Practice problems on JEE Mains, JEE Mains 2021 Aug 26 Shift 1

Question 1

What the products formed in sequence when excess of CO2​ is passed in slaked lime?

Accepted Answer

CaCO3​,Ca(HCO3​)2​

Answer

Ca(HCO3​)2​,CaCO3​

Answer

CaO,Ca(HCO3​)2​

Answer

CaO,CaCO3​

Question 2

Which one of the following methods is most suitable for preparing deionized water ?

Accepted Answer

Synthetic resin method

Answer

Permutit method

Answer

Calgon’s method

Answer

Clark’s method

Question 3

Let A and B be independent events such that P(A) = p, P(B) = 2p, The largest value of p, for which P (exactly one of A, B occurs) =95​ is:

Accepted Answer

125​

Answer

31​

Answer

94​

Answer

92​

Question 4

Statement-I : By doping semiconductor with pentavalent material, the density increases.Statement-II: The n-type semiconductor has net negative charge.In the light of the above statements, choose the most appropriate answer from the options given below:

Accepted Answer

Statement I is true but Statement II is false

Answer

Both Statement I and Statement II are false

Answer

Both Statement I and Statement II are true

Answer

Statement I is false but Statement II is true

Question 5

Among the following compounds I-IV, which one forms a yellow precipitate on reacting sequentially with (i) NaOH (ii) dil.HNO3​ (iii) AgNO3​ ?

Accepted Answer

IV

Answer

I

Answer

III

Answer

II

Question 6

The polymer formed on heating Novolac with formaldehyde is :

Accepted Answer

Bakelite

Answer

Polyester

Answer

Melamine

Answer

Nylon 6, 6

Question 7

Out of all the patients in a hospital 89% are found to be suffering from heart ailment and 98% are suffering from lungs infection. If K% of them are suffering from both ailments, then K can not belong to the set :

Accepted Answer

{79, 81, 83, 85}

Answer

{80, 83, 86, 89}

Answer

{84, 87, 90, 93}

Answer

{84, 86, 88, 90}

Question 8

In a Screw Gauge, fifth division of the circular scale coincides with the reference line when the ratchet is closed. There are 50 divisions on the circular scale, and the main scale moves by 0.5 mm on a complete rotation. For a particular observation the reading on the main scale is 5 mm and the 20th division of the circular scale coincides with reference line. Calculate the true reading.

Accepted Answer

5.15 mm

Answer

5.00 mm

Answer

5.20 mm

Answer

5.25 mm

Question 9

The incorrect statement is :

Accepted Answer

Cl2​ is more reactive than CIF

Answer

On hydrolysis CIF forms HOCl and HF

Answer

F2​ is more reactive than CIF.

Answer

F2​ is a stronger oxidizing agent than Cl2 in aqueous solution.

Question 10

The conversion of hydroxyapatite occurs due to presence of F− in water. The correct formula of hydroxyapatite is:

Accepted Answer

[3Ca3​(PO4​)2​Ca(OH)2​]

Answer

[3Ca3​(PO4​)2​⋅CaF2​]

Answer

[3Ca(OH)2​CaF2​]

Answer

[Ca3​(PO4​)2​⋅CaF2​]

Question 11

Inside a uniform spherical shell:(a) The gravitation field is zero(b) The gravitational potential is zero(c) The gravitational field is same everywhere(d) the gravitational potential is same everywhere(e) all of the aboveChoose the most appropriate answer from the options given below:

Accepted Answer

(a), (c) and (d) only

Answer

(b), (c), and (d) only

Answer

(e) only

Answer

(a), (b) and (c) only

Question 12

If the sum of an infinite GP a,ar,ar2,ar3, . is 15 and the sum of the squares its each term is 150 , then the sum of ar2,ar4,ar6,…….. is :

Accepted Answer

21​

Answer

225​

Answer

29​

Answer

25​

Question 13

Given below are two statements :Statement-I : Frenkel defects are vacancy as well as interstitial defects.Statement-II : Frenkel defect leads to colour in ionic solids due to presence of F-centres.Choose the most appropriate answer for the statements from the options given below :

Accepted Answer

Statement-I is true but Statement-II is false

Answer

Both Statement-I and Statement-II are false

Answer

Statement-I is false but Statement-II is true

Answer

Both Statement-I and Statement-II are true