JEE Main 2020 Answer Key (Released), Papers, Shift 1 & 2 – Check Here

Paper:1

Shift 1 (Chemistry):

Q.1) Among the following statements that which was not proposed by Dalton was:

(a) Matter consists of invisible atoms

(b) When gases combine or reproduced in a chemical reaction they do so in a simple ratio by volume provided all gases are at the same T and P.

(c) Chemical reactions involve the reorganization of atoms. These are neither created nor destroyed in a chemical reaction

Answer: Option (b) is correct as it was proposed by Gay Lussac’s law of gaseous volume.

Therefore, Option(b) is correct.

Q.2) Which theory explains completely about bonding in coordination compounds?

Answer: Valence bond theory

Q.3) Which among following is the purest form of iron:

1. Cast iron
2. Wrought iron
3. Pig iron
4. None of these

Answer: Option II. Wrought iron

Q.4) The atomic radius of Ag is closest to:
(a) Ni
(b) Cu
(c) Au
(d) Hg

Answer: The atomic radius of Ag is closest to Hg.

Therefore, Option (d) is correct.

Q.5) The relative strength of interionic/intermolecular forces in decreasing order is:

(a) Ion-dipole > dipole-dipole > Ion-ion
(b) dipole-dipole > ion-dipole > ion-ion
(c) ion-ion > ion-dipole > dipole-dipole
(d) ion-dipole > ion-ion > dipole-dipole

Answer: The correct order of intermolecular forces is:

Ion-ion > ion-dipole > dipole-dipole

Therefore, Option(c) is correct.

Q.6) The increasing order of pKb for the following compounds will be:

(a) NH2-CH=NH
(b) Image
(c) CH3NHCH3

Answer:

Thus, the increasing order of basicity is: 
(a) > (b) > (c)

Q.7) Match the following:

(i) Riboflavin                          (a) Beriberi
(ii) Thiamine                           (b) Scurvy
(iii) Pyridoxine                        (c) Cheilosis
(iv) Ascorbic acid                    (d) Convulsions

Answer:
  (i) Riboflavin              –          (c) Cheilosis
(ii) Thiamine              –          (a) Beriberi
(iii) Pyridoxine           –          (d) Convulsions
(iv) Ascorbic acid       –          (b) Scurvy

Q.8) The oxidation number of potassium in K₂O , K₂O₂ and KO2, respectively is :

Answer:

For K₂O: 2x – 2 = 0
x = 1

For K₂O₂: 2x – 4 = 0
x = 2 

For KO₂: x – 4 = 0
x = 4

Q.9) The number of orbitals associated with quantum numbers n = 5, m_s = +1/2 is:

Answer:

We have:

n – 5, m_s = +1/2

Thus, values of l are from 0 to (n-1)

l = 0 to 4

Thus, values of l are 5s, 5p, 5d, 5f and 5g

Now, the total number of orbitals = n² = 5² = 25

Q.10) At 35^oC, the vapour pressure of CS₂ is 512mm Hg and that of acetone is 344mm Hg. A solution of CS₂ in acetone has a total vapour pressure of 600mm Hg. The false statement among the following is:
(a) CS₂ and acetone are less attracted to each other than to themselves.
(b) Heat must be absorbed in order to produce the solution at 35^oC.
(c) Raoult’s law is not obeyed by this system.
(d) A mixture of 100ml CS₂ and 100ml acetone has a volume of <200ml.

Answer:

We have:

P_observed = 600Hg

We know:

P_calc = P^o_Ax_A + P^o_Bx_B
= 512x + 344 – 344x
= 168x + 344
= 512 ( if x =1 for miximum value)

Thus, P_calc < P_observed
Thus, the process is deviated from Raoult’s law, showing positive deviation from Raoult’s law.

\: 0}” v:shapes=”Picture_x0020_12″>, i.e, heat absorbed

Therefore, Option(d) is correct.

Q.11) In comparison to the zeolite process for the removal of permanent hardness, the synthetic resins method is:

(a) Less efficient as it exchanges only anions
(b) More efficient as it can exchange only cations.
(c) Less efficient as the resins cannot be generated
(d) More efficient as it can exchange both cations and anions

Answer:

The synthetic resins method is more efficient as it can exchange both cations and anions.

Therefore, Option(d) is correct.

Mathematics:

Q.1) If the variance of first n natural number is 10 & variance of first m even natural number is 16, then the value of m+n is:

Answer: 18

Q.2) If 49^k +1 is a factor of 49¹²⁵ + 49¹²⁴+…..49+1, then find K

Answer: 63

Q.4) How many six-digit numbers can be formed using digit 1, 3, 5, 7, 9 such that in each number each digit should be used at least once.

Answer: 1800

Q.5) Sum of 5 no. in AP is 25 & their product is 2520, if one of them is -1/2 then finds the largest number?

Answer: 16

Q.6) If linear equation,

2x + 2ay + az= 0

2x + 3by + bz= 0

2x + 4cy + cz= 0

where a, b, c  R are non-zero & are distinct, has non-zero solutions then

1. 1/a, 1/b, 1/c are in A.P
2. a, b, c in AP
3. a, b, c are in CP
4. a+b+c= 0

Answer: Option 1

Q.7) The total no. of 6 digit number that can be formed using all the digits 1, 3, 5, 7, 9 only is?

Answer: 1800