Chemistry Proje

ct

Decomposition And Double

Displacement Reaction

Efforts By -• Saksham Gupta• X A• Roll no. – 23• Student id – 27/2000

Chemical ReactionA chemical reaction is a process

that leads to the transformation of one set of chemical substances to another. Chemical reactions can be either spontaneous, requiring no input of energy, or non-spontaneous, typically following the input of some type of energy, viz. heat, light or electricity.

Types Of Chemical Reaction

There are basically 6 types of chemical reactionCombination ReactionDecomposition ReactionDisplacement ReactionDouble Displacement ReactionOxidation and ReductionPrecipitation Reaction

In this presentation we will focus on Decomposition and Double Displacement Reaction.

Decomposition Reaction

Chemical decomposition, analysis or breakdown is the separation of a chemical compound into elements or simpler compounds. The stability that a chemical compound ordinarily has is eventually limited when exposed to extreme environmental conditions like heat, radiation, humidity or the acidity of a solvent.

To visualize a decomposition reaction look at the following cartoon:

Examples

• 2H2O2 → 2H2O + O2

• H2CO3 → H2O + CO2

• CaCO3 → CaO + CO2

• 2KClO3 → 2KCl + 3O2

Types Of Decomposition Reactions

There are four types of decomposition reaction:Thermal DecompositionCatalytic DecompositionPhotolytic DecompositionElectrolytical Decomposition

Thermal Decomposition

Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The reaction is usually endothermic as heat is required to break chemical bonds in the compound undergoing decomposition.

EXAMPLESSome examples of Thermal Decomposition Reaction

are: 2KClO3 + heat → 2KCl + 3O2

Water, when heated to well over 2000 °C, decomposes to its constituent elements:

2 H2O+ heat → 2 H2 + O2

The compound with the highest known decomposition temperature is carbon monoxide at ≈3870 °C (≈7000 °F)

Catalytic DecompositionIn catalysis, the reaction does not proceed directly,

but through a third substance known as catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself; however, it can be inhibited, deactivated or destroyed by secondary processes. Many substances such as Platinum , Palladium , Iron are used as Catalyst for decomposition reactions

Examples•  A catalyst is added to speed things

along.   The KI added dissociates into K+ and I-, at which point the I- begins its work.  The reaction pathway represented below has a lower activation energy than the straight decomposition represented above:

•      H2O2(aq) + I-(aq) -> OI-(aq) + H2O(l)

•      H2O2(aq) + OI-(aq) -> H2O(l) + O2(g) + I-(aq)

Catalytic Converter

Catalytic converters change poisonous molecules like carbon monoxide and various nitrogen oxides in car exhausts into more harmless molecules like carbon dioxide and nitrogen. They use expensive metals like platinum, palladium and rhodium as the heterogeneous catalyst.

Photolytic decomposition

Chemical process by which molecules are broken down into smaller units through the absorption of light

This photochemical reaction is used in black and white photography--

2AgBr ---- Sunlight ---- > 2Ag + BR 2

photolytic decomposition of silver chloride: 2AgCl --------sunlight---> 2Ag +Cl 2

Electrolytic Decomposition

When electrical energy is needed to decompose a substance , the process is called electrolysis.

Generally DC is used for electrolysis of any substance and many substances are obtained by electrolytic decomposition such as Sodium, Hydrogen etc.

Examples

2 H2O(l) → 2 H2(g) + O2(g); E0 = +1.229 V

2NaCl+electricity --->2Na + Cl2

DOUBLE DISPLACEMENT

REACTION

Double Displacement Reaction

In a double replacement reaction parts of two compounds switch places to form two new compounds. Two reactants yield two products. For example when silver nitrate combines with sodium chloride, two new compounds--silver chloride and sodium nitrate are formed because the sodium and silver switched places. The chemical equation for this double replacement reaction looks like:

reactant + reactant ---------> product + productTo visualize a double replacement reaction look at the following cartoon:

examplesThis is a reaction in which the positive and

negative ions of two substances in a solution are mutually interchanged.