Chemical reactions and equations

BY UMANG SINGH GUSAIN

CHEMICAL REACTIONS AND

EQUATIONS

CONTENTS

• REACTANT / REAGENT• PRODUCTS• EXOTHERMIC REACTION • ENDOTHERMIC REACTION• SYMBOLS• BALANCED AND UNBALANCED CHEMICAL EQUATIONS• TYPES OF CHEMICAL REACTION• CORROSION• RANCIDITY

REACTANT

• REACTANTS (SUBSTRATES) ARE TWO OR MORE ELEMENTS/COMPOUNDS THAT CHEMICALLY INTERACT TO FORM A NEW SUBSTANCE. THEY ARE THE STARTING MATERIALS FOR A REACTION AND ARE ALWAYS FOUND AT THE END OF THE REACTION.

PRODUCTS

• PRODUCTS ARE FORMED DURING CHEMICAL REACTIONS. PRODUCTS HAVE LOWER ENERGY THAN THE REAGENTS AND PRODUCED DURING THE REACTION. PRODUCTS ARE FORMED AS THE CHEMICAL REACTION PROGRESSES TOWARDS CHEMICAL EQUILIBRIUM AT A CERTAIN REACTION RATE, WHICH DEPENDS ON THE REAGENTS AND ENVIRONMENTAL CONDITIONS.

EXOTHERMIC REACTION

• AN EXOTHERMIC REACTION IS A CHEMICAL REACTION THAT IS ACCOMPANIED BY THE RELEASE OF HEAT.

• THE ENERGY NEEDED FOR THE REACTION TO OCCUR IS LESS THAN THE TOTAL ENERGY RELEASED.

• AS A RESULT OF THIS, THE EXTRA ENERGY IS RELEASED, USUALLY IN THE FORM OF HEAT.

EXAMPLES• BREATHING• WHITE WASHING• COMBUSTION REACTIONS OF

FUELS• NEUTRALIZATION REACTIONS SUCH

AS DIRECT REACTION OF ACID AND BASE

• ADDING CONCENTRATED ACID TO WATER

• BURNING OF A SUBSTANCE• ADDING WATER TO ANHYDROUS

COPPER(II) SULPHATE

• REACTIONS TAKING PLACE IN A SELF-HEATING CAN BASED ON LIME AND ALUMINIUM

• THE SETTING OF CEMENT AND CONCRETE

• MANY CORROSION REACTIONS SUCH AS OXIDATION OF METALS

• MOST POLYMERISATION REACTIONS

• THE HABER-BOSCH PROCESS OF AMMONIA PRODUCTION

ENDOTHERMIC REACTION

• An endothermic reaction is a chemical reaction in which energy is absorbed from the surrounding environment in place of being released as it is in the exothermic reaction. It is also called as a hypothermic reaction. Heat is compulsory for this reaction as it is absorbed during the reaction takes place.

EXAMPLES

• MELTING ICE CUBES• MELTING SOLID SALTS• EVAPORATING LIQUID

WATER• CONVERTING FROST TO

WATER VAPOUR (MELTING, BOILING, AND EVAPORATION)

• MAKING AN ANHYDROUS SALT FROM A HYDRATE

• SPLITTING A GAS MOLECULE

• REACTING ETHANOIC ACID WITH SODIUM CARBONATE

• PHOTOSYNTHESIS (CHLOROPHYLL IS USED TO REACT CARBON DIOXIDE PLUS WATER PLUS ENERGY TO MAKE GLUCOSE AND OXYGEN)

TYPES OF CHEMICAL REACTIONS

• COMBINATION REACTION• DECOMPOSITION REACTION• DISPLACEMENT REACTION• DOUBLE DISPLACEMENT REACTION• REDOX REACTION

COMBINATION REACTION

• A COMBINATION REACTION IN WHICH TWO OR MORE REACTANTS ARE CHEMICALLY BONDED TOGETHER TO PRODUCE A SINGLE PRODUCT.

• WHEN TWO OR MORE SUBSTANCES COMBINE TO FORM A SINGLE PRODUCT, IT IS KNOWN AS A COMBINATION REACTION.

• THIS REACTION IS USUALLY EXOTHERMIC BECAUSE WHEN THE BOND FORMS BETWEEN THE ELEMENTS, HEAT IS RELEASED.

TYPE EXAMPLE

A) BETWEEN TWO ELEMENTS

C + O2 → CO2

B) BETWEEN TWO COMPOUNDS

CaO + H2O → Ca(OH)2

C) BETWEEN AN ELEMENT AND A COMPOUND

O + H2O → H2O2

DECOMPOSITION REACTION

• A DECOMPOSITION REACTION IS A TYPE OF CHEMICAL REACTION IN WHICH A SUBSTANCE DEGRADES INTO TWO OR MORE BASIC COMPONENTS

• THE DECOMPOSITION REACTION OFTEN REQUIRES EXPOSURE TO A CATALYST, SUCH AS A HEAT SOURCE OR SOLVENT

• Eg : CONVERSION OF WATER (H2O) INTO HYDROGEN (H2) AND OXYGEN (O2) GAS VIA A PROCESS KNOWN AS THE ELECTROLYSIS OF WATER.

TYPES OF DECOMPOSITION REACTION

• CATALYTIC• ELECTROLYTIC• THERMAL

DISPLACEMENT REACTION

• DISPLACEMENT REACTIONS ARE THE REACTIONS IN WHICH A MORE REACTIVE ELEMENT DISPLACES A LESSER REACTIVE ELEMENT FROM IT’S COMPOUND IS KNOWN AS DISPLACEMENT REACTION

• THESE REACTIONS ARE GENERALLY FOUND TO OCCUR IN SOLUTIONS. THE ELEMENTS INVOLVED MAY BE METALS, NON-METALS, I.E., A MORE REACTIVE METAL MAY DISPLACE A LESSER REACTIVE METAL OR A MORE REACTIVE NON-METAL MAY DISPLACE A LESSER REACTIVE NON-METAL.

EXAMPLE

1. Mg + 2 H2O ---> Mg(OH)2 + H2

2. 2 KI + Cl2 ---> 2 KCl + I2

DOUBLE DISPLACEMENT REACTIONS

• THE REACTION IN WHICH TWO COMPOUNDS REACT BY AN EXCHANGE OF IONS TO FORM TWO NEW COMPOUNDS. A DOUBLE DISPLACEMENT REACTION USUALLY OCCURS IN SOLUTION AND ONE OF THE PRODUCTS, BEING INSOLUBLE PRECIPITATES OUT.

• AB+CD AD + BC

EXAMPLE

AgNO3+NaCl----->AgCl+NaNO3

REDOX REACTION

AN OXIDATION-REDUCTION REACTION (REDOX REACTION) IS A REACTION IN WHICH ELECTRONS ARE TRANSFERRED BETWEEN SPECIES OR IN WHICH ATOMS

CHANGE OXIDATION NUMBERS. OXIDATION IS THE PORTION OF THE REDOX REACTION IN WHICH

THERE IS A LOSS OF ELECTRONS BY A SPECIES OR AN INCREASE IN THE OXIDATION NUMBER OF AN ATOM.

REDUCTION IS THE PART OF A REACTION IN WHICH THERE IS A GAIN OF ELECTRONS BY A SPECIES OR A DECREASE IN THE OXIDATION NUMBER OF AN ATOM.

SOMETHING THAT IS OXIDIZED LOSES ELECTRONS OR CONTAINS AN ATOM THAT INCREASES IN OXIDATION NUMBER.

SOMETHING THAT IS REDUCED GAINS ELECTRONS OR HAS AN ATOM THAT DECREASES IN OXIDATION NUMBER.

CORROSION

• CORROSION IS THE DISINTEGRATION OF AN ENGINEERED MATERIAL INTO ITS CONSTITUENT ATOMS DUE TO CHEMICAL REACTIONS WITH ITS SURROUNDINGS.

• THIS MEANS ELECTROCHEMICAL OXIDATION OF METALS IN REACTION WITH AN OXIDANT SUCH AS OXYGEN.

• IN OTHER WORDS, CORROSION IS THE WEARING AWAY OF METALS DUE TO A CHEMICAL REACTION.

CORROSION PREVENTION

• BARRIER PROTECTION• SACRIFICIAL PROTECTION• CATHODIC PROTECTION• ANTI RUST SOLUTIONS

RANCIDITY

• RANCIDITY IS A VERY GENERAL TERM AND IN ITS MOST GENERAL MEANING, IT REFERS TO THE SPOILAGE OF A FOOD IN SUCH A WAY THAT IT BECOMES UNDESIRABLE (AND USUALLY UNSAFE) FOR CONSUMPTION.

RANCIDITY PREVENTION

• VACCUM PACKING• REFERIGERATION• REPLACEMENT OF AIR WITH INERT GASES LIKE

NITROGEN DIOXIDE• ANTIOXIDANT SUBSTANCES

• THANK YOU