CBSE 10th Science Term-2 Exam 2022 : Most Important Chemical Reactions To Revise Before Exam

 


Chapter 1

Chemical Reactions and Equations

• Mg + O→ 2MgO

• Zn + H2SO4→ ZnSO4 + H2

• 3Fe + 4H2O → Fe3O4 + 4H2

• CaO (s)                                 +             H2O (l) →             Ca (OH)2 (aq)

(Quick lime)                                                                     (Slaked lime)

• C(s) + O2 (g) → CO2 (g)

• 2 H2 (g) + O2 (g) → 2H2O (l)

• CH4 (g) + 2 O2 (g) → CO2 (g) + 2H2O (g)

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

  (Glucose)                     (Oxygen)        

• 2FeSO4(s)                    →        Fe2O3 (s)          +          SO2 (g)            +          SO3 (g)

  (Ferrous sulphate)                  (Ferric oxide)

• CaCO3(s)         +          Heat                 →        CaO (s)            +          CO(g)

 (Limestone)                                                     (Quick lime)

• 2Pb (NO3)2 (s)              +          Heat    →        2PbO(s)           +          4NO(g)          +          O(g)

(Lead nitrate)                                                   (Lead oxide)               (Nitrogen dioxide)

• Na2SO4 (aq) + BaCl(aq) → BaSO4 (s) + 2NaCl (aq)

• ZnO + C →Zn + CO

• MnO+ HCl →MnCl 2 + 2H2O + Cl2

Chapter 2

Acids, Bases and Salts

 

• Reaction of acids and bases with metals:

Acid + Metal → Salt + Hydrogen gas

Example:

2 NaOH           +          Zn        →        Na2ZnO2          +          H2

                                                            (Sodium zincate)

• Reaction of base and acid to give salt (neutralisation reaction):

NaOH(aq) + HCl(aq) → NaCl(aq) + H2O(l)

Other reactions:

Chapter 3

Metals and Non-metals

• Chemical properties of metals:

Metal + Oxygen → Metal oxide

Example:

• 2Cu + O2 → 2CuO

• 4Al + 3O2 → 2Al2O3

Aluminum oxide reacts in the following manner with acids and bases:

• Al2O+ 6 HCl → 2 AlCl3 + 3 H2O

• Al2O3 + 2 NaOH → 2 NaAlO+ H2O

Sodium oxide and potassium oxide dissolve in water to produce alkalis:

• Na2O(s) + H2O (l) → 2 NaOH (aq)

• K2O(s) + H2O (l) → 2 KOH (aq)

Reactions of Metal with water

Metal + Water → Metal oxide + Hydrogen

Metal oxide + Water → Metal hydroxide

Example:

• 2K(s) + 2H2O (l) → 2KOH (aq) + H(g) + heat energy

• 2Na(s) + 2H2O (l) → 2 NaOH (aq) + H(g) + heat energy

• Ca(s) + 2 H2O (l) → Ca (OH)2 (aq) + H2(g)

• 2 Al (s) + 3H2O (g) → Al2O3 (s) + 3H2 (g)

• 3 Fe (s) + 4H2O (g) → Fe3O4(s) + 4H2 (g)

Check formation of NaCl and its electron dot structure form NCERT Textbook.

Chemical reactions related to extraction of metal are also important for CBSE 10th Science Board Exam 2019:

Chapter 4

Carbon and its Compounds

Chemical Properties of Carbon Compounds

Combustion of carbon and its compounds:

(i) C + O2 → CO2 + heat and light

(ii) CH4 + 2O2 → CO2 + 2H2O + heat and light

(iii) CH3CH2OH + 2O2 → 2CO2 + 3H2O + heat and light

Oxidation of carbon compounds:

Conversion of alcohol to carboxylic acid

 

Addition Reaction:

Hydrogenation of vegetable oils using a nickel catalyst:

Properties of Ethanol:

Reactions of Ethanol with sodium –

2Na + 2CH3CH2OH →                        2 CH3CH2O–Na+         +         H2

                                                (Sodium ethoxide)

Heating of ethanol:

Heating ethanol at 443 K with excess concentrated sulphuric acid results in the dehydration of ethanol to give ethene –

Esterification reaction:

Esters (sweet-smelling substances used in making perfumes and as flavouring agents) are most commonly formed by reaction of an acid and an alcohol. Ethanoic acid reacts with absolute ethanol in the presence of an acid catalyst to give an ester –

Saponification:

Esters react in the presence of an acid or a base to give back the alcohol and carboxylic acid. This reaction is known as saponification because it is used in the preparation of soap.

Chapter 6

Life Processes

 

Process of photosynthesis

 

Chapter 14

Sources of Energy

Nuclear fusion: Most commonly hydrogen or hydrogen isotopes to create helium, such as

2H + 2H → 3He (+ n)

It releases a tremendous amount of energy

Chapter 15

Our Environment

Formation of ozone:

Ozone at the higher levels of the atmosphere is a product of UV radiation acting on oxygen (O2) molecule. The higher energy UV radiations split apart some moleculer oxygen (O2) into free oxygen (O) atoms. These atoms then combine with the molecular oxygen to form ozone as shown

 

 

 

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