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1

### JEE Main 2021 (Online) 27th August Morning Shift

The number of water molecules in gypsum, dead burnt plaster and plaster of Paris, respectively are :
A
2, 0 and 1
B
0.5, 0 and 2
C
5, 0 and 0.5
D
2, 0 and 0.5

## Explanation

Gypsum $$CaS{O_4}.2{H_2}O$$
Plaster of Paris $$CaS{O_4}.{1 \over 2}{H_2}O$$
Dead burnt plaster $$CaS{O_4}$$
2

### JEE Main 2021 (Online) 26th August Morning Shift

What are the products formed in sequence when excess of CO2 is passed in slaked lime?
A
Ca(HCO3)2, CaCO3
B
CaCO3, Ca(HCO3)2
C
CaO, Ca(HCO3)2
D
CaO, CaCO3

## Explanation

$$Ca{(OH)_2} + C{O_2} \to CaC{O_3} \downarrow + {H_2}O$$

$$CaC{O_3} \downarrow + C{O_2} + {H_2}O \to Ca{(HC{O_3})_2}$$
3

### JEE Main 2021 (Online) 27th July Evening Shift

Match List - I with List - II :

List - I List - II
(a) Li (i) photoelectric cell
(b) Na (ii) absorbent of $$C{O_2}$$
(c) K (iii) coolant in fast breeder nuclear reactor
(d) Cs (iv) treatment of cancer
(v) bearings for motor engines

Choose the correct answer from the options given below :
A
(a) - (v), (b) - (i), (c) - (ii), (d) - (iv)
B
(a) - (v), (b) - (ii), (c) - (iv), (d) - (i)
C
(a) - (iv), (b) - (iii), (c) - (i), (d) - (ii)
D
(a) - (v), (b) - (iii), (c) - (ii), (d) - (i)

## Explanation

Li makes alloy with Lead to make white metal bearings for motor engines

Liquid Na metal is used s coolant in fast breeder nuclear reactor

K is a very absorbent of CO2

Cs is used in making photoelectric cell
4

### JEE Main 2021 (Online) 27th July Morning Shift

Given below are two statements : One is labelled as Assertion A and the other labelled as Reason R.

Assertion A : Lithium halides are some what covalent in nature.

Reason R : Lithium posses high polarisation capability.

In the light of the above statements, choose the most appropriate answer from the options given below :
A
A is true but R is false
B
A is false but R is true
C
Both A and R are true but R is NOT the correct explanation of A
D
Both A and R are true and R is the correct explanation of A

## Explanation

Lithium due to small size has very high polarization capability and thus increases covalent nature of Halides.

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