Case Studies Class 10

📝 Science (Case Studies) 

1. Read the following and answer 

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 `CaCO_3` is

a) Dolomite

b) A marble statue

c) Calcined gypsum

d) Seashells.

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 that occurs in the presence of sunlight. Identify the name of the process -

a) Respiration

b) Photosynthesis

c) Transpiration

d) photolysis

1.4 Marble statues are corroded or stained rainwater. 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.

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

Key

1.1 white precipitate is obtained

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 

The reaction between `MnO_2` with `HCl` is depicted in the following diagram. It was observed that gas with bleaching abilities was released.

2.1 The chemical reaction between `MnO_2` and `HCl` is an example of 

a) displacement reaction

b) combination reaction

c) redox reaction

d) decomposition 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`

2.3 Identify the correct statement from the following:

`MnO_2` is getting reduced whereas `HCl` is getting oxidized

a) `MnO_2` is getting oxidized whereas `HCl` is getting reduced.

b) `MnO_2` and `HCl` both are getting reduced.

c) `MnO_2` and `HCl` both are getting oxidized.

d) All 

2.4 In the above-discussed reaction, what is the nature of `MnO_2`?

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 the 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

Answer

Key

2.1 (c) redox reaction

2.2 (a) dry `Ca(OH)_2`

2.3 (a) `MnO_2` is getting reduced whereas `HCl` is getting oxidized

2.4 (b) Basic oxide

2.5 (b) Reaction will not occur

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