CHEMICAL REACTIONS AND EQUATIONS STAND ALONE MCQs
(1 Mark each)
Q. 1. Which of the following is not a physical change?
(A) Boiling of water to give water vapour
(B) Melting of ice to give water
(C) Dissolution of salt in water
(D) Combustion of liquified petroleum gas (LPG)
Ans. Option (D) is correct.
Explanation: During combustion of liquified
petroleum gas (LPG), it forms CO₂, and H₂O.
(B) 2H₂(g) + O₂(l)→ 2H₂O(l)
Q. 2. Which one of the following processes involve chemical reactions?
(A) Storing of oxygen gas under pressure in a gas cylinder.
(B) Liquification of air.
(C) Keeping petrol in a china dish in the open
(D) Heating copper wire in presence of air at high temperature.
Ans. Option (D) is correct.
Explanation: Chemical changes involve
formation of new compounds from one or
more substances. On heating copper wire in
presence of air at high temperature copper (II) oxide is formed.
Q. 3. In which of the following chemical equations, the abbreviations represent the correct states of
the reactants and products involved at reaction
temperature?
(A) 2H₂(g)+ O(l)→ 2H₂O(g)
(B) 2H₂(g) + O₂(l) → 2H₂O(l)
(C) 2H₂(g) + O₂(g) → 2H₂O(l)
(D) 2H₂(g) + O₂(g) → 2H₂O(g)
Ans. Option (C) is correct.
Explanation: It is because, the standard state
for hydrogen and oxygen is gas and for water is liquid at reaction temperature.
Q. 4. The reaction in which a substance or substances undergo change to produce new substances with new properties is called
(A) A biochemical reaction
(B) A nuclear reaction
(C) A physical reaction
(D) A chemical reaction
Ans. Option (D) is correct.
Explanation: A reaction in which a substance is changed to one or more new substances is
called a chemical reaction.
Q.5. Which of the following conditions is necessary for a chemical reaction?
(A) It must be accompanied with change in
temperature and pressure.
(B) At least one of the reactants must be in a fixed quantity.
(C) It must follow the law of conservation of mass
(D) All of the above.
Ans. Option (C) is correct.
Explanation: A chemical reaction must follow the law of conservation of mass.
Science Mcq Class 10 CHEMICAL REACTIONS AND EQUATIONS
Q.6. There is an equation X, which contains equal
sides. number of atoms of each element on both What is 'X'?
(A) A balanced equation
(B) An unbalanced equation
(C) A chemical equation
(D) All of the above
Ans. Option (A) is correct.
Explanation: A balanced equation is the one in which the atoms of every element will be the same on both the sides of the equation.
Q. 7. Which among the following is not a physical change?
(A) Evaporation of petrol
(B) Burning of liquified petroleum gas (LPG)
(C) Heating of an iron rod to red hot.
(D) Sublimation of solid ammonium chloride
Ans. Option (B) is correct.
Explanation: Changes which are temporary
with no new substance being formed, are
known as physical changes. Change in which one or more new substances are formed is known as chemical change.
Q. 8. In the given equation, what does X stand for?
(2)AI + (X)H₂SOAL (SO) + (3)H₂
(A) 2
(B) 3
(C) 1
(D) 5
Ans. Option (B) is correct.
Explanation: The X value is 3 because, to
balance the given equation, the number of
atoms of each element should be same on both the sides.
2AI + (3)H₂SO₄→Al₂(SO₄)₃ + 3H₂
Q. 9. Which of the following reactions is an endothermic reaction?
(A) Burning of coal.
(B) Decomposition of vegetable matter
into compost.
(C) Process of respiration.
(D) Decomposition of calcium carbonate to form quick lime and carbon dioxide.
(Board SQP, 2020)
Ans. Option (D) is correct.
Explanation: The reactions which require energy in the form of heat, light or electricity to break reactants are called endothermic reactions.
Q. 10. The following reaction is an example of a
4NH₂(g) + 5O₂(g) →4NO(g) + 6H₂O(g)
(i) Displacement reaction
(ii) Combination reaction
(iii) Redox reaction
(iv) Neutralisation reaction
(A) (i) and (iv)
(B) (ii) and (iii)
(C) (i) and (iii)
(D) (iii) and (iv)
Ans. Option (B) is correct.
Explanation: The given reaction is a redox
reaction because oxidation and reduction.
both take place simultaneously. Also, it is a
displacement reaction because hydrogen of
NH, has been displaced by oxygen.
Q. 11. Three beakers labelled as A, B and C each containing 25 ml. of water were taken. A small amount of NaOH, anhydrous CuSO₄ and NaCl were added to the beakers A, B and C respectively. It w as observed that there was an increase in the temperature of of the solutions contained in beakers A and B, whereas in case of beaker C, the temperature. of the solution falls. Which one of the following statement(s) is (are) correct?
(1) In beakers A and B, exothermic process has occurred.
(ii) In beakers A and B, endothermic process has
occurred.
(iii) In beaker C, exothermic process has occurred.
(iv) In beaker C, endothermic process has occurred.
(A) (i) only
(B) (ii) only:
(C) (i) and (iv)
(D) (ii) and (ii)
Option (C) is correct.
Explanation: In beakers A and B, heat is
given out, so the temperature of the solution
increases, hence it is an exothermic reaction
while in beaker C, heat is absorbed from water,
so temperature falls, hence it is an endothermic
process.
Science Mcq Class 10 CHEMICAL REACTIONS AND EQUATIONS
Q. 12. A dilute ferrous sulphate solution was gradually added to the beaker containing acidified 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 s an oxidising agent, it oxidises FeSO₄
(B) FeSO₄ acts as an oxidising agent and oxidises KMnO₄
(C) The colour disappears due to dilution; no
reaction is involved.
(D) KMnO₄ is an unstable compound and
decomposes in presence of FeSO₄ to a
colourless compound.
Ans. Option (A) is correct.
Explanation: A dilute ferrous sulphate
solution was gradually added to the beaker
containing acidified permanganate solution.
A permanganate solution is usually purple in
colour. The light purple colour of the solution
fades and finally disappears. This is because
potassium permanganate (KMnO₄) is relatively
an unstable compound, it tends to decompose
in the presence of ferrous sulphate (FeSO₄)
This changes the colour of the solution from
purple to colourless. FeSO₄ gets oxidised to
Fe₂(SO₄)₃ as KMnO4 acts as a good oxidising
agent in an acidic medium,
Q.13. Which among the following displacement reaction(s)?
(1) Pb+ CuCl₂ →+ PbCl₂ + Cu
(ii) Na₂SO₄ + BaCl₂ → BaSO₄ +2NaCl
(iii) C + O₂ → CO₂
(iv) CH₃ +2O₂ → CO₂ + 2H₂O
(A) (i) and (iv)
(B) (ii) only
(C) (i) and (ii)
(D) (iii) and (iv)
Ans. Option (B) is correct.
Explanation: Double displacement reaction is
the reaction in which two different atoms or
group of atoms are mutually exchanged. In this
reaction Na₂SO₄ + BaCl₂ → BaSO₄ +2NaCl,
sodium and barium were mutually exchanged.
Q. 14. Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?
(1) Displacement reaction
(ii) Precipitation reaction
(iii) Combination reaction
(iv) Double displacement reaction
(A) (1) only
(B) (ii) only
(C) (iv) only
(D) (i) and (iv)
Ans. Option (D) is correct.
Explanation: The reaction is double a displacement reaction as:
BaCl₂ + (NH₄)₂SO₄→ BaSO₄ + 2NH₄Cl
It is also called precipitation reaction due to
the formation of white precipitate of barium
sulphate.
Science Mcq Class 10 CHEMICAL REACTIONS AND EQUATIONS
Q.15. What happens when dilute hydrochloric acid is added to iron filings? Choose the correct answer.
(A) Hydrogen gas and iron chloride are produced.
(B) Chlorine gas and iron hydroxide are produced.
(C) No reaction takes place.
(D) Iron salt and water are produced.
Ans. Option (A) is correct.
Explanation: When dilute hydrochloric acid
is added to iron filings, hydrogen gas and
iron chloride are produced. The reaction is as
follows:
Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂
Q. 16. Which among the following statement(s) is (are) true? Exposure of silver chloride to sunlight for a long duration turns grey due to
(i) The formation of silver by decomposition of
silver chloride
(ii) Sublimation of silver chloride
(iii) Decomposition of chlorine gas from silver
chloride
(iv) Oxidation of silver chloride
(A) (i) only
(B) (1) and (ii)
(C) (ii) and (iii)
(D) (iv) only
Ans. Option (A) is correct.
Explanation: In the presence of sunlight, the
heavy amount of energy of light decomposes
AgCl to silver (Ag) and chloride (Cl) ions.
The silver flakes are truly black which when
fully spread over white silver chloride looks
grey.
ASSERTION AND REASON BASED MCQs for CBSE CLASS 10TH SCIENCE
Directions In the following questions, A statement of Assertion (A) is followed by a statement of Reason (R). Mark the correct choice as.
(A) Both A and R are true and R is the correct explanation of A.
(B) Both A and R are true but R is NOT the correct explanation of A.
(C) A is true but R is false.
(D) A is false and R is true.
Q. 1. Assertion (A): Carbon dioxide turns lime water milky.
Reason (R): Carbon dioxide sullies the water.
Ans. Option (C) is correct.
Explanation: Carbon dioxide reacts with lime water (calcium hydroxide) to form milky precipitate of calcium carbonate.
Q. 2. Assertion (A): A chemical reaction becomes faster at higher temperatures.
Reason (R): At higher temperatures, molecular
motion becomes more rapid.
Ans: Option (A) is correct.
Explanation: A chemical reaction becomes faster at higher temperatures because at high temperature, the movement of particles are greater
Q.3. Assertion (A): After white washing the walls, a shiny white finish on walls is obtained after two to three days
Reason (R): Calcium hydroxide reacts with carbon dioxide to form calcium hydrogen carbonate which
gives shiny white finish.
Ans. Option (C) is correct.
Q. 4. Assertion (A): Burning of candle is a physical change.
Reason (R): In physical change, no new substance is formed.
Ans. Option (D) is correct.
Explanation: Burning of candle is chemical
change. Burning of candle melts the wax and
hence physical state of wax has changed from
solid to liquid. Again the wax combines with
the atmosphere oxygen and changes to carbon
dioxide, heat and light.
Q.5. Assertion (A): Sodium metal is stored under kerosene.
Reason (R): Metallic sodium melts when exposed to air.
Ans. Option (C) is correct.
Explanation: Sodium is a very reactive metal.
It is kept in kerosene to prevent it from coming
in contact with oxygen and moisture. If this
happens, it will react with the moisture present
in air and form sodium hydroxide. This is a
strongly exothermic reaction, and lot of heat is
generated.
Q. 6. Assertion (A): To dilute sulphuric acid, acid is added to water and not water to acid.
Reason (R): Specific heat of water is quite large.
Ans. Option (A) is correct.
Explanation: The mixing of water to an acid is highly exothermic in nature. If water is added to art acid it produces very large amount of heat which can break the container and some times even causes burning. So it is advised to add concentrated acid to water in very slow manner.
0.7. Assertion: In the reaction:
MnO₂ + 4HCI →MnCl₂ + 2H₂O + Cl₂
HCI is getting oxidized while MnO, is getting reduced.
Reason: The process in which oxygen is added to a substance is called oxidation.
whereas the process in which oxygen is removed from a substance is called reduction.
Ans. Option (A) is correct.
Explanation: In the given reaction, HCI is oxidized to Cl, while MnO, is reduced to MnCl₂
Q.8. Assertion (A): Chips manufacturers usually flush bags of chips with gas such as nitrogen. Reason (R): Nitrogen gas prevents the oil and fats of the chips from being oxidized
Ans. Option (A) is correct.
Explanation: Chips manufacturers usually flush bags of chips with gas such as nitrogen to prevent the oil and fats of the chips from being oxidized or become rancid.
Attempt any 4 sub-parts from each question.. Each sub-part carries 1 mark.
Read the following and answer any four questions [CBSE QB 2021]
from Q.1. to Q.5.
Marble's popularity began in ancient Rome and
Greece, where white and off-white marble were used to construct a variety of structures, from hand held sculptures to massive pillars and buildings.
Q. 1. The substance not likely to contain CaCO is
(A) Dolomite
(B) A marble statue
(C) Calcined gypsum
(D) Sea shells,
Ans. Option (C) is correct.
Explanation: The composition of gypsum is
CaSO₄ + 2H₂O. It does not have CaCO₃
Q. 2. A student added 10g of calcium carbonate in a rigid container, secured it tightly and started to heat it. After some time, an increase in pressure was observed, the pressure reading was then noted at intervals of 5 minutes and plotted against time, in a graph as shown below. During which time interval did maximum decomposition took place?
(A) 15-20 min
(B) 10-15 min
(C) 5-10 min
(D) 0-5 min
Ans. Option (D) is correct.
Explanation: The maximum decomposition is when the pressure is maximum. As we can see in graph that from 0 to 5 minutes, the pressure increases from 0 to 0.625 atm.
Q. 3. Gas A, obtained above is a reactant for a very important biochemical process which occurs in the presence of sunlight. Identify the name of the process -
(A) Respiration
(C) Transpiration
(B) Photosynthesis
(D) Photolysis
Ans. Option (B) is correct.
Explanation: When CaCO3 is heated, the following reaction takes place: CaCO3 —» CaO + CO, The gas evolved is carbon dioxide, which is utilised in the process of photosynthesis.
Q. 4. Marble statues are corroded or stained rain water. Identify the main reason.
(A) decomposition of calcium carbonate to calcium. oxide
(B) polluted water is basic in nature hence it reacts with calcium carbonate
(C) polluted water is acidic in nature he
(D) calcium carbonate dissolves in water to give
calcium hydroxide.
Ans. Option (B) is correct.
Explanation: Chemically, marble is Calcium Carbonate The atmosphere contains many oxides, which t
dissolve in water forming acids like sulfuric
nitric which are common due to modern
pollution. Even carbon dioxide forms carbonic
acid which also does damage. These will react with marble and result in
formation of calcium salt, carbon dioxide and i
water. So, under extended periods, the wear of
marble statues is expected.
Q. 5. Calcium oxide can be reduced to calcium, by heating with sodium metal. Which compound would act as an oxidizing agent in the above process?
(A) sodium
(C) calcium
(B) sodium oxide
(D) calcium coide.
Ans. Option (D) is correct.
Explanation: A substance that tinderges reduction is an modizing agent. Here, CaO is losing oxygen and underguing reduction. So, CaO is the oxdizing agent
from Q.1. to Q.5.
Chemistry in Automobiles For an internal combustion engine to move a vehicle down the road, it must convert the energy stored in the fuel into mechanical energy to drive the wheels In your car, the distributor and battery provide this starting energy by creating an electrical "spark, which helps in combustion of fuels like gasoline. Below is the reaction depicting complete combustion of gasoline in full supply of air.
2C8H18(l) +250₂(g)- →16 'X' + Y
Q. 1. Which of the following are the products obtained from the reaction mentioned in the above case? Product 'X' Product 'Y'
(A) CO₂ H₂O₂
(B) H₂O CO
(C) CH3OH H₂O
(D) CO₂ H₂O
Ans. Option (D) is correct.
Explanation: The complete combustion of gasoline in full supply of air results in production of carbon dioxide and water. The chemical reaction is as follows:
2C8H18 (l) +250₂(g) →16CO2(g) + 18J₂P(g)
Q. 2. Identify the types of chemical reaction occurring during the combustion of fuel:
(A) Oxidation & Endothermic reaction tow
(B) Decomposition & Exothermic reaction
(C) Oxidation & Exothermic reaction
(D) Combination & Endothermic reaction Ans. Option (C) is correct.
To Explanation: The addition of oxygen to a substance or removal of hydrogen from a substance is called oxidation. The reaction in which the heat energy is produced is called 10 exothermic reaction.
Q. 3. On the basis of evolution/absorption of energy, which of the following processes are similar to combustion of fuels.
(i) Photosynthesis in plants
(ii) Respiration in the human body
(iii) Decomposition of vegetable matter
(iv) Decomposition of ferrous sulphate.
(A) (ii) & (iii)
(C) (iii) & (iv)
(B) (i) & (ii) (D) (ii) & (i) oil
Ans. Option (A) is correct.
Explanation: The process of respiration in the human body and decomposition of vegetable matter involves evolution of energy.
Q. 4. 'A student while walking on the road observed that a cloud of black smoke belched out from the exhaust stack of moving trucks on the road.' Choose the correct reason for the production of black smoke:
(A) Limited supply of air leads to incomplete combustion of
(B) Rich supply of air leads to complete combustion of fuel.
(C) Rich supply of air leads to a combination reaction.
(D) Limited supply of air leads to complete combustion of fuel.
Ans. Option (A) is correct.
Explanation: The limited supply of air leads to incomplete combustion of fuel, which in turn leads to the production of black smoke.
5. Although nitrogen is the most abundant gas in the atmosphere, it does not combustion'. Identify the correct reason for this statement.
(A) Nitrogen is a reactive gas
(B) Nitrogen is an inert gas
(C) Nitrogen is an explosive gas
(D) Only hydrocarbons can take part in combustion
Ans. Option (B) is correct.
Explanation: The triple bond in nitrogen is too strong to be broken and hence it is an inert gas which does not take part in combustion.
III. Read the given passage and answer any four
Questions from Q.1 to Q.5.
The physical states of the reactants and products can be represented by using the symbols (s) for solids, (l) for liquids, (g) for gases and (aq) for aqueous solution along with their respective formulae. The word aqueous is written if the reactant or product is present as a solution in water. Precipitate can also be represented by using an arrow pointing downwards (↓) instead of using symbol (s).
In the same way, the gaseous state of an evolved gas can be represented by using an arrow pointing upward direction (↑) instead of using symbol (g). The specific condition of the reaction like temperature, pressure, catalyst etc. is written above or below the arrow in the chemical equation.
2. 1. If the reactant or product is present as a solution of water, it is represented as:
(A) (s)
(B) (1)
(C) (aq)
(D) ↓
Ans. Option (C) is correct.
Explanation: The word aqueous is written if the reactant or product is present as a solution in water.
2. 2. The correct way to represent the evolution of is gas, to use which of the following symbol: (A) ↓
(B) →→→
(C) ↑
(D) (g)
Ans. Option(C) is correct.
Explanation: The gaseous state of an evolved gas can be represented by using an arrow pointing upward direction (1) instead of using symbol (g).
Q. 3. Complete the missing variable given as X and Y in the following reaction:
2Na (s) + 2H₂O (1)→ 2NaOH (X) + H₂ (Y)
(A) (aq) and (g)
(B) (s) and (g)
(C) (g) and (1)
(D) (g) and (aq)
Ans. Option (A) is correct.
Explanation: Explanation: The complete reaction is:
2Na(s) + 2H₂O (1)→ 2NaOH(s) + H₂(g)
@@@@@@@@@
Q. 4. Which of the following reaction is balanced?
(A) NaCl + 2H₂O → 2NaOH + 2Cl₂ + H₂
(B) 2NaCl + H₂O → 2NaOH + 2Cl₂ + H₂
(C) 2NaCl + 2H₂O → 2NaOH + Cl₂ + H₂
(D) 2NaCl + 2H₂O → NaOH + Cl₂ + H₂
Ans. Option (C) is correct.
Explanation: The equation in which atoms of various elements on both sides of a chemical equation are equal in accordance with the law of conservation of mass are said to be balance. Hence, 2NaCl + 2H₂O- →→→2NaOH + Cl₂ + H₂ represents the correct balanced equation.
Q. 5. Which of the following reaction is balanced?
(A) Mg (aq) + H₂SO4 (aq) → MgSO4 (aq) + H₂↑
(B) Mg (s) + H₂SO4 (aq) → MgSO4 (aq) + H₂ ↑
(C) Mg (s) + H₂SO4 (1)→ MgSO4 (1) + H₂(g)
(D) Mg (s) + H₂SO4 (1)→ MgSO4 (s) + H₂ Ans. Option (B) is correct.
Explanation: Mg (s) + H₂SO4 (aq) →→→→→→ MgSO4 (aq) + H₂ T is the balanced chemical reaction. A balanced equation is the one in which the atoms of every element will be the same on both the sides of the equation.
IV. Read the given passage and answer any four questions from Q.1 to Q.5.
In the following chemical reaction "zinc oxide reacts with carbon to produce zinc metal and carbon monoxide." Answer any four question from (1) to (5).
Q. 1. Name the substance getting oxidised and reduced in the above reaction:
(A) C and ZnO
(B) Zn and C
(C) ZnO and CO
(D) CO and ZnO
Ans. Option (A) is correct.
Explanation: C is getting oxidized to CO, ZnO is getting reduced to Zn, as carbon is gaining oxygen and ZnO is losing oxygen.
Q. 2. Name the type of reaction:
(A) oxidation reaction
(B) reduction reaction
(C) redox reaction
(D) decomposition reaction
Ans. Option (C) is correct.
Explanation: It is a redox reaction or oxidation
and reduction reaction.
Q. 3. The reduction reaction involves:
(A) gain of electrons
(B) loss of electrons
(C) increase in oxidation state
(D) addition of oxygen
Ans. Option (A) is correct.
Explanation: Reduction is just reverse of oxidation. It is the process of gain of electron and losing oxygen or gaining hydrogen.
Q. 4. The reactions used in black white photography:
(A) Decomposition of silver bromide
(B) Decomposition of silver chloride (C) Both
(D) None of the above
Ans. Option (C) is correct.
Explanation: Decomposition reactions of
silver chloride and silver bromide in presence of sunlight are used in black and white photography.
2AgCl(s)- → 2Ag(s) + Cl₂(g)
2AgBr 2Ag + Br₂
V. P, Q and R are three elements which undergo chemical reactions according to the following equations. Answer any four question from Q.1 to
Q.5.
(i) P₂O3 +2Q→→ Q₂O3 + 2P
(ii) 3RSO4 + 2Q →→ Q₂(SO4)3 + 3R
(iii) 3RO+2P→ P₂O3 + 3R
Q. 1. The most reactive and the least reactive elements are:
(A) Q and P
(B) Q and R
(C) R and Q
(D) R and P
Ans. Option (B) is correct.
Explanation: Q is the most reactive as it has replaced both P and R from their compounds and R is least reactive element as it has been replaced by both P and Q.
Q. 2. The type of reaction is:
(A) Displacement reaction (B) Combination reaction
(C) Neutralisation reaction
(D) Substitution reaction
Ans. Option (A) is correct.
Explanation: Displacement reaction is a type of reaction in which more active element displaces a less reactive element from its compound.
Q.3.3RSO4 + 2Q Q2(SO4)3 + 3R
The given reaction shows:
(A) Q is more reactive than R
(B) Q is less reactive than R
(C) Q and R are equally reactive
(D) none of the above
Ans. Option (A) is correct.
Explanation: The given reaction shows that Q is the most reactive as it has replaced both P and R from their compounds.
Q. 4. Choose the correct statement:
(A) Zinc and lead are more reactive elements than copper.
(B) Zinc and lead are less reactive elements than copper.
(C) Zinc and copper are more reactive elements than lead.
(D) Copper and lead are more reactive elements than zinc. Ans. Option
(A) is correct.
Explanation: A more reactive metal has a tendency to get oxidized and a less reactive metal ion has a tendency to get reduced. Therefore, a more reactive metal displaces a less reactive metal from its salt solution.
Q. 5. Na₂SO4 (aq) + BaCl₂(aq) → BaSO4 (s) + 2NaCl(aq)
The above reaction is an example of:
(A) Double displacement reaction.
(B) Displacement reaction.
(C) Can be both.
(D) None of the above.
Ans. Option (A) is correct.
Explanation: Double displacement reaction is a reaction in which two different ions or group of atoms in the reactant molecules are displaced by each other. Na being more reactive than Ba²+ displaces Ba²+ from its compound BaCl₂ and form NaCl.
VI. The following diagram displays a chemical reaction. Observe carefully and answer any four
questions from Q.1 to Q.5.
The following diagram displays a chemical reaction. Observe carefully and answer any four questions from (1) to (5).
Q. 1. The type of chemical reaction that will take place is
(A) Photochemical decomposition
(B) Displacement reaction
(C) Reduction reaction
(D) Combination reaction
Ans. Option (A) is correct.
Explanation: The type of chemical reaction that will take place is photochemical decomposition. This is a type of decomposition kirim reaction which involves the use of light energy for decomposition.
Q. 2. What colour change is observed in silver chloride?
(A) Silver chloride turns white.
(B) Silver chloride turns brown.
(C) Silver chloride shows no colour change.
(D) White silver chloride changes to grey.
Ans. Option (A) is correct
Explanation: When silver chloride is exposed to sunlight, it decomposes to give silver metal and chlorine gas. In this reaction white color of silver chloride changes to grayish white due to the formation of silver metal.
Q. 3. The correct balanced chemical equation involves:
(A) 2AgCl (s) →sunlight 2Ag (s) + Cl₂ (g)
(B) Ag + Cl → AgCl
(C) AgCl₂ → Ag2 + Cl₂
(D) AgCl sunlight →→ 2Ag + Cl₂
Ans. Option (A) is correct.
Explanation: The decomposition reaction of silver chloride into silver and chlorine by light can be depicted as:
2AgCl(s) 2Ag(s) Sunlight+ Cl₂(g)
Q. 4. When decomposition is carried out by heating, it is called as:
(A) Heat decomposition
(B) Photolytic decomposition
(C) Electrolytic decomposition
(D) Thermal decomposition Ans. Option
(D) is correct.
Explanation: Thermal decomposition reaction uses the energy in the form of heat. For example.
Calcium carbonate on heating decomposes to give calcium oxide and carbon dioxide.
CaCO3(s) Heat CaO(s) + CO,(g)
CaCO3(s) Heat CaO(s) + CO,(g)
(Limestone) (Quick lime)
#########
and
Q. 3. The correct balanced chemical equation involves:
(A) 2AgCl (s) sunlight → 2Ag (s) + Cl₂ (g)
(B) Ag + Cl → AgCl
(C) AgCl₂ → Ag2 + Cl₂
(D) AgCl sunlight, 2Ag + Cl₂
Ans. Option (A) is correct.
Explanation: The decomposition reaction of silver chloride into silver and chlorine by light can be depicted as: Sunlight
2AgCl (s) sunlight → 2Ag (s) + Cl₂ (g)
Q. 5. The other silver salt which behaves like silver chloride in sunlight is:
(A) silver hydride
(B) silver bromide
(C) silver iodide
(D) silver nitrite
Ans. Option (B) is correct.
Explanation: silver bromide gives silver metal and bromine gas on photolytic decomposition. Decomposition reactions of silver chloride and silver bromide in presence of sunlight are used in black and white photography.
Explanation: silver bromide gives silver metal and bromine gas on photolytic decomposition. Decomposition reactions of silver chloride and silver bromide in presence of sunlight are used in black and white photography. 2AgCl(s)- →2Ag(s) + Cl₂(g)
2AgBr- → 2Ag + Br₂
Science Mcq Class 10 ACIDS, BASES and SALTS
STAND ALONE MCQs
Q. 1. An aqueous solution 'A' turns phenolphthalein solution pink. On addition of an aqueous solution 'B' to 'A', the pink colour disappears. The following statement is true for solution 'A' and 'B'.
(A) A is strongly basic and B is a weak base.
(B) A is acidic and B is a weak acid.
(C) A has pH greater than 7 and B has pH less than 7.
(D) A has pH less than 7 and B has pH greater than 7.
Ans. Option (C) is correct.
2. Identify the basic salt from the following salts:
(A) Na₂CO3
(B) NHẠCI
(D) KCI
(C) NaNO3
Ans. Option (A) is correct.
[Board SQP, 2020]
Explanation: Na₂CO3 is a basic salt.
Q. 3. Which one of the following can be used as an acid base indicator by a visually impaired student?
(A) Litmus
(B) Turmeric
(C) Vanilla essence
(D) Petunia leaves
Ans. Option (C) is correct.
Explanation: Vanilla essence can be used as an acid-base indicator by visually impaired students as it is an olfactory indicator whose odour changes in acidic or basic media.
AI Q. 4. Which of the following is acidic in nature?
(A) Lime juice
(C) Lime water
(B) Human blood
(D) Antacid
Ans. Option (A) is correct.
Explanation: Lime juice is acidic in nature as the juice is obtained from lime, a citrus fruit. This contains citric acid, and is therefore sour in taste.
Q. 5. During the preparation of hydrogen chloride gas on a humid day, the gas is usually passed through the guard tube containing calcium chloride. The role of calcium chloride taken in the guard tube is to
(A) absorb the evolved gas.
(B) moisten the gas.
(C) absorb moisture from the gas.
(D) absorb C ions from the evolved gas.
Ans. Option (C) is correct.
Explanation: The role of calcium chloride taken
in the guard tube is to absorb moisture from
the gas. This is because calcium chloride is used
as a drying agent which absorbs moisture from the hydrogen chloride (HCI) gas.
Q. 6. Which of the following are present in a dilute aqueous solution of hydrochloric acid?
(A) H3O+ + Cl-
(B) H3O+ + OH
(C) CI-+ OH-
(D) Unionized HCI
Ans. Option (A) is correct.
Explanation: In a dilute aqueous solution of hydrochloric acid, H3O+ + Cl- ions are present.
7. What happens when a solution of an acid with a solution of a base in a test tube?
(i) The temperature of the solution increases (ii) The temperature of the solution decreases
(iii) The temperature of the solution remains the
same
(iv) Salt formation takes place
(A) (i) only
(B) (i) and (iii)
(C) (ii) and (iii) (D) (i) and (iv)
Ans. Option (D) is correct.
Explanation: When a solution of acid is mixed
is temperature of the solution increases and salt formation takes place. This is because the process is exothermic that is excess heat is produced by the acid-base reaction which is the net result of the processes of bond-breaking and bond-making.
Q. 8. Which of the following is used for dissolution of gold?
(A) Hydrochloric acid (B) Sulphuric acid
(C) Nitric acid
(D) Aqua regia
Ans. Option (D) is correct.
Explanation: Aqua Regia is a mixture of
concentrated HNO3 and concentrated HCI. Concentrated HNO3 acts as a very strong oxidising agent which ionises Au atoms and Concentrated HCl produces nascent chlorine which in turn reacts with ionised Au atoms thus forming auric chloride.
Q. 9. Which of the following salts does not con of crystallisation?
(A) Blue vitriol
(C) Washing soda
(B) Baking soda
(D) Gypsum
Ans. Option (B) is correct.
Explanation: Water of crystallisation fixed number of water molecules pres one formula unit of a salt. Potassium r barium sulphate, potassium chloride, s nitrate, baking soda, etc., are the salts t not contain water of crystallisation.
Q. 10. Sodium carbonate is a basic salt becaus salt of
(A) strong acid and strong base.
(B) weak acid and weak base.
(C) strong acid and weak base.
(D) weak acid and strong base.
Ans. Option (D) is correct.
Explanation: Sodium carbonate is a basic sa weak acid i.e. carbonic acid and a strong i.e. sodium hydroxide.
Q. 11. Common salt besides being used in kitche also be used as the raw material for making
(i) washing soda.
(ii) bleaching powde
(iii) baking soda.
(iv) slaked lime.
(A) (i) and (ii)
(B) (i), (ii) and (iv)
(C) (i) and (iii)
(D) (i), (iii) and (iv)
Ans. Option (C) is correct
Explanation: The common salt obtained is an important raw material for various materials of daily use, such as sodium hydroxide, baking soda, washing soda and many more.
Q. 12.One of the constituents of baking powder is sodium hydrogen carbonate, the other constituent is
(A) hydrochloric acid.
(B) tartaric acid.
(C) acetic acid.
(D) sulphuric acid.
Ans. Option (B) is correct.
Explanation: Baking powder is a mixture of baking soda (sodium hydrogen carbonate) and a mild edible acid such as tartaric acid.
Q. 13. Which of the following is not a salt?
(A) Sodium chloride
(B) Slaked lime
(C) Lead sulphide
(D) Zinc nitrate
Ans. Option (B) is correct.
Explanation: Slaked lime or Ca(OH)₂ is not a salt.
Q. 14. A compound is prepared from gypsum upon heating to a temperature of 373 K and it changes back to gypsum on adding water. Which is the incorrect statement about the compound?
(A) The compound is used for setting fractured bones.
(B) The compound is called plaster of Paris which is calcium sulphate dehydrate with a formula
CaSO4.2HO.
(C) If heated at higher temperature, the compound becomes dehydrated and is called dead burnt plaster.
(D) Both (A) and (B).
Ans. Option (B) is correct.
Explanation: The compound is called plaster of Paris which is calcium sulphate hemihydrate with a formula CaSO4.1/2H₂O.
Q. 15. A milk man adds a very small amount of baking soda to fresh milk. Why?
(A) To increase the rate of fermentation
(B) To decrease the rate of fermentation
(C) To increase its quality
(D) To make paneer
Ans. Option (B) is correct.
Explanation: A milk man adds a very small amount of baking soda to fresh milk to decrease the rate of fermentation.
Q. 16. Which of the given substances is used in the following applications?
I. It is used as a fire proofing material.
II. It is used for sealing gaps in laboratory apparatus.
III. It is used in making toys.
(A) Bleaching powder
(B) Plaster of Paris
(C) Baking soda
(D) Washing soda
Ans. Option (B) is correct.
Explanation: The chemical formula for Plaster of paris is (Ca(SO4).2H₂O) which is commonly used as fire proofing insulating material on walls, for casting toys and can be used in sealing pots and lab apparatus.
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