1

JEE Main 2019 (Online) 11th January Evening Slot

The radius of the largest sphere which fits properly at the centre of the edge of a body centred cubic unit cell is : (Edge length is represented by 'a')
A
0.134 a
B
0.067 a
C
0.047 a
D
0.027 a

Explanation

a = 2(R + r)

$\Rightarrow$ ${a \over 2} = \left( {R + r} \right)$ ......(1)

For bcc, $\sqrt 3 a$ = 4R

Using (i) and (ii)

${a \over 2} = \left( {{{a\sqrt 3 } \over 4} + r} \right)$

$\Rightarrow$ r = $a\left( {{{2 - \sqrt 3 } \over 4}} \right)$

$\Rightarrow$ r = 0.067 a
2

JEE Main 2019 (Online) 11th January Evening Slot

Among the colloids cheese (C), milk (M), and smoke (S), the correct combination of the dispersed phase and dispersion medium, respectively is :
A
C : liquid in solid ; M : liquid in liquid ; S : solid in gas
B
C : liquid in solid ; M : liquid in solid ; S : solid in gas
C
C : solid in liquid ; M : liquid in liquid ; S : gas in solid
D
C : solid in liqid ; M : solid in liquid ; S : solid in gas

Explanation

Cheese (C) is liquid dispersed in solid.

Milk (M) is liquid dispersed in liquid.

Smoke (S) is solid dispersed in gas.
3

JEE Main 2019 (Online) 12th January Morning Slot

Given
Gas H2 CH4 CO2 SO2
Critical
Temperature / K
33 190 304 630

On the basis of data given above, predict which of the following gases shows least adsorption on a definite amount of charcoal ?
A
SO2
B
CH4
C
H2
D
CO2

Explanation

Adsorption $\propto$ Tc

Therefore, H2 gas shows least adsorption on a definite amount of charcoal.
4

JEE Main 2019 (Online) 12th January Evening Slot

Among the following the false statement is -
A
Lyophilic sol can be coagulated by adding an electrote
B
Tyndall effect can be used to distinguish between a colloidal solution and a true solution
C
It is possible to cause artificial rain by throwing electrified sand carrying charge opposite to the one on clouds from an aeroplane
D
Latex is a colloidal solution of rubber particles which are positively charged

Explanation

Latex is a colloidal solution of rubber particles which are negatively charged.