Multiple Choice Questions

Chemical Reactions and Equations

Updated for CBSE 2027
Board Exam Preparation
135+ Practice Questions
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Practice Questions with Answers

Total 135 questions available

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Q. 1
Dissolving suger is an example of
A
Physical change
B
None of these.
C
Redox Reaction
D
Chemical change
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Q. 2
AMg3N2 + bH2O → cMg(OH)2 + dNH3. When the equation is balanced, the coefficients a, b, c, d respectively are -
A
1, 6, 3, 2
B
1, 2, 3, 2
C
2, 3, 6, 2
D
1, 3, 3, 2
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Q. 3
Electrolysis of water is a decomposition reaction. The mole ratio of hydrogen and oxygen gases liberated during electrolysis of water is ________ .
A
4:1
B
2:1
C
1:2
D
1:1
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Q. 4
Write the balanced reaction of Calcium oxide with water and state what type of reaction is this
A
CaO + H2O→ Ca(OH)2, decomposition
B
CaO + H2O→ CaOH + H2, displacement
C
CaO + H2O→ CaOH, combination
D
CaO + H2O → Ca(OH)2, combination
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Q. 5
The reaction in which two compounds exchange their ions to form two new compounds is -
A
an isomerization reaction
B
a double displacement reaction
C
a displacement reaction
D
a decomposition reaction
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Q. 6
The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called:
A
corrosion
B
rancidity
C
reduction
D
antioxidation
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Q. 7
The reaction of H2 gas with oxygen gas to form water is an example of
A
all of these reactions
B
exothermic reaction
C
combination reaction
D
redox reaction
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Q. 8
What occurs in a decomposition reaction?
A
Formation of a single product
B
Breakdown of a single reactant into multiple products
C
Combination of multiple reactants into a single product
D
No change in reactants or products
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Q. 9
During the process of photosynthesis the catalyst is
A
glucose
B
CO2
C
chlorophyll
D
sunlight
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Q. 10
Which law governs the concept of balanced chemical equations?
A
Law of conservation of energy
B
Law of conservation of mass
C
Avogadro's law
D
Boyle's law
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Q. 11
When does a displacement reaction happen?
A
Two substances combine to form a single substance
B
A single substance decomposes to give multiple substances
C
Loss of hydrogen occurs
D
An element displaces another from its compound
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Q. 12
The formation of gas bubbles in a liquid during a reaction is called
A
deliquidizing
B
fuzzing
C
effervescence
D
bubbling
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Q. 13
Which of the following does not involve a chemical reaction?
A
Melting of candle wax on heating
B
Digestion of food in our body
C
Burning of candle wax when heated
D
Process of respiration
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Q. 14
A reaction of hydrogen with oxygen to form water is a
A
Exothermic reaction
B
Decomposition reaction
C
Endothermic reaction
D
Reaction not feasible
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Q. 15
Water breaks into its constituents
A
by passing electric current
B
by heating
C
by light
D
by magnetic effect
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Q. 16
What is the significance of balancing chemical equations?
A
To obey the law of conservation of mass
B
To increase reaction rates
C
To ensure reaction reversibility
D
To predict reaction outcomes
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Q. 17
CuSO4 + Zn → Cu + ZnSO4 This reaction is an example of a:
A
Displacement reaction.
B
Decomposition reaction.
C
Combination reaction.
D
Double displacement reaction.
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Q. 18
What is represented by symbols of elements and formulae of substances in chemistry?
A
Chemical reactions
B
Physical changes
C
Atomic structures
D
Molecular bonds
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Q. 19
What is oxidation?
A
Gain of oxygen or loss of hydrogen
B
Loss of oxygen or gain of hydrogen
C
Gain of hydrogen or loss of oxygen
D
Loss of hydrogen or gain of oxygen
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Q. 20
Name the component of our diet, decomposition of which produces the amino acid.
A
Protein
B
Starch
C
Carbohydrate
D
Fat
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Q. 21
What is the primary goal of balancing a chemical equation?
A
To alter the formulae of compounds
B
To change the reactants into products
C
To ensure conservation of mass
D
To increase the reaction rate
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Q. 22
When dilute HCl is added to zinc pieces taken in a test tube
A
A pungent smelling gas gets liberated.
B
small bubbles of H2 gas appear on the surface of zinc pieces
C
the colour of the solution becomes yellow.
D
No change takes place
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Q. 23
Which of the following reactions involves the combination of two elements ?
A
4Na + O2 → 2Na2O
B
SO2 + 1/2 O2 → SO3
C
NH3 + HCl → NH4Cl
D
CaO + CO2 → CaCO3
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Q. 24
The gas which turns lime water milky is
A
CO2
B
H2S
C
CO
D
SO
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Q. 25
In a balanced chemical equation, what remains constant?
A
Total number of atoms
B
Reactant mass
C
Product mass
D
Total number of molecules
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Q. 26
What happens when dilute Sulphuric acid is added to Zn granules? Tick the correct answer.
A
Zinc salt and water are produced)
B
Hydrogen gas and Zinc chloride are produced)
C
Chlorine gas and Zinc hydroxide are produced)
D
No reaction takes place.
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Q. 27
Magnesium ribbon is rubbed before burning because it has a coating of
A
basic magnesium sulphide
B
basic magnesium carbonate
C
basic magnesium chloride
D
basic magnesium oxide
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Q. 28
Which of the following reactions is an endothermic reaction ?
A
Decomposition of calcium carbonate to form quick lime and carbon dioxide.
B
Process of respiration.
C
Decomposition of vegetable matter into compost.
D
Burning of coal
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Q. 29
Lead nitrate Pb(NO3)2 on heating forms Lead oxide (PbO) solid and Nitrogen dioxide gas. What are the color of lead oxide and nitrogen dioxide?
A
Yellow, Colourless
B
White, Colourless
C
White, Brown
D
Yellow, Brown
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Q. 30
What happens to the number of products in a decomposition reaction?
A
Decreases
B
Increases
C
Remains the same
D
Reverses
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Q. 31
Which of the following reaction is not feasible?
A
Iron + Zinc sulphate solution
B
Copper + Zinc sulphate
C
Aluminium + Copper sulphate
D
Zinc + Copper sulphate solution
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Q. 32
A dilute ferrous sulphate solution was gradually added to the beaker containing acidified potassium permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?
A
KMnO4 is an unstable compound and decomposes in presence of FeSO4 to a colourless compound.
B
The colour disappears due to dilution; no reaction is involved.
C
FeSO4 acts as an oxidising agent and oxidises KMnO4
D
KMnO4 is an oxidising agent, it oxidises FeSO4
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Q. 33
AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq). Above reaction is
A
Combination reaction
B
Double Displacement reaction
C
Precipitation reaction
D
A and B both
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Q. 34
What type of reaction is respiration
A
Endothermic
B
Combination reaction
C
Reduction reaction
D
Exothermic
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Q. 35
Ethane (C2H6) on complete combustion gave CO2 and water. It shows that the results are in accordance with the law of conservation of mass. Then, the coefficient of oxygen is equal to
A
7/2
B
3
C
5/2
D
2
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Q. 36
Which of the following is true for an unbalanced chemical equation?
A
Number of atoms is less on the left side of the equation
B
Number of atoms is equal on both sides of the equation
C
Both (b) and (c).
D
Number of atoms is more on the right side of the equation
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Q. 37
Symbol Δ used while representing some chemical changes stands for -
A
catalyst
B
pressure
C
heat
D
light
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Q. 38
Oxidation is a process which involves
A
removal of hydrogen
B
addition of oxygen
C
addition of hydrogen
D
removal of oxygen
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Q. 39
Chemical equations balancing is in accordance with:
A
Law of constant proportions
B
Law of combining volumes
C
Law of conservation of mass
D
Both (a) and (c)
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Q. 40
In an electrolytic cell where electrolysis is carried, anode has:
A
Connected to negative terminal of the battery
B
None of these is correct
C
Positive change
D
Negative charge
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Q. 41
What happens when dilute hydrochloric acid is added to iron filling? Tick the correct answer:
A
Iron salt and water are produced
B
Hydrogen gas and iron chloride are produced.
C
Chlorine gas and iron hydroxide are produced
D
No reaction takes place
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Q. 42
Identify the correct chemical reaction.
A
Hydrogen sulphide gas burns in air to give water and sulphur.
B
Potassium metal reacts with water to give potassium hydroxide and water.
C
Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate
D
Zinc reacts with silver nitrate to form zinc nitrite and silver.
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Q. 43
What happens when dilute Sulphuric acid is added to Zn granules? Tick the correct answer.
A
Zinc salt and water are produced
B
No reaction takes place.
C
Hydrogen gas and Zinc chloride are produced
D
Chlorine gas and Zinc hydroxide are produced
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Q. 44
Identify the substances that are oxidised and the substances that are reduced in the following reactions. CuO(s) + H2(g)→ Cu(s) + H2O(l)
A
H2 is oxidised, CuO is reduced
B
CuO is oxidised, H2O is reduced
C
H2 is oxidised, H2O is reduced
D
Cu is oxidised, H2O is reduced
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Q. 45
Which of the following gases can be used for storage of fresh sample of an oil for a long time ?
A
Hydrogen
B
Helium
C
Nitrogen
D
Carbon dioxide
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Q. 46
When electricity is passed through water what kind of reaction takes place?
A
Electrolytic decomposition
B
Thermal decomposition
C
Displacement reaction
D
Photochemical decomposition
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Q. 47
When Ag is exposed to air it gets a black coating of
A
Ag2CO3
B
Ag2S
C
Ag2O
D
AgNO3
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Q. 48
Burning of the candle is a ________ change.
A
chemical
B
physical
C
none of these
D
both (a) and (b)
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Q. 49
The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called:
A
Reduction
B
Rancidity
C
Corrosion
D
Antioxidation
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Q. 50
How does the law of conservation of mass apply to chemical reactions?
A
It allows the creation of new substances
B
It prohibits the creation or destruction of matter
C
It permits the unequal distribution of mass in reactions
D
It encourages the loss of mass during reactions
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Q. 51
One of the following is an endothermic reaction. This is
A
Combination of nitrogen and oxygen to form nitrogen monoxide
B
Combination of glucose and oxygen to form carbon dioxide and water.
C
Combination of zinc and hydrochloric acid to form zinc chloride and hydrogen
D
Combination of carbon and oxygen to form carbon monoxide
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Q. 52
The balancing of chemical equations is in accordance with:
A
Law of constant proportions
B
Law of conservation of mass
C
Both b and c
D
Law of combining volumes
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Q. 53
The neutralization reaction between an acid and a base is a type of:
A
Addition reaction
B
Decomposition reaction
C
Double displacement reaction
D
Displacement reaction
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Q. 54
What characterizes a combination reaction?
A
Formation of a new single substance
B
Loss of hydrogen
C
Decomposition of a single substance
D
Formation of multiple substanc
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Q. 55
When ferrous hydroxide reacts with hydrochloric acid, ….. and H2O are produced
A
FeCl2
B
FeCl3
C
FeCl
D
FeCl4
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Q. 56
When green coloured ferrous sulphate crystals are heated, the colour of the crystal changes because
A
it forms SO3
B
it is decomposed to ferric oxide
C
it loses water of crystallisation
D
it forms SO2
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Q. 57
Heating of ferrous sulphate is a type of :
A
Decomposition reaction
B
Combination Reaction
C
Displacement reaction
D
All of the above
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Q. 58
What type of reaction involves the use of electrical energy for decomposition?
A
Thermal decomposition
B
Electrolytic decomposition
C
Photochemical decomposition
D
Chemical decomposition
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Q. 59
What occurs in a decomposition reaction?
A
Formation of a single substance
B
Formation of multiple substances
C
Decomposition of multiple substances
D
Loss of oxygen
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Q. 60
In a chemical reaction, if one of the product is a gas which burns with a ‘pop’, then the gas is
A
CO2
B
Cl2
C
O2
D
H2
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Q. 61
In photolysis, what form of energy is employed for decomposition?
A
Heat energy
B
Electrical energy
C
Sound energy
D
Light energy
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Q. 62
What type of reaction is respiration
A
Endothermic
B
Combination reaction
C
Reduction reaction
D
Exothermic
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Q. 63
Which of the following is the fastest reaction?
A
all the above
B
aluminium powder + NaOH
C
aluminium foil + NaOH
D
aluminium foil + NaOH + heat
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Q. 64
Give the ratio in which hydrogen and oxygen are present in water by volume.
A
1:2
B
1:1
C
2:1
D
1:8
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Q. 65
What is the primary characteristic of a decomposition reaction?
A
Breakdown of reactants into simpler substances
B
Formation of a single product
C
Combination of multiple reactants
D
Equal numbers of reactants and products
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Q. 66
Color of magnesium oxide is
A
Limestone
B
Quicklime
C
Slaked lime
D
Silver sulphide
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Q. 67
Which metal is displaced when lead is put in the solution of copper chloride ?
A
Copper
B
All of these
C
Lead
D
Chlorine
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Q. 68
How does the concept of balanced chemical equations relate to the law of conservation of mass?
A
It allows for the violation of the law of conservation of mass
B
It contradicts the law of conservation of mass
C
It has no relation to the law of conservation of mass
D
It demonstrates the validity of the law of conservation of mass
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Q. 69
What ensures equilibrium in chemical equations?
A
Reactant concentration
B
Product concentration
C
Balancing of atoms
D
Temperature
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Q. 70
On immersing an iron nail in CuSO₄ solution for a few minutes, you will observe
A
The color of solution fades away
B
The color of solution changes to green
C
The surface of iron nails acquire a black coating
D
No reaction takes place
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Q. 71
In the electrolysis of water, liquid water decomposes into its
A
two solid constituents
B
two gaseous constituents
C
one gaseous and one liquid constituent
D
two liquid constituents
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Q. 72
Which of the following is true for an unbalanced chemical equation?
A
The number of atoms is more on the right side of the equation
B
The number of atoms is less on the left side of the equation
C
The number of atoms is equal on both sides of the equation
D
Both (a) and (b)
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Q. 73
What are the new substances produced in a chemical reaction referred to as?
A
Molecules
B
Elements
C
Reactants
D
Products
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Q. 74
In a context of redox reactions, the removal of hydrogen from a substance is known as
A
Dehydrogenation
B
Reduction
C
Dehydration
D
Oxidation
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Q. 75
Which reaction uses electricity to decompose substances?
A
Thermal decomposition
B
Photochemical decomposition
C
Chemical decomposition
D
Electrolytic decomposition
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Q. 76
What remains constant in chemical reactions?
A
Temperature
B
Reactant concentration
C
Product concentration
D
Total number of atoms
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Q. 77
What is observed when a solution of potassium iodide is added to silver nitrate solution?
A
White precipitate of silver iodide is formed
B
Agl is soluble in water.
C
No reaction takes place
D
yellow precipitate of Agl is formed
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Q. 78
What does a balanced chemical equation indicate?
A
A reversible reaction
B
A spontaneous reaction
C
A quantitative reaction
D
A complete reaction
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Q. 79
Which form of energy is utilized in thermal decomposition reactions?
A
Light energy
B
Electrical energy
C
Heat energy
D
Chemical energy
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Q. 80
A student added dilute HCl to a test tube containing zinc granules and made following observations :
A
a gas evolved which burnt with a pop sound
B
the solution remained colourless
C
the solution becomes green in colour
D
the zinc surface became dull and black
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Q. 81
When S02 gas is passed through saturated solution of H2S, which of the following reaction occurs? A
A
SO2 + H2S → H2O + S
B
SO2 + H2O → SO3 + H2
C
SO2 + 2H2S → H20 + 3S
D
SO2 + 2H2S → 2H20 + 3S
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Q. 82
What is the name of the process where fatty foods become rancid?
A
Corrosion
B
Hydrogenation
C
Oxidation
D
Reduction
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Q. 83
When Mg ribbon is dipped in a test tube containing conc. HCI, products formed are
A
Mg+ H2
B
Mg + H2 + Cl2
C
Mg + Cl2
D
MgCl2 + H2
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Q. 84
Magnesium ribbon is cleaned before burning. Why?
A
It absorbs moisture from the atmosphere which interferes with burning.
B
All of the above
C
It’s outer layer form oxides which interfere with burning.
D
Dust from the atmosphere prevents its burning.
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Q. 85
In a chemical equation, what are the substances that undergo a reaction called?
A
Elements
B
Compounds
C
Reactants
D
Products
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Q. 86
Which of the following does not involve a chemical reaction?
A
Process of respiration
B
Digestion of food in our body
C
Melting of candle wax on heating
D
Burning of candle wax when heated
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Q. 87
Reaction in which heat energy is released is called
A
reversible
B
endothermic
C
exothermic
D
irreversible
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Q. 88
What ensures a balanced chemical equation?
A
Equal reactant and product volumes
B
Equal reactant and product masses
C
Equal number of atoms of different elements
D
Equal number of molecules in reactants and products
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Q. 89
Which of the following is not physical change?
A
Combustion of Liquefied Petroleum Gas (LPG)
B
Dissolution of salt in water
C
Melting of ice to give water
D
Boiling of water to give water vapour
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Q. 90
Which principle states that matter cannot be created or destroyed in a chemical reaction?
A
Law of conservation of energy
B
Law of conservation of mass
C
Law of definite proportions
D
Law of multiple proportions
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Q. 91
What does the symbol":"represent in a chemical reaction ?
A
Precipitate formed
B
Gas released
C
Solid state
D
Direction of reaction
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Q. 92
The balancing of chemical equations is in accordance with:
A
Law of constant proportions
B
Law of conservation of mass
C
Both b and c
D
Law of combining volumes
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Q. 93
A solution of a substance ‘X’ is used for white washing. Name the substance ‘X’ and write its formula)
A
Calcium oxide , CaO
B
Lime stone, CaCO3
C
Calcium carbonate , CaCO3
D
Lime , CaCO3
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Q. 94
Solubility of a solute
A
remains constant
B
none of these
C
increases with temperature
D
decreases with temperature
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Q. 95
Which law should be kept in mind while we balance chemical equations?
A
Conservation of frequency
B
Conservation of momentum
C
Conservation of energy
D
Conservation of mass
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Q. 96
Which of the following statements is/are correct ?
A
A chemical equation tells us about the atoms or molecules of the reactants and products involved in a reaction.
B
A chemical equation informs us about the symbols and formulae of the substances involved in a reaction.
C
A chemical equation tells us about the substances involved in a reaction.
D
All the above
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Q. 97
H2S + Cl2 ® 2HCI + S In the above reaction, the gaseous reactants produce
A
one gaseous and one solid product
B
one liquid and one solid product
C
one gaseous and one liquid product
D
two solid products
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Q. 98
Which one of the following processes involves a chemical reaction?
A
Storing of oxygen gas under pressure in a gas cylinder
B
Heating copper wire in presence of air at high temperature
C
Liquification of air
D
Keeping petrol in a china dish in the open
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Q. 99
In our body the catalyst which helps to break down food is
A
hormones
B
dil HCI
C
NaOH
D
digestive enzymes
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Q. 100
What is reduction?
A
Gain of oxygen or loss of hydrogen
B
Loss of oxygen or gain of hydrogen
C
Gain of hydrogen or loss of oxygen
D
Loss of hydrogen or gain of oxygen
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Q. 101
Which of the folllowing is an example of simple displacement?
A
the reaction of a metal with an acid
B
The reaction of two salt solutions to form a precipitate
C
the burning of methane
D
the electrolysis of water
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Q. 102
Fill in the blank in the chemical equation : ……. + 4HNO3 → Cu(NO3)2 + 2NO2 + 2H2O
A
CuO
B
Cu
C
2CuO
D
2Cu
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Q. 103
In the balanced equation Na2CO3 + xHCl → 2NaCl + CO2 + H2O. The value of x is
A
2Al + 6H2O → 2Al(OH)3 + 3H2
B
4NH3 + 5O2 → 4NO + 6H2O
C
2C4H10 + 12O2 → 8CO2 + 10H2O
D
2NaHCO3 → Na2CO3 + H2O + CO2
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Q. 104
The reaction which decomposes after the supply of heat is called
A
Displacement reaction
B
Redox reaction
C
Thermal decomposition
D
Combination reaction
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Q. 105
What does an unbalanced chemical equation lack?
A
Reactants
B
Products
C
Equal numbers of atoms
D
Molecular bonds
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Q. 106
In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution:
(i) exchange of atoms takes place.v (ii) exchange of ions takes place.v (iii) a precipitate is produced.
(iv) an insoluble salt is produced.
The correct option is :
A
only (ii)
B
(ii), (iii) and (iv)
C
(ii) and (iv)
D
(i) and (iii)
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Q. 107
In balancing a chemical equation, what remains constant?
A
Total mass
B
Reactant concentration
C
Product composition
D
Total number of atoms
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Q. 108
In which of the following, the identity of initial substance remains unchanged?
A
Digestion of food
B
Formation of crystals by process of crystallisation
C
Fermentation of grapes
D
Curdling of milk
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Q. 109
The chemical reaction between two substances is characterized by a change in colour from Orange to green. These two substances are most likely to be
A
Potassium dichromate solution and carbon dioxide
B
Potassium permanganate solution and lemon juice
C
Potassium permanganate solution and Sulphur dioxide
D
Potassium dichromate solution and Sulphur dioxide
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Q. 110
Pb(NO3)2 which is colourless, reacts with H2S to give a precipitate of PbS, whose colour is
A
white
B
green
C
brown
D
black
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Q. 111
Which of the following is not a displacement reaction?
A
Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
B
Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride
C
Aluminium + Copper chloride → Aluminium chloride + Copper
D
Potassium bromide (aq) + Barium iodide(aq) → Potassium iodide(aq) + Barium bromide(s)
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Q. 112
What does the law of conservation of mass imply about chemical reactions?
A
Mass is always conserved in chemical reactions
B
Mass can be created during reactions
C
Mass can be destroyed during reactions
D
Mass is only conserved in certain reactions
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Q. 113
Which one of the following precipitates are formed when the carbon dioxide gas is passed through lime water?
A
Ca(OH)4
B
Ca(OH)2
C
CaCO₂
D
CaCO3
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Q. 114
A compound used for whitewashing is
A
Quick lime
B
Blue vitriol
C
Limestone
D
Slaked Lime
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Q. 115
Silver article turns black when kept in the open for a few days due to formation of
A
Ag2S
B
H2S
C
AgSO4
D
AgS
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Q. 116
How are reactants and products represented in a chemical equation?
A
By symbols of elements
B
By molecular weights
C
By atomic numbers
D
By structural formulas
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Q. 117
Which of the following reaction will evolve hydrogen gas with a pop sound?
A
Concentrated nitric acid is reacted with sulphur.
B
A small piece of zinc is added to dilute hydrochloric acid
C
Ammonia is passed over heated copper (II) oxide.
D
Lead Nitrate is heated strongly in a test tube.
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Q. 118
The process of reduction involves
A
removal of hydrogen
B
removal of oxygen
C
addition of oxygen
D
addition of hydrogen
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Q. 119
Which of the following is not conveyed by a balanced chemical equation?
A
If a particular reaction is practically feasible or not.
B
Symbols and formulae of all the reactants.
C
Number of atoms and molecules of the products formed.
D
The physical state of reactants and products.
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Q. 120
In the decomposition of NH4CI, the products formed are
A
NH3 + HCI
B
H2 + Cl2
C
N2 + HCI
D
N2 + Cl2
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Q. 121
Redox reactions are useful in
A
bleaching industry
B
extraction of metals
C
dying industry
D
all of these
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Q. 122
Zn + HCl → ZnCl₂ + _________ .
A
Zn
B
H₂
C
None of these
D
Cl₂
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Q. 123
In the equation, a Al + bH2SO4 → c Al2(SO4)3 + dH2 a, b, c, d are respectively -
A
2, 3, 1, 3
B
2, 3, 2, 3
C
2, 3, 1, 1
D
2, 2, 3, 3
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Q. 124
Rancidity can be prevented by:
A
storing food away from light
B
keeping food in refrigerator
C
adding antioxidants
D
all of the above
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Q. 125
A substance added to food containing fats and oils is called:
A
Rancid
B
Oxidant
C
Antioxidant
D
Coolant
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Q. 126
A catalyst when added to a chemical reaction changes the
A
physical state of the products
B
speed of the reaction
C
A catalyst when added to a chemical reaction changes the
D
colour of the reactants
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Q. 127
Which type of reaction is the opposite of a combination reaction?
A
Thermal decomposition
B
Electrolytic decomposition
C
Decomposition reaction
D
Photolysis
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Q. 128
Which of the following is a physical change?
A
Getting salt from sea water
B
Burning of wood
C
Ripening of fruits
D
Formation of curd from milk
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Q. 129
A solution of a substance ‘X’ is used for white washing. Name the substance ‘X’ and write its formula)
A
Calcium oxide , CaO
B
Calcium carbonate , CaCO3
C
Lime , CaCO3
D
Lime stone, CaCO3
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Q. 130
The blue flame in the below image represents the burning of which metal?
A
All metal burn to give a blue flame
B
Sodium
C
Copper
D
Iron
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Q. 131
The oxidation reaction which produces heat and light is called:
A
Photochemical
B
Endothermic
C
Exothermic
D
Combustion
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Q. 132
Assertion: Zinc reacts with sulphuric acid to form zinc sulphate and hydrogen gas and it is displacement reaction.
A
Both A and R are true but R is not the correct explanation of (a)
B
A is false but R is true.
C
Both A and R are true and R is the correct explanation of (a)
D
A is true but R is false.
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Q. 133
Name the products formed when iron filings are heated with dilute hydrochloric acid
A
Fe (II) chloride and water
B
Fe (III) chloride and water
C
Fe (III) chloride and hydrogen gas
D
Fe (II) chloride and hydrogen gas
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Q. 134
What is the primary requirement for a chemical equation to be balanced?
A
Equal product concentrations
B
Equal reactant concentrations
C
Equal product masses
D
Equal numbers of atoms on both sides
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Q. 135
To facilitate the electrolysis of water we add a few drops of acids like sulfuric acid or salts like NaCl. Because:
A
It prevents the decomposition of electrodes used.
B
It increases the electrical conductivity of water.
C
None
D
It acts as a catalyst
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