SCIENCE- Class X
Sample Case Studies
1. Read the following and answer any four questions from 1.1 to 1.5:
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.
1.1 The substance not likely to contain CaCO3 is
a) Dolomite
b) A marble statue
c) Calcined gypsum
d) Sea shells.
1.2 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 mins 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
1.3 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
b) Photosynthesis
c) Transpiration
d) sphotolysis
1
, 1.4 Marble statues are corroded or stained when they repeatedly come into contact with polluted
rain water. Identify the main reason.
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
hence it reacts with calciumcarbonate
d) calcium carbonate dissolves in water to give calcium hydroxide.
1.5 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
b) sodium oxide
c) calcium
d) calcium oxide
Answer 1.1 white precipitate is obtained
Key 1.2 0-5 min
1.3 photosynthesis
1.4 polluted water is acidic in nature hence it reacts with calcium carbonate
1.5 calcium oxide
******
2. Read the following and answer any four questions from 2.1 to 2.5:
The reaction between MnO2 with HCl is depicted in the following diagram. It was observed that
a gas with bleaching abilities was released .
2.1 The chemical reaction between MnO2 and HCl is an example of:
a) displacement reaction
b) combination reaction
c) redox reaction
d) decomposition
ecomposition reaction.
2.2 Chlorine gas reacts with _______ to form bleaching powder.
a) dry Ca(OH)2
b) dil. solution of Ca(OH)2
c) conc. solution of Ca(OH)2
d) dry CaO
2
, 2.3 Identify the correct statement from the following:
MnO2 is getting reduced whereas HCl is getting oxidized
a) MnO2 is getting oxidized whereas HCl is getting reduced.
b) MnO2 and HCl both are getting reduced.
c) MnO2 and HCl both are getting oxidized.
2.4 In the above discussed reaction, what is the nature of MnO2 ?
a) Acidic oxide
b) Basic oxide
c) Neutral oxide
d) Amphoteric oxide
2.5 What will happen if we take dry HCl gas instead of aqueous solution of HCl?
a) Reaction will occur faster.
b) Reaction will not occur.
c) Reaction rate will be slow
d) Reaction rate will remain the same.
2.1(c) redox reaction
Answer 2.2(a) dry Ca(OH)2
Key 2.3(a)MnO2 is getting reduced whereas HCl is getting oxidized
2.4(b) Basic oxide
2.5(b) Reaction will not occur
*******
3. Read the following and answer any four questions from 3.1 to 3.5:
Chemistry in Automobiles:
Foran internalcombustion enginetomoveavehicledowntheroad,itmustconvertthe 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 reactiondepictingcomplete combustionof
gasolineinfullsupplyof air:
3.1 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 H2 O
d) CO2 H2 O
3.2 Identify the types of chemical reaction occurring during the combustion of fuel:
a) Oxidation & Endothermic reaction
b) Decomposition & Exothermic reaction
c) Oxidation & Exothermic reaction
d) Combination & Endothermic reaction
3
Sample Case Studies
1. Read the following and answer any four questions from 1.1 to 1.5:
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.
1.1 The substance not likely to contain CaCO3 is
a) Dolomite
b) A marble statue
c) Calcined gypsum
d) Sea shells.
1.2 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 mins 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
1.3 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
b) Photosynthesis
c) Transpiration
d) sphotolysis
1
, 1.4 Marble statues are corroded or stained when they repeatedly come into contact with polluted
rain water. Identify the main reason.
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
hence it reacts with calciumcarbonate
d) calcium carbonate dissolves in water to give calcium hydroxide.
1.5 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
b) sodium oxide
c) calcium
d) calcium oxide
Answer 1.1 white precipitate is obtained
Key 1.2 0-5 min
1.3 photosynthesis
1.4 polluted water is acidic in nature hence it reacts with calcium carbonate
1.5 calcium oxide
******
2. Read the following and answer any four questions from 2.1 to 2.5:
The reaction between MnO2 with HCl is depicted in the following diagram. It was observed that
a gas with bleaching abilities was released .
2.1 The chemical reaction between MnO2 and HCl is an example of:
a) displacement reaction
b) combination reaction
c) redox reaction
d) decomposition
ecomposition reaction.
2.2 Chlorine gas reacts with _______ to form bleaching powder.
a) dry Ca(OH)2
b) dil. solution of Ca(OH)2
c) conc. solution of Ca(OH)2
d) dry CaO
2
, 2.3 Identify the correct statement from the following:
MnO2 is getting reduced whereas HCl is getting oxidized
a) MnO2 is getting oxidized whereas HCl is getting reduced.
b) MnO2 and HCl both are getting reduced.
c) MnO2 and HCl both are getting oxidized.
2.4 In the above discussed reaction, what is the nature of MnO2 ?
a) Acidic oxide
b) Basic oxide
c) Neutral oxide
d) Amphoteric oxide
2.5 What will happen if we take dry HCl gas instead of aqueous solution of HCl?
a) Reaction will occur faster.
b) Reaction will not occur.
c) Reaction rate will be slow
d) Reaction rate will remain the same.
2.1(c) redox reaction
Answer 2.2(a) dry Ca(OH)2
Key 2.3(a)MnO2 is getting reduced whereas HCl is getting oxidized
2.4(b) Basic oxide
2.5(b) Reaction will not occur
*******
3. Read the following and answer any four questions from 3.1 to 3.5:
Chemistry in Automobiles:
Foran internalcombustion enginetomoveavehicledowntheroad,itmustconvertthe 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 reactiondepictingcomplete combustionof
gasolineinfullsupplyof air:
3.1 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 H2 O
d) CO2 H2 O
3.2 Identify the types of chemical reaction occurring during the combustion of fuel:
a) Oxidation & Endothermic reaction
b) Decomposition & Exothermic reaction
c) Oxidation & Exothermic reaction
d) Combination & Endothermic reaction
3
