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Title: Chemical reactions and equations notes
Description: class 10th science chapter 1
Description: class 10th science chapter 1
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Revision Notes for Class 10 Science
Chapter 1 – Chemical Reactions and Equations
Chemical Change: A change that results in the formation of one or more new compounds
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Observations in a Chemical Reaction
In a chemical reaction or chemical change, the following observations can be made,
•
Formation of new substances
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•
Changes in energy
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•
Change in temperature
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•
Formation of a precipitate
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Cooking of food
B
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Heating of Lead nitrate
D
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Ripening of fruit
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vedantu
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a
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It demonstrates that one molecule of water is
made up of two hydrogen atoms and one oxygen atom
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One molecule of sulphuric acid has the formula H2SO4
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Chemical Equations - The chemical equation of the reaction is the representation of a
chemical change in terms of symbols and formulae of the reactants and products
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Step I: Writing Skeletal Equation
A word-equation depicts the transformation of reactants into products by placing an arrow
between them ( → )
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"
The reactants are on the left (LHS) of the arrow, while the products are on the right (RHS)
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A balanced account of a chemical transaction is a complete chemical equation, which
symbolically depicts the reactants, products, and their physical states
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Step II: Balancing of Chemical Equation
A balanced chemical equation is one in which the number of atoms of each element is equal
on both sides of the equation
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Equations must be balanced at all times
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If there are 4 H2O hydrogen atoms, then
4 2 = 8 hydrogen atoms are present
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There must be an even number in front of HCl on the reactant side
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) As a result, there will be an even amount of chlorine atoms (i
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, KCl=1
, MnCl2 = 2 , Cl2 = 2
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e
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However, the quantity of chlorine atoms in the
product is unusual
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Let's alter it to the
simplest even number we can think of, which is 2
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2KMnO4 + HCl → 2KCl + MnCl2 + H2O + Cl2
In 2 KMnO4 , there are 2 K, 2 Mn, and 8 O
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2KMnO4 + HCl → 2KCl + 2MnCl2 + 8H2O + Cl2
If there are 8 H2O on the product side, there should be 16 H (8 x 2) on the reactants side as
well
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vedantu
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On the left hand side, there are 16 Cl
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So, 10
more Cl atoms are to be accounted for
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2KMnO4 + 16HCl → 2KCl + 2MnCl2 + 8H2O + 5Cl2
The Hit and Trial approach is a technique for balancing chemical equations
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Let the number of molecules on each side be,
aKMnO4+ bHCl → cKCl + dMnCl2 + eH2O + fCl2
Now comparing LHS and RHS,
K: a = c
Mn: a = d
O: 4a = e
H: b = 2e
Cl: b = c + 2d + 2f
Let us take a = 2, then
c=d=a=2
b = 2e = 8a = 16
So, e = 8
So, 16 = 2 + 2(2) + 2(f)
Class X Science
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4
f=5
Thus, the required equation is: 2KMnO4+ 16HCl → 2KCl + 2MnCl2 + 8H2O + 5Cl2
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Various reactants and products names
B
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The number of moles of the reactants and products in relation to each other
D
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Volumes of gaseous reactants and products in relation to each other
In short – the Steps Involved in Balancing a Chemical Equation can be Listed As:
Step 1: Write the skeleton equation correctly
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Step 3: Start by balancing elements that only appear once on each side of the arrow
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Step 4: The Elementary substances are balanced last
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5
Types of Reactions
A
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Types of Combination reactions:
1
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2H 2(g)
→ O2(g) + 2H 2 O( l )
Hydrogen
Oxygen
Water
2
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2CO(g) + O2(g) → 2CO2(g)
3
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NH3(g) +
Ammonia
Colourless
HCl(g)
→
Hydrogen chloride
Colourless
NH 4Cl(s)
Ammonium chloride
White
B
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A decomposition reaction occurs when a complex is broken down into two or more simple
components using heat or electricity
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vedantu
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Electrolysis is the process of decomposing a substance by putting an electric current through
it
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1
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Thermal decomposition
2HgO(s) ⎯⎯⎯⎯⎯⎯⎯
→
Mercuric oxide
Red
2Hg (l) +
Mercury
Silvery liquid
O 2(g)
Oxygen
2
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Thermal decomposition
2Cu(NO3 )2(s) ⎯⎯⎯⎯⎯⎯⎯
→
2CuO(s) +
4NO2(g) + O2(g)
Copper nitrate
Copper
Nitrogen
Blue
oxide
dioxide
Black
Oxygen
Reddishbrown
3
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Electrolytic Decomposition
2H 2O(l) ⎯⎯⎯⎯⎯⎯⎯⎯
→
Water
2H 2(g) + O2(g)
Hydrogen
Oxygen
4
...
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7
Electrolytic decomposition
PbBr2 ⎯⎯⎯⎯⎯⎯⎯
⎯
→
Lead bromide
(molten)
Pb(s) +
Lead
Br2(l)
Bromine
Activity Seri
Title: Chemical reactions and equations notes
Description: class 10th science chapter 1
Description: class 10th science chapter 1