Chemistry Chapter-1 Chemical reaction and equation class 10 pdf notes and essential questions answer
CBSE has made it clear in their latest released syllabus that experiment learning should be used to learn concepts.
Chemical Reaction and Equation Class 10 chapter includes the topic:-chemical equation, balanced chemical equation, the implication of a balanced equation, types of chemical reaction- combination, decomposition, displacement, double displacement, precipitation, endothermic, exothermic reaction, oxidation, and reduction
Topic Notes
- Chemical reaction
- Chemical Equation
- Types of chemical reaction
- Effect of Oxidation Reaction in Daily Life
Previous Year Questions of chemical Reaction and Equation Class 10
Q.In which of the following, a chemical reaction has take place?
a) Ice melt in to water
b) A wet shirt got dried in sunlight
c) A brown layer is formed on iron rod kept in air
Show Answer
Ans-A brown layer is formed on iron rod kept in air
Show Answer
Ans-formation of crystal
Q. Which of the following condition help to us to determine that a chemical reaction has taken place?
a) Evolution of gas
b) Formation of precipitate
c) Change in colour
Show Answer
Ans- all of these
Q. Magnesium ribbon is rubbed before burning because it has a coating of –
a) Magnesium oxide
b) Magnesium carbonate
C) Magnesium sulphate
Show Answer
Ans- magnesium oxide
Q.If magnesium is gently heated, it forms-
a) Magnesium oxide
b)Magnesium carbonate
c) Magnesium sulphate
Show Answer
Ans- magnesium oxide
Q.Reaction of magnesium with air is –
a) Exothermic
b) Endothermic
c) Reversible
Show Answer
Ans- exothermic
Q. Which of the following is physical change?
a) Formation of curd from milk
b) Getting salt from sea water
c) Ripening of fruits
Show Answer
Ans- getting salt from sea water
Q. Which of the following is not a physical change?
a) Boiling of Water
b) Melting of ice
c) Combustion of LPG
Ans- combustion of LPG
Show Answer
Ans- combustion of LPG
Q. When magnesium ribbon is burnt in air, the ash formed is ——– in colour?
a) White
b) Yellow
c) Grey
d) Black
Show Answer
Ans- white
Q. Which of the following process involve chemical reaction?
a) Storing of oxygen gas in cylinder
b) Liquefaction of air
c) Heating of copper wire
Show Answer
Ans- heating of copper wire
Chemical Reaction and equation class 10 Test-paper-1
Q.A process employed for the concentration of sulphide ore is______
Froth floatation
Q.The slag obtained during the extraction of copper pyrites is composed mainly of_____.
FeSiO3
Q. In an electrolytic cell where electrolysis is carried, anode has:_____Charge?
Positive change
Q.In the reaction PbO + C → Pb + CO, carbon act as ____agent.
C act as a reducing agent
Q.A substance which oxidizes itself and reduces other is known as____.
Reducing agent
Q.What happens chemically when quick lime is added to water?
When quick lime is added to water calcium hydroxide (slaked lime) is formed with a hissing sound and lot of heat is evolved during the reaction. The reaction involved is
CaO (s) + H2O → Ca(OH)2 (s) + Heat
Q.Why a combustion reaction an oxidation reaction?
Because Combustion reaction is always carried out in the presence of air or
oxygen for e.g.: CH4 (g) + 2O2 (g) → CO2 (g) +2H2O (l)
Q.Why are food particle preferably packed in aluminum foil?
Aluminium foil do not corrode in atmosphere even if kept for a long time because a protective coating of aluminium oxide (Al2O3) is formed on the surface of the foil and stops any further reaction of the metal with air and water thus food particles do not get spoiled.
Q.What happens to lime water when CO2 gas is bubbled through it in excess?
When CO2 gas is bubbled through lime water in excess then initially it becomes milky but then its milkiness disappears.
Q.A student dropped few pieces of marble in dilute hydrochloric acid contained in a test tube. The evolved gas was then passed through lime water. What change would be observed in lime water? Write balanced chemical equation for both the change observed?
When marble reacts with dil. HCl, CO2 gas evolved
CaCO3 (s) +2HCl (aq) → CaCl2 (aq) + H2O (l) + CO2 (g)
When this gas is evolved and is passed through lime water, becomes milky due to the formation of insoluble Calcium carbonate
Ca (OH)2 + CO2 (g) → CaCO3 (s) +H2O (l)
But when milkiness disappears i.e. when CO2 gas is passed in excess through CaCO3 (s)
CaCO3 (s) + CO2 (g) +H2O (l) → Ca (HCO3)2 (aq)
Q.Give one example each of-
(1) Thermal decomposition
(2) Electrolytic decomposition
(3) Photo decomposition
(a) HCL has been oxidized to Cl2
(b) MnO2
(c) HCL is the reducing agent and MnO2 has been reduced to MnCl2
Chemical Reaction and equation class 10 Test-paper-2
Q.Some crystals of copper sulphate were dissolved in water. The colour of the solution obtained would be__?
blue
Q.When dilute HCl is added to zinc pieces taken in a test tube, then__
small bubbles of H2 gas appear on the surface of zinc pieces
Q.PbS reacts with ozone (O3) and forms PbSO4 . As per the balanced equation, molecules of ozone required for every one molecule of PbS is / are
4 molecule of ozone
PbS (s) + 4 O3 (g) → PbSO4 (s) + 4 O2 (g)
Q.Chemically rust is__________?
hydrated ferric oxide
Q.Identify the type of chemical reaction
(i) A → B +C
(ii) AD +CD → AD +CB
(i) Decomposition reaction
(ii) Double displacement reaction
Q. Why does not silver evolve hydrogen on reacting with dil H2SO4
Silver do not evolve hydrogen on reacting with dil. H2SO4 as silver is less reactive
metal than hydrogen.
Q.Way do diamond and graphite, the two allotropic forms of carbon evolve different amounts of heat on combustion?
Diamond and graphite are the two allotropes of carbon but they do not evolve same amount of heat on combustion because they differ have different arrangement of carbon atoms and different shapes.
Q.What is the role of oxidizing agent is a reaction?
The oxidizing agent supply the oxygen in a reaction or removes the hydrogen.
Q.Write the balanced reactions for the following
(i) Potassium Bromide (aq) + Barium iodide (aq) → Potassium iodide (aq) + Barium Bromide(aq)
(ii) Zinc carbonate (s) → Zinc oxide (s) + carbon dioxide (g)
(iii) Hydrogen (g) + chlorine (g) → Hydrogen chloride
(i) 2KBr(aq) + BaI2 (aq) → 2KI (aq) + BaBr2 (aq)
(ii) ZnCO3 (s) → ZnO(s) +CO2 (g)
(iii) H2 (g) +Cl2 (g) →2HCl(g)
Q.The reaction is given by
Zn + H2 SO4 → ZnSO4 + H2
(i) Write the ionic equation for the reaction
(ii) The ionic equations can be represented by two half equations.Write these equations.
(iii) Explain why this is a redox reaction
(i) Zn +2H → Zn2+ + H2
(ii) The half ionic equations are-
Zn → Zn2+ + 2e–
2H+ + 2e– → H2
(iii) The first half represents oxidation and second half represents reduction. Therefore reaction is redox reaction.
Q.What are neutralization reactions? Why are they named so? Give one example?
A neutralization reaction is the chemical reaction between an acid and base For eg:- KOH(aq) + HNO3 (aq)→ KNO3 (aq) + H2O(aq)
It is called neutralization reaction because both 3 KNO3 and 2 H2O formed as the products, are neutral in nature.
What is a Chemical change:-
- It is the process of formation of new substances with new properties
- Examples are the fermentation of fruit, cooking of food, digestion of food, burning of fuel, respiration etc.
What is a Chemical reaction:-
- It is the chemical change in which new products are formed from old reactants.
- Those substances that take part in the chemical reaction are called reactant
- Those substances which are formed in the chemical reaction are called Product
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What is a chemical equation:-
- It is the representation of a chemical reaction by using symbols and formulae.
- Reactants are written in left side while product are written in right side.
- Reactant and Product are separated by single-headed arrow →
- Some examples are given below-
- Combustion of Hydrocarbons:
- CH4 (methane) + 2O2 → CO2 + 2H2O
- Rusting of Iron:
- 4 Fe + 3 O2 → 2 Fe2O3
- Photosynthesis:
- 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2
- Respiration:
- C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy
- Fermentation:
- C6H12O6 → 2 C2H5OH + 2 CO2
- Acid-Base Neutralization:
- HCl + NaOH → NaCl + H2O
- Precipitation Reaction:
- AgNO3 + NaCl → AgCl + NaNO3
- Hydrolysis of Salt:
- Na2CO3 + 2 HCl → 2 NaCl + H2O + CO2
- Oxidation of Hydrogen Peroxide:
- 2 H2O2 → 2 H2O + O2
- Decomposition of Hydrogen Peroxide:
- 2 H2O2 → 2 H2O + O2
- Synthesis of Water:
- 2 H2 + O2 → 2 H2O
- Electrolysis of Water:
- 2 H2O → 2 H2 + O2 (using electricity)
- Precipitation of Silver Iodide:
- 2 AgNO3 + KI → 2 AgI + 2 KNO3
- Formation of Ammonium Chloride:
- NH3 + HCl → NH4Cl
- Synthesis of Ammonia:
- N2 + 3 H2 → 2 NH3
- Esterification:
- CH3COOH + C2H5OH → CH3COOC2H5 + H2O
- Polymerization of Ethylene:
- n C2H4 → (C2H4)n (Polyethylene)
- Hydrogenation of Vegetable Oils:
- C18H36O2 + 3 H2 → C18H36O2 + 3 H2
- Saponification:
- Triglyceride + 3 NaOH → Glycerol + 3 Soap
- Ammonium Nitrate Decomposition (Explosive):
- NH4NO3 → N2 + 2 H2O + 1/2 O2
What is a Balanced and Unbalanced Chemical Equation?
- An equation having an equal number of atoms of different elements on the reactant as well as product side is called a Balanced chemical equation.
- An equation having an unequal number of atoms of different elements on the reactant as well as product side is called an Unbalanced chemical equation.
How many types of chemical reactions?
What is a Combination reaction?
- It is the reaction in which two or more reactant combine to form single product
- CaO + H2O → Ca(OH)2
What is a Decomposition reaction?
- It is the reaction in which single reactant is broken down to form two or more product
- 2 H2O → 2 H2 + O2 (using electricity)
What is a Single displacement reaction?
- It is the reaction where more reactive element displace less reactive element from the compound
- Zn + CuSO4 → FeSO4 + Cu
What is a Double displacement reaction?
What is a Redox reaction?
Redox reactions involve oxidation and reduction. The important concepts relating to redox reactions are:
I.Classical Concept: According to this concept oxidation is the process of addition of oxygen/electronegative element to a substance or removal of hydrogen/electropositive element from a substance.
Reduction is the process of removal of oxygen/electronegative element from a substance or addition of hydrogen/electropositive element to a substance.
Substance which is oxidised is called reducing agent and the substance which is reduced is called oxidising agent.
If oxidation and reduction take place simultaneously, the process is called Redox reaction.
i.e. reduction + oxidation → Redox reactions
E.g. Zn + CuO → ZnO + Cu
Here Zn is converted to ZnO. i.e oxygen is added to Zn. So it is oxidised and hence the reducing agent. CuO is
converted to Cu. i.e. oxygen is removed from Cu. So it is reduced and hence it is the oxidising agent.
Other examples are:
1. FeCl3 + H2 → FeCl2 + 2HCl
Here the electronegative Cl atom is removed from FeCl3. So it is reduced. H2 is oxidised since an
electronegative Cl atom is added to it. FeCl3 is the oxidising agent and H2 is the reducing agent.
2. 2 H2S(g) + O2 (g) → 2 S (s) + 2 H2O (l)
Here H2S is oxidised and O2 is reduced.
II. Electronic Concept: According to this concept oxidation is the process of removal (losing) of electron and reduction is the process of addition (gaining) of electron. A redox reaction is the process of exchange of electrons between two or more substances.
A substance that accepts electron is called oxidising agent and a substance that donates electron is called a reducing agent.
E.g. In the reaction Zn + Cu2+ → Zn2+ + Cu, Zn loses two electrons and forms Zn2+. So it is oxidised. Cu2+ gains two electrons and forms Cu. So it is reduced. Here Zn is the reducing agent and Cu2+ is the oxidising agent.
What is the Exothemic reaction?
What is the Endothermic reaction?
Corrosion
It is the process of formation of oxide or other compounds of metal on its surface by the action of air, water-vapor, CO2 etc.
Some common examples are The rusting of iron, tarnishing of silver, formation of a green coating on copper and bronze (verdigris) etc.
The most familiar example of corrosion is the rusting of iron. It occurs in the presence of water and air. It is a redox reaction.
At a particular spot of the metal, oxidation takes place and that spot behaves as the anode. Here Fe is oxidized to Fe2+.
2 Fe (s)→2 Fe2+ + 4 e–
Electrons released at anodic spot move through the metal and go to another spot on the metal and reduce oxygen in presence of H+ . This spot behaves as cathode. The reaction taking place at this spot is:
O2(g) + 4 H+(aq) + 4 e– ⎯→ 2 H2O (l )
The overall reaction is:
2Fe(s)+O2(g) + 4H+(aq) → 2Fe2 + (aq)+ 2 H2O (l )
The ferrous ions (Fe2+) are further oxidised to ferric ions (Fe3+) and finally to hydrated ferric oxide (Fe2O3. xH2O), which is called rust.
Methods to prevent corrosion
1. By coating the metal surface with paint, varnish etc.
2. By coating the metal surface with another electropositive metal like zinc, magnesium etc. The
coating of metal with zinc is called Galvanization and the resulting iron is called galvanized iron.
3. By coating with anti-rust solution.
4. An electrochemical method is to provide a sacrificial electrode of another metal (like Mg, Zn, etc.)
which corrodes itself but saves the object (sacrificial protection)
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