaction given above?

Reactant – ZnCO3 (Zinc Carbonate)

Products – ZnO (Zinc Oxide) and CO2 (Carbon Dioxide)

b. What type of chemical reaction is it?

It is a decomposition reaction.

c. Write the balanced chemical equation of this reaction.

ZnCO3 ———————-heat—————> ZnO + CO2

Displacement Reaction

The chemical reaction in which an atom or radical of one reactant is displaced by the atom or radical of another reactant is called a displacement reaction. There are two types of displacement reactions.

i) Single Displacement Reaction

In this displacement reaction, one element or radical displaces an element or radical of another compound.

AB + C ——————> A + BC

Compound Element Element Compound

Zn (s) + H2SO4 (aq) ————————-> ZnSO4 (aq) + H2 (g)

Zn (s) + 2HCl (aq)——————————> ZnCl2 (aq) + H2(g)

Cu + 2AgNO3 ————–> 2Ag + Cu (NO3)2

Activity:

Objective: Copper plating an iron nail

Materials Required: beaker, copper sulphate solution, iron nail, thread

Procedure:

Take a beaker and half-fill it with copper sulphate solution.
Dip the iron nail into the solution and leave it overnight.
Observe the changes and discuss the following questions.

What change do you observe?
What are the reactants and products in this process?
What type of chemical reaction is this?
Write the balanced chemical reaction equation of this process.

ii. Double Displacement Reaction

The chemical reaction in which two new compounds are formed by the mutual exchange of atoms or radicals between two reactants is called a double displacement reaction.

AB + CD —————————————————-> AD + CB

NaCl + AgNO3 —————————–> AgCl + NaNO

BaCl2 + Na2So4 ——————-> BaSO4 + 2NaCl

Acid-Base Reaction

The reaction in which acid and base react to form salt and water is called an acid-base reaction. It is also a type of double displacement reaction. In the acid-base reaction, both the properties of acid and base are lost by each other and form neutral compounds. So, it is also known as a neutralization reaction.

Acid + Base ———————–> Salt + Water

HCl (acid) + NaOH (base) —————————-> NaCl (base) + H2O (water)

H2SO4 (acid) + 2NaOH (base)————————> Na2SO4 (base) + H2O (water)

Rate of Chemical Reaction

The change of reactants to products per unit of time in any chemical reaction is known as the rate of that chemical reaction.

At the initial stage of reaction, the concentration of reactants is maximum and the concentration of product is zero as no product is formed at that time. When the reaction starts then the concentration of the reactants goes on decreasing and the concentration of the product goes on increasing. Thus the concentration of both the reactants and products changes with time during the course of a chemical reaction.

Factors Affecting the Rate of Chemical Reaction

1. Catalyst

The substance which increases or decreases the rate of a chemical reaction is called a catalyst. These substances change the rate of chemical reaction but they remain chemically unchanged.

The catalyst which increases the rate of a chemical reaction is called a positive catalyst, and the catalyst which decreases the rate of a chemical reaction is called a negative catalyst.

Examples of Positive Catalyst – Manganese dioxide (MnO2), Vanadium Pentoxide (V2O5)

Examples of Negative Catalysts – Phosphoric Acid (H3PO4)

2. Heat

Heat is also one of the factors that affect the rate of chemical reactions. On increasing heat, temperature increases. The rate of chemical reaction increases with the increase in temperature. So, heat is directly proportional to the rate of a chemical reaction.

2. Pressure

The rate of reaction of gases depends on the pressure of the gases during a chemical reaction. Generally, the rate of reaction increases with the increase in pressure of the gases. So the reaction takes place with greater speed when the pressure is more.

4. Surface Area

If the surface area of contact of reactants is less, then the reaction takes place faster. Similarly, if the surface area of contact of the reactant is more, then the rate of reaction is also more.

5. Light

Some chemical reactions need light. The presence of light increases the rate of reaction.

6CO2 + 6H2O ———–light—————>C6H12O6 +6O2

carbon dioxide water glucose oxygen

In conclusion, the chemical reaction observed in the activity involving dilute hydrochloric acid and sodium hydroxide resulted in the formation of Al2(SO4)3 and H2. The activity also explored different types of chemical reactions, such as combination, decomposition, and displacement reactions. Additionally, the activity on copper plating an iron nail demonstrated a double displacement reaction. Factors affecting the rate of chemical reactions, such as catalysts, heat, pressure, surface area, and light, were also discussed. These factors play significant roles in determining the speed of chemical reactions.