List of top Questions asked in JEE Main- 2021

If the solution curve of the differential equation \((2x - 10y^3)dy + y dx = 0\), passes through the points (0, 1) and (2, \(\beta\)), then \(\beta\) is a root of the equation :
Two poles, AB of length a metres and CD of length a + b (b \(\neq\) a) metres are erected at the same horizontal level with bases at B and D. If BD = x and \(\tan(\angle ACB) = \frac{1}{2}\), then :

Let $f:(-\frac{\pi}{4}, \frac{\pi}{4}) \rightarrow R$ be defined as 

If f is continuous at $x=0$, then the value of $6a+b^2$ is equal to : 
 

\( \lim_{x \to 0} \frac{\sin^2(\pi \cos^4 x)}{x^4} \) is equal to :
The domain of the function \(f(x) = \sin^{-1} \left( \frac{3x^2 + x - 1}{(x - 1)^2} \right) + \cos^{-1} \left( \frac{x - 1}{x + 1} \right)\) is :
If for $x, y \in \mathbb{R}, x>0, y = \log_{10} x + \log_{10} x^{1/3} + \log_{10} x^{1/9} + \dots$ upto $\infty$ terms and $\frac{2 + 4 + 6 + \dots + 2y}{3 + 6 + 9 + \dots + 3y} = \frac{4}{\log_{10} x}$, then the ordered pair $(x, y)$ is equal to :

The major product of the following reaction is : 

The correct sequential addition of reagents in the preparation of 3-nitrobenzoic acid from benzene is :
Match List - I with List - II :
List - I (a) Antifertility drug (b) Antibiotic (c) Tranquilizer (d) Artificial Sweetener
List - II (i) Meprobamate (ii) Alitame (iii) Norethindrone (iv) Salvarsan Choose the most appropriate match :
Hydrolysis of sucrose gives :


Consider the following reaction, the major product 'P' is: 

The correct structures of A and B formed in the following reactions are : 

 

In the following sequence of reactions, the final product D is : 

 

In polymer Buna-S : 'S' stands for :
Which of the following ore is concentrated using group 1 cyanide salt ?
Which one of the following carbonyl compounds cannot be prepared by addition of water on an alkyne in the presence of HgSO₄ and H₂SO₄ ?
Given below are two statements:
Statement I: The pH of rain water is normally ~5.6.
Statement II: If the pH of rain water drops below 5.6, it is called acid rain.
The ionic radii of $K^+$, $Na^+$, $Al^{3+}$ and $Mg^{2+}$ are in the order :
Assertion A : Hydrogen is the most abundant element in the Universe, but it is not the most abundant gas in the troposphere. Reason R : Hydrogen is the lightest element.
Which one of the following when dissolved in water gives coloured solution in nitrogen atmosphere ?
Match List - I with List - II : List - I (Chemicals)
(a) Alcoholic potassium hydroxide
(b) Pd/BaSO₄
(c) BHC (Benzene hexachloride)
(d) Polyacetylene List - II (Use/Preparation/Constituent)
(i) electrodes in batteries
(ii) obtained by addition reaction
(iii) used for β-elimination reaction
(iv) Lindlar's Catalyst
Which of the following are isostructural pairs ? (Note: Based on typical JEE pairs like $SO_4^{2-}$ and $BF_4^-$ or $NH_3$ and $PH_3$)

What is the final product (major) 'A' in the given reaction ? $CH_3 - CH = CH - CH_3 \xrightarrow{HCl} A$ 

Chalcogen group elements are :
The oxide that gives H\(_2\)O\(_2\) most readily on treatment with H\(_2\)O is :