Chemical reaction and equation class 10

Types of chemical Reaction

Combination Reaction
Decomposition Reaction
Displacement Reaction
Double displacement Reaction
Oxidation and Reduction Reaction

[1] Combination Reaction:

Those reactions in which two or more substance combines to form a single substance are called combination reaction.

1. Magnesium and oxygen combine, when heated, to form magnesium oxide.

$2Mg(s)+O_{2}(g)\xrightarrow[]{combinatoin}2MgO(s)$

2. Hydrogens burn in oxygen to form water.

$2H_{2}(g)+O_{2}(g)\xrightarrow[]{combination}2H_{2}O$

Note:-Formation of water from hydrogen and oxygen is a combination reaction.

3. Calcium oxide(lime or quicklime) reacts vigorously with water to form calcium hydroxide(slaked lime)

$CaO(s)+H_{2}O(l)\xrightarrow[]{combination}Ca(OH)_{2}(s)$

Note:-Please note that it is solid calcium hydroxide, which is known as Salked lime. Salked lime is a white powder.

4. Carbon monoxide react with oxygen to form carbon dioxide.

$2CO(g)+O_{2}(g)\xrightarrow[]{combination}2CO_{2}(g)$

[2] Decomposition Reaction:

Those reaction in which a compound splits up into two or more simpler substances are known as decomposition reactions.

A decomposition reaction is just the opposite of a combination reaction

1. When calcium carbonate is heated, It decomposes to give calcium oxide and carbon dioxide gas.

$CaCO_{3}(s)\xrightarrow[Decomposition]{heat}CaO(s)+CO_{2}(s)$

Note:-When a decomposition reaction is carried out by heating, It is called thermal reaction.

2. When potassium chloride is heated in the presence of manganese dioxide catalyst, It decomposes to give potassium chloride and oxygen.

$2KClO_{3}(s)\xrightarrow[Decompose]{Heat}2Kcl(s)+3O_{2}(g)$

3. When ferrous sulphate is heated strongly, It decomposes to form ferric oxide, sulphur dioxide and sulphur trioxide.

$2FeSO_{4}(s)\xrightarrow[Decomposition]{Heat}Fe_{2}O_{3}(s)+SO_{2}(g)+SO_{3}(g))$

4.when lead nitrate is heated strongly, It breaks down to form simpler substances like lead monoxide, nitrogen dioxide and oxygen.

$2Pb(NO_{3})_{2}(s)\xrightarrow[decompostion]{Heat}2Pb(s)+4NO_{2}(g)+O_{2}(g)$

Note:-all the above decomposition reaction have been carried out by the action of heat.

5. When electric current is passed through acidified water, It decomposes to give by hydrogen gas and oxygen gas. This reaction can be represented as.

$2H_{2}O(l)\xrightarrow[Decomposition]{Heat}2H_{2}(g)+O_{2}(g)$

Note:-1. This decomposition reaction which are carried out by using electricity.

2. A decomposition reaction is just the opposite of a combination reaction.

8. When silver chloride is exposed to light, It decomposes to form silver metal and chlorine gas:

$2AgCl(s)\xrightarrow[Decomposition]{Heat}2Ag(s)+Cl_{2}(g)$

Decomposition of silver chloride is caused by light

Use of Decomposition Reaction:

The decomposition reaction carried out by electricity are used to extract several metals from their naturally occurring compounds like chlorides or oxides.
The digestion of food in the body is an example of decomposition reaction.
Manufacture of cement or calcium oxide.
Thermite welding

[3] Displacement Reaction:

Those reactions in which one element takes the place of another element in a compound are known as displacement reaction.

1. When a strip of zinc metal is placed in copper sulphate solution, then zinc sulphate solution and copper are obtained.

$CuSO_{4}(aq)+Zn(s)\rightarrow ZnSO_{4}(aq)+Cu(s)$

This displacement reaction takes place because zinc is more reactive than copper.

2. When a piece of magnesium metal is placed in copper sulphate solution, then magnesium sulphate solution and copper metal are formed.

$CuSO_{4}(aq)+Mg(s)\rightarrow MgSO_{4}(aq)+Cu(s)$

Magnesium is able to displace copper from copper sulphate solution because magnesium is more reactive than copper.

3. When a copper strip is placed in a solution of silver nitrate, then copper nitrate solution and silver metal are formed.

$2AgNO_{3}(aq)+Cu(s)\rightarrow Cu(NO_{3})_{2}(aq)+2Ag(s)$

This displacement reaction occurs because copper is more reactive than silver.

Note:-In single displacement reaction only one element displaced.

Reactive Series of Metals:

[4] Double Displacement Reaction:

Those reactions in which two compounds react by an exchange of ions to form two new compounds are called double displaced reaction.

1. When silver nitrate solution is added to sodium chloride solution, then a white precipitate of silver chloride is formed along with sodium nitrate solution.

$AgNO_{3}(aq)+NaCl(aq)\xrightarrow[]{double .displacement}AgCl(s)+NaNO_{3}(aq)$

2. When ammonium hydroxide solution is added to aluminium chloride solution, then a white precipitate of aluminium hydroxide is formed along with ammonium chloride solution.

$AlCl_{3}(aq)+3NH_{4}OH(aq)\xrightarrow[]{double .displacement}Al(OH)_{3}(s)+3NH_{4}Cl(aq)$

3. When potassium iodide solution is added to lead nitrate solution, then a yellow precipitate of lead iodide is produced along with potassium nitrate solution.

$Pb(NO_{3})_{2}(aq)+2KI(aq)\xrightarrow[]{double .displacement}PbI_{2}(s)+2KNO_{3}(aq)$

[5] Oxidation and Reduction Reaction:

The earlier concepts of oxidation and reduction is based on the addition or removal of oxygen or hydrogen element. So, in terms of oxygen, oxidation and reduction reactions can be defined as follows.

Oxidation:-(i) The addition of oxygen to a substance is called oxidation.

(ii) The removal of hydrogen from a substance is called oxidation.

Reduction:-(i) The addition of hydrogen to a substance is called reduction.

(ii) The removal of oxygen from a substance is called reduction.

Note:- The oxidation and reduction are also called redox reaction if performed in same reaction.

Q1:-When copper is heated with hydrogen,then cooper metal and water are formed.

$CuO+H_{2}\overset{Heat}{\rightarrow}Cu+H_{2}O$

Ans:-

Q2. When hydrogen sulphide reacts with chlorine, then sulphur and hydrogen chloride are formed.

Ans:-

Effects of Oxidation Reactions in Everyday Life:

There are two common effects of oxidation reactions which we observed in daily life. There are:

Corrosion of metals
Rancidity of food

Corrosion:-

Corrosion is the process in which metals are eaten up gradually by the action of air, moisture or a chemical(such as an acid) on their surface). Rusting of Iron is the most common form of corrosion.

$4Fe+3O_{2}+2xH_{2}O\rightarrow 2Fe_{2}O_{3}xH_{2}O$

The rusting of iron is a redox reaction. Corrosion weakens the iron and steel objects and structures such as railing, car bodies, bridges and ships, etc. and cuts short their life.

Rancidity:-

Oxidation also has a damaging effect on foods containing fats and oils. When the food materials prepared in fats and oils are kept for a long time, they start giving unpleasant smell and taste. The fat and oil containing food materials which give unpleasant smell and taste are said to have become rancid(sour or stale). Rancidity is called "vikritgandhita" in Hindi.

The development of rancidity of food can be prevented or restarted(slowed down) in the following ways.

1. Rancidity can be prevented by adding anti-oxidants to foods containing fats and oils.

The tow common ant-oxidants used in foods to prevents the development of rancidity are BHA(Butylated Hydroxy-Anisole) and BHT(Butylant Hydroxy-Toluence).

2. Rancidity can be prevented by packing fat and oil containing foods in nitrogen gas.

3.rancidity can be retarded by keeping food in a refrigerator.

4. Rancidity can be retarded by storing food in air- tight containers.

5. Rancidity can be retarded by storing foods away from light.

Mind Map of chemical reaction and equation:

S.Chand Chemical Reaction and Equation Solution Download.

Download

Online Quiz of Chemical Reaction and Equation

Quiz1
Quiz2

Chemical reaction and equation class 10 | cbse24