This presentation is based on the chapter 1 of chemistry .this presentation includes the basic informations related with the chemical Reactions and their characteristics. it will help students and teachers in the teaching learning process.

1. BY: VEENU GUPTA
BY : VEENU GUPTA (CHEM)6/5/2020

2. CHEMICAL REACTION
 The transformation of chemical substance into a new chemical
substance by making and breaking of bonds between different
atoms is known as Chemical Reaction.
 For example:
Rusting of iron, the setting of milk into curd, digestion of food,
respiration, etc.
 A chemical reaction involves a chemical change in which
substances react to form new substances with entirely new
properties.
 During a chemical reaction, there is a breaking of bonds between
atoms of the reacting molecules to give products.
BY : VEENU GUPTA (CHEM)6/5/2020

3. Example of chemical reaction
 The burning of magnesium in the air to form
magnesium oxide(white ash) is an example of a
chemical reaction.
2Mg(s) + O2(g) →2MgO(s)[Basic in nature]
 Before burning in air, the magnesium ribbon is
cleaned by rubbing with sandpaper. This is done to
remove the protective layer of basic Magnesium
carbonate from the surface of the magnesium ribbon.
 2Mg(s) + O2(g)+ CO2(g) →2MgCO3(s)
BY : VEENU GUPTA (CHEM)6/5/2020

4. Reactants & Products
Reaction: 2Mg(s) + O2(g) →2MgO(s)
 Substances which take part in a chemical reaction
are called reactants.
Example: Mg and O2.
 New substance formed after a chemical reaction is
called a product.
Example: MgO.
BY : VEENU GUPTA (CHEM)6/5/2020

5. Characteristics of Chemical Reactions
 EVOLUTION OF GAS
 CHANGE IN COLOUR OF SOLUTION
 FORMATION OF PRECIPITATES
 CHANGE IN STATE OF SUBSTANCE
 CHANGE IN TEMPERATURE
BY : VEENU GUPTA (CHEM)6/5/2020

6. (i) Evolution of gas
The chemical reaction between zinc and dilute
sulphuric acid is characterised by the evolution of
hydrogen gas.
Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) ↑
BY : VEENU GUPTA (CHEM)6/5/2020

7. REACTION BETWEEN ZINC GRANULES AND
DILUTE SULPHURIC ACID
BY : VEENU GUPTA (CHEM)6/5/2020

8. Test For Hydrogen Gas
 The gas evolved after reaction of acid with
metal can be tested by bringing a lighted
candle near it.
 If the gas bums with a pop sound, then it
confirms the evolution of hydrogen gas.
 Burning with pop sound is the characteristic
test for hydrogen gas.
BY : VEENU GUPTA (CHEM)6/5/2020

9. (ii) Change in Colour
 When Iron reacts with copper sulphate , it forms Iron
sulphate and copper metal and the colour of solution
changes from blue to green and there is no formation of
ppts.
Fe (s) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)
(Blue colour ) (green colouration)
 The chemical reaction between citric acid and purple
coloured potassium permanganate solution is characterised
by a change in colour from purple to colourless.
 The chemical reaction between sulphur dioxide gas and
acidified potassium dichromate solution is characterized by a
change in colour from orange to green.
BY : VEENU GUPTA (CHEM)6/5/2020

10. iii) Formation of precipitates
 When the solution of barium chloride reacts
with the solution of sodium sulphate, white
precipitates of barium sulphate are formed
along with sodium chloride.
BaCl2 (aq) + Na2SO4(aq) → BaSO4 (s) + 2 NaCl (aq)
(White ppt)
 When the solution of Lead Nitrate reacts with
the solution of Potassium Iodide, Yellow
precipitates of Lead Iodide are formed along
with Potassium Nitrate.
Pb(NO3)2 (aq) + 2 KI (aq) → PbI2 ( ↓ ) + 2 KNO3 (aq)
(yellow ppt)
BY : VEENU GUPTA (CHEM)6/5/2020

11.  When the solution of Silver Nitrate reacts with the solution of
sodium chloride then white ppts of silver chloride are formed
along with sodium Nitrate
 AgNO3 (aq) + NaCl (aq) → AgCl ( ↓ ) + NaNO3 (aq)
(white ppt)
 When the solution of Silver Nitrate reacts with the solution of
sodium bromide then Yellow precipitates of silver bromides are
formed along with sodium Nitrate
 AgNO3 (aq) + NaBr (aq) → AgBr ( ↓ ) + NaNO3 (aq)
(yellow ppt)
 The chemical reaction between sulphuric acid and barium
chloride solution is characterised by the formation of a white
precipitate of barium sulphate.
BaCl2(aq) + H2SO4(aq) → BaSO4(s) + 2HCl(aq)
(white ppt)
BY : VEENU GUPTA (CHEM)6/5/2020

12. (IV) Change in state of substance
 The combustion reaction of candle wax is characterised by a
change in state from solid to liquid and gas (because the wax
is a solid, water formed by the combustion of wax is a liquid
at room temperature whereas, carbon dioxide produced by
the combustion of wax is a gas).
 There are some chemical reactions which can show more
than one characteristics.
BY : VEENU GUPTA (CHEM)6/5/2020

13. [v] CHANGE IN
TEMPERATURE
BY : VEENU GUPTA (CHEM)6/5/2020

14. Reactions involving increase in
temperature:
 The chemical reaction between quick lime & water to form slaked
lime is characterized by rise in temperature .
Ca0 + H2O → Ca(OH)2
 The chemical reaction between zinc granules and dilute sulphuric
acid is also characterised by rise in temperature.
Zn + 2H2SO4 → ZnSO4 + H2
 The chemical reaction between zinc granules and dilute
Hydrochloric acid is also characterised by a rise in temperature.
Zn + 2HCl → ZnCl2 + H2
 Respiration is also a chemical reaction which involves increase in
temperature.
 Most of the combinations reactions occurs by an increase in
temperature of the solution.
BY : VEENU GUPTA (CHEM)6/5/2020

15. REACTIONS INVOLVING DECREASE IN
TEMPERATURE:
i) Thermal Decomposition of Lead Nitrate
2Pb(NO3)2 (s) + Heat → 2PbO(s) + 4NO2(g) + O2(g)
white brown gas
ii) Thermal Decomposition of Ferrous Sulphate
2 FeSO4 (s) + Heat → Fe2O3 (s) + SO2 (g) + SO3(g)
Ferrous Sulphate Ferric oxide Sulphur Sulphur
(green) (brown) dioxide trioxide
iii) Thermal Decomposition of calcium carbonate
CaCO3(s) + Heat → CaO(aq) + CO2 (g)
(Calcium Carbonate) ( calcium oxide)
BY : VEENU GUPTA (CHEM)6/5/2020

16. THANKS
BY : VEENU GUPTA (CHEM)6/5/2020