Exothermic Reactions

Presented By-Soumya Vishwakarma

Contents:

Exothermic Reactions-What are they?

What Happens When an Exothermic Reaction Occurs?

Examples of Exothermic Reactions

Daily Life Examples of Exothermic Reactions

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Amount of Heat Released in Exothermic Reactions

Interesting Exothermic Reactions

An exothermic reaction is a chemical reaction that releases energy in the form of light or heat.

An exothermic reaction is a chemical or physical reaction that gives out energy to its surroundings.

It is the opposite of an endothermic reaction.

The energy needed for the reaction to occur is less than the total energy released.

Exothermic Reactions-What are They?

A reaction is EXOTHERMIC if a lot of energy is RELEASED.

What Happens When an Exothermic Reaction Occurs?

Step 1: Energy must be SUPPLIED to break chemical bonds

Step 2: Energy is RELEASED when new chemical bonds are made

Interesting Exothermic Reactions

Respiration is considered as an exothermic reaction because in respiration oxidation of glucose takes place which produces large amount of heat energy.Evaporation is both endothermic and exothermic reaction as heat is provided as well as evolved in the form of vapours.

Examples of Exothermic Reactions

• C(s)+ O2(g) →CO2(g) [Burning of Coal]• 3H2 + N2 →2NH3 + Heat [Formation of

Ammonia]

• 2H2(g) + O2(g)→H2O(l) [Formation of Water]

• 2SO2 + O2→ 2SO3 + Heat [Formation of Sulphur Trioxide]

• CH4(g) + 2O2(g)→CO2(g)+2H2O(g) [Burning of Natural Gas]

• CaO(s) + H2O(l)→Ca(OH)2(aq) [Formation of Slaked Lime]

• C6H12O6(aq) + 6O2(aq) → 6CO2(aq) + 6H2O(l) + energy [Respiration]

Amount of Heat Released in an Exothermic Reaction

In exothermic reactions energy is released and therefore ΔH  is negative. Heat is released by the system due to the reactants of the reaction having a greater enthalpy than the products. For example:-(1) Combustion of methane: CH4(g) + 2O2(g) ==> CO2(g) + 2H2O(l)        {ΔH=-883kJ/mol} This can also be written as   CH4(g) + 2O2(g) ==> CO2(g)+ 2H2O(l) + 883kJ/mol  This equation tells us that the combustion of methane is exothermic and releases 883 kilojoules of energy (in the form of heat) for every mole of methane (CH4). Given this information we can determine how much heat will evolve if we burn a certain mass of methane.(2) 2H2(g) + O2(g) → 2H2O(l) , then ∆H = -285 kJ/mol.

(3) Burning graphite (the most stable form of carbon) and then decomposing CO2 to CO and O2: C(s) + O2(g) → CO2(g) {∆rH2}

Daily Life Examples Of Exothermic Reactions

1. Combustion Combustion of Methane - CH4 +2O2 = CO2 + 2H2O

2. Photosynthesis 6CO2 + 12H2O C6H12O6 + 6O2 +6H2O3. Formation of SaltMixture of sodium metal and chlorine gas which yields table salt. 2Na(s) + Cl2(g) 2NaCl(s) + energy

Since in Exothermic Reactions Heat Energy EXITS the system ,Therefore some examples from daily life are :

Made By-Soumya Vishwakarma

Chemistry Creative- FA1