List of top Questions asked in JEE Main- 2021

Assume a cell with the following reaction

\(\mathrm{Cu_{(s)} + 2Ag^{+}(1\times 10^{-3}\,M) \rightarrow Cu^{2+}(0.250\,M) + 2Ag_{(s)}}\)

\(E^{\Theta}_{cell} = 2.97\) V

\(E_{cell}\) for the above reaction is ______________ V. (Nearest integer)

[Given : log 2.5 = 0.3979, T = 298 K]
Sulphide ion is soft base and its ores are common for metals.
(a) Pb (b) Al (c) Ag (d) Mg
Value of \(K_P\) for the equilibrium reaction

\(\mathrm{N_2O_{4(g)} \rightleftharpoons 2NO_{2(g)}}\) at 288 K is 47.9. The \(K_C\) for this reaction at same temperature is ____________. (Nearest integer)

(R = 0.083 L bar \(\mathrm{K^{-1}\,mol^{-1}}\))
The total number of unpaired electrons present in \(\mathrm{[Co(NH_3)_6]Cl_2}\) and \(\mathrm{[Co(NH_3)_6]Cl_3}\) is :
The number of acyclic structural isomers (including geometrical isomers) for pentene are ___________
Match List-I with List-II
List-I (Elements)List-II (Properties)
(a) Ba(i) Organic solvent soluble compounds
(b) Ca(ii) Outer electronic configuration \(6s^2\)
(c) Li(iii) Oxalate insoluble in water
(d) Na(iv) Formation of very strong monoacidic base

Choose the correct answer from the options given below :
Which one of the following 0.06 M aqueous solutions has lowest freezing point?
Given below are the statements about diborane
(a) Diborane is prepared by the oxidation of \(\mathrm{NaBH_4}\) with \(\mathrm{I_2}\)
(b) Each boron atom is in \(sp^2\) hybridized state
(c) Diborane has one bridged 3 centre-2-electron bond
(d) Diborane is a planar molecule
The option with correct statements is :
The water having more dissolved \(\mathrm{O_2}\) is :
Match List-I with List-II :
List-IList-II
(a) Chloroprene(i), (ii), (iii): structures as shown in the figure
(b) Neoprene
(c) Acrylonitrile(iv) \(\mathrm{CH_2=CH-CN}\)
(d) Isoprene


Choose the correct answer from the options given below :
The set having ions which are coloured and paramagnetic both is :
Which one of the following group-15 hydride is the strongest reducing agent?
Thiamine and pyridoxine are also known respectively as :
An organic compound A (\(\mathrm{C_6H_6O}\)) gives dark green colouration with ferric chloride. On treatment with \(\mathrm{CHCl_3}\) and KOH, followed by acidification gives compound B. Compound B can also be obtained from compound C on reaction with pyridinium chlorochromate (PCC). Identify A, B and C.
Which one of the following reactions does not occur?
Which of the following molecules does not show stereo isomerism?
Which of the following compounds will provide a tertiary alcohol on reaction with excess of \(\mathrm{CH_3MgBr}\) followed by hydrolysis?
Match List-I with List-II :
List-I (Species)List-II (Hybrid Orbitals)
(a) \(SF_4\)(i) \(sp^3d^2\)
(b) \(IF_5\)(ii) \(d^2sp^3\)
(c) \(NO_2^+\)(iii) \(sp^3d\)
(d) \(NH_4^+\)(iv) \(sp^3\)
(v) \(sp\)

Choose the correct answer from the options given below :
Which of the following compounds does not exhibit resonance?

In the chemical reactions given above A and B respectively are :
Isotope(s) of hydrogen which emits low energy \(\beta^-\) particles with \(t_{1/2}\) value \(\gt\) 12 years is/are
Which one of the following statements for D.I. Mendeleeff, is incorrect?
Which purification technique is used for high boiling organic liquid compound (decomposes near its boiling point)?
In 5 minutes, a body cools from \(75^\circ\mathrm{C}\) to \(65^\circ\mathrm{C}\) at room temperature of \(25^\circ\mathrm{C}\). The temperature of body at the end of next 5 minutes is ________ \(^\circ\mathrm{C}\).
In an electric circuit, a cell of certain emf provides a potential difference of 1.25 V across a load resistance of \(5\ \Omega\). However, it provides a potential difference of 1 V across a load resistance of \(2\ \Omega\). The emf of the cell is given by \(\dfrac{x}{10}\) V. Then the value of x is ________.