List of top Questions asked in JEE Main- 2021

The hybridization and magnetic nature of [Mn(CN)$_6$]$^{4-}$ and [Fe(CN)$_6$]$^{3-}$, respectively are :
Given below are two statements : Statement I : An allotrope of oxygen is an important intermediate in the formation of reducing smog. Statement II : Gases such as oxides of nitrogen and sulphur present in troposphere contribute to the formation of photochemical smog. In the light of the above statements, choose the correct answer from the options given below :
Complete combustion of 1.80 g of an oxygen containing compound (C$_x$H$_y$O$_z$) gave 2.64 g of CO$_2$ and 1.08 g of H$_2$O. The percentage of oxygen in the organic compound is :

Identify A in the given chemical reaction. CH$_2$=CH-CH(CH$_3$)-CH$_3$ $\xrightarrow{Mo_2O_3, 773 K, 10-20 atm}$ A (major product)

Identify A and B in the chemical reaction. p-Nitrotoluene $\xrightarrow{Cl_2, h\nu}$ A $\xrightarrow{NaI, dry acetone}$ B

The major product of the following chemical reaction is : R-CN $\xrightarrow{(1) H_3O^+, \Delta (2) SOCl_2 (3) Pd/BaSO_4, H_2}$ ? (Using $R$ as the alkyl group from the prompt skeleton)
Which one of the following reactions will not form acetaldehyde ?

Compound(s) which will liberate carbon dioxide with sodium bicarbonate ($NaHCO_3$) solution is/are : A = Urea, B = Benzoic acid, C = p-Nitrophenol

Which of the following reaction/s will not give p-aminoazobenzene ? 

Which statement is correct ?
Which of the glycosidic linkage between galactose and glucose is present in lactose ?
0.4 g mixture of NaOH, Na$_2$CO$_3$ and some inert impurities was first titrated with N/10 HCl using phenolphthalein as an indicator, 17.5 mL of HCl was required at the end point. After this methyl orange was added and titrated. 1.5 mL of same HCl was required for the next end point. The weight percentage of Na$_2$CO$_3$ in the mixture is _________
A car tyre is filled with nitrogen gas at 35 psi at 27$^\circ$C. It will burst if pressure exceeds 40 psi. The temperature in $^\circ$C at which the car tyre will burst is ___________
The reaction of cyanamide, NH$_2$CN(s), with oxygen was run in a bomb calorimeter and $\Delta U$ was found to be -742.24 kJ mol$^{-1}$. The magnitude of $\Delta H_{298}$ for the reaction NH$_2$CN(s) + 3/2 O$_2$(g) $\rightarrow$ N$_2$(g) + CO$_2$(g) + H$_2$O(l) is _________ kJ.
1 molal aqueous solution of an electrolyte A$_3$B$_3$ is 60% ionised. The boiling point of the solution at 1 atm is __________ K. [Given $K_b$ (H$_2$O) = 0.52 K kg mol$^{-1}$, $T_b$ pure water = 373.15 K]
In basic medium CrO$_4^{2-}$ oxidises S$_2$O$_3^{2-}$ to form SO$_4^{2-}$ and itself changes into Cr(OH)$_4^-$. The volume of 0.154 M CrO$_4^{2-}$ required to react with 40 mL of 0.25 M S$_2$O$_3^{2-}$ is _________ mL.

For aA + bB $\rightarrow$ cC + dD, the plot of log k vs 1/T is given below :

The temperature at which the rate constant is $10^{-4}$ s$^{-1}$ is __________ K. [Rate constant is $10^{-5}$ s$^{-1}$ at 500 K.]

The ionization enthalpy of Na$^+$ formation is 495.8, electron gain enthalpy of Br is -325.0, and lattice enthalpy of NaBr is -728.4 kJ mol$^{-1}$. The energy for the formation of NaBr ionic solid is (-) __________ $\times 10^{-1}$ kJ mol$^{-1}$.
Among the following, the number of halide(s) which is/are inert to hydrolysis is ___________: (A) BF$_3$, (B) SiCl$_4$, (C) PCl$_5$, (D) SF$_6$
Consider the reaction: CH$\equiv$CH $\xrightarrow{\text{Red hot Fe}}$ (1) $\xrightarrow{CO, HCl, AlCl_3}$ (2). The number of sp$^2$ hybridized carbon atom(s) in the product is __________.

Using the provided information in paper chromatography

The calculated $R_f$ value of A is __________ $\times 10^{-1}$.

Let f,g : ℕ → ℕ such that f(n+1) = f(n) + f(1) ∀ n ∈ ℕ and g be any arbitrary function. Which of the following statements is NOT true?
Let the lines \( (2 - i)z = (2 + i)\bar{z} \) and \( (2 + i)z + (i - 2)\bar{z} - 4i = 0 \), (here \( i^2 = -1 \)) be normal to a circle \( C \). If the line \( iz + \bar{z} + 1 + i = 0 \) is tangent to this circle \( C \), then its radius is :
The integer k, for which the inequality x² - 2(3k-1)x + 8k² - 7>0 is valid for every x in ℝ, is :
If Rolle's theorem holds for the function f(x) = x³ - ax² + bx - 4, x ∈ [1, 2] with f'(4/3) = 0, then ordered pair (a, b) is equal to :