List of top Questions asked in JEE Main

An electrochemical cell, consist of the following two redox couples, \(M^{x+}(aq)/M(s) [E_{red}^\circ = +0.15 V]\) and \(Fe^{3+}(aq)/Fe(s) [E_{red}^\circ = -0.036 V]\). The cell EMF (\(E_{cell}\)) is recorded to be 0.2057 V. If the reaction quotient of the electrochemical cell is found to be \(10^{-z}\), then the value of x is _________. (Nearest integer)
[Given : M is a p-block metal and \(\frac{2.303 RT}{F} = 0.059 V\)]

Which of the following pictorial diagram most correctly represents the \( \pi^* \) (\( \pi \) - antibonding) molecular orbital between two atoms if the internuclear axis is taken to be in the z-direction ( \( \xrightarrow{\text{z-axis}} \) )?}

Compound (X) [Phenylacetylene] is subjected to the sequence of reactions:

Molar mass of the major product (Y) formed is _______ \(g \cdot mol^{-1}\). (Given molar mass in \(g \cdot mol^{-1}\) C:12, H: 1, O: 16)

Consider the metal complexes \( [Ni(en)_3]^{2+} \) (A), \( [NiCl_4]^{2-} \) (B) and \( [Ni(NH_3)_6]^{2+} \) (C). Choose the CORRECT option by considering the number of unpaired electrons present in (A), (B) and (C) respectively and the order of frequency of absorption.

In sulphur estimation, \(2.0 \times 10^{-3}\) mol of an organic compound (X) (molar mass 76 \(g \cdot mol^{-1}\)) gave 0.4813 g of barium sulphate (molar mass 233 \(g \cdot mol^{-1}\)). The percentage of sulphur in the compound (X) is _______ \(\times 10^{-1}\) % (Nearest integer)

The descending order of acidity among the following compounds is :

The \( 1^{\text{st}} \) ionization enthalpy for Mg is +737 kJ/mol. The most probable estimated value of the \( 2^{\text{nd}} \) ionization enthalpy of Mg is _______ kJ/mol.

Three different reactions were started with identical initial concentration of reactants. Which of the following statement is correct regarding the given graph showing variation of reactant concentration with time?

The species having identical radii according to the Bohr's theory are:
A. H (first orbit)
B. \( He^+ \) (first orbit)
C. \( He^+ \) (Second orbit)
D. \( Li^{2+} \) (first orbit)
E. \( Be^{3+} \) (Second orbit)
Choose the correct answer from the options given below:

For the following reaction at 50 \(^\circ\)C and at 2 atm pressure,
\(2N_2O_5(g) \rightleftharpoons 2N_2O_4(g) + O_2(g)\)
\(N_2O_5\) is 50% dissociated. The magnitude of standard free energy change at this temperature is x.
x = _______ J \(\cdot mol^{-1}\) [Nearest integer].
Given : R = 8.314 J \(mol^{-1} K^{-1}\), \(\log 2 = 0.30, \log 3 = 0.48, \ln 10 = 2.303, ^\circ C + 273 = K\)

Match the LIST-I with LIST-II: }

Among \(Fe^{3+}, Pb^{2+}, Cu^{2+}\) and \(Mn^{2+}\), identify the one that gets precipitated out while passing \(H_2S\) in presence of \(NH_4OH\) as group reagent. The highest possible oxidation state of the corresponding metal is:

Given below are two statements:
Statement I: The correct order of electronegativity of fluorine, oxygen and nitrogen is \(F>O>N\).
Statement II: The oxidation state of oxygen in \(OF_2\) is \(+2\) and in \(Na_2O\) is \(-2\).

Identify the correct statements.
A. Glucose exists in two anomeric forms.
B. Anomers of glucose differ in configuration at C-1 in cyclic hemiacetal structure.
C. Melting point of \(\alpha\)-anomer of glucose is greater than \(\beta\)-anomer.
D. Specific rotation of \(\alpha\)-anomer is \(+19^\circ\) while for \(\beta\)-anomer is \(+112^\circ\).
E. \(\alpha\) and \(\beta\) anomers of glucose are prepared by crystallization of saturated glucose solution at \(303 \text{ K}\) and \(371 \text{ K}\) respectively.

Given below are two statements:
Statement I: Sodium dichromate and potassium dichromate are classified as primary standards in titrimetric analysis.
Statement II: Phenolphthalein is a weak base, therefore it dissociates in acidic medium.

Which of the following is NOT a physical or chemical characteristic of interstitial compounds?

The correct statements about metal carbonyls are:
A. The metal-carbon bonds in metal carbonyls possess both \(\sigma\) and \(\pi\) character.
B. Due to synergic bonding interactions between metal and CO ligand, the metal-carbon bond becomes weak.
C. The metal-carbon \(\sigma\) bond is formed by the donation of lone pair of electrons on the carbonyl carbon into a vacant orbital of metal.
D. The metal-carbon \(\pi\) bond is formed by the donation of electrons from filled d-orbital of metal into vacant \(\pi^*\) orbital of CO.

Consider the following species:
\(BrF_5, XeF_5^-, BF_4^-, ICl_4^-, XeF_4, SF_4, NH_4^+, ClF_3, XeF_2, ICl_2^-\)
Number of species having \(sp^3d\) hybridized central atom is ____.

Correct statements from the following are:
A. Nitrogen in oxidation states from \(+1\) to \(+4\) disproportionates in acid medium.
B. Nitrogen has the ability to form \(d\pi - p\pi\) multiple bonds with itself and other elements with small size and high electronegativity.
C. N-N single bond is stronger than P-P single bond.
D. Nitrogen has highest density in its group due to small size.
E. The maximum covalency of nitrogen is four since it has only four valence orbitals for bonding.

Benzyl isocyanide can be obtained from}

The values of pressure equilibrium constant recorded at different temperatures for the following equilibrium reaction have been given below:
\(A(g) \rightleftharpoons B(g) + C(g)\)}

The magnitude of \(\frac{\Delta H^\circ}{R}\) calculated from the above data is ____. (Nearest integer)}

One mole of phenol is treated with dilute \(HNO_3\) at \(298 \text{ K}\) to give a mixture of products. The mixture is separated by steam distillation. The steam volatile compound (X) is separated. The increase in percentage of oxygen in (X) with respect to phenol is ____ \(\times 10^{-1}\) %.
(Given molar mass in \(\text{g mol}^{-1}\) H:1, C:12, N:14, O:16)}

For the following Friedel Craft's alkylation reaction, which of the statements are correct?}

A. Major product is n-propyl benzene.
B. iso-propyl carbocation intermediate is also generated.
C. Multiple substitution is inevitable.
D. Introducing electron-donating substituent on benzene will not produce any alkyl benzene.

Identify the incorrect statements.

In an estimation of sulphur by Carius method \(0.2 \text{ g}\) of the substance gave \(0.6 \text{ g}\) of \(BaSO_4\). The percentage of sulphur in the substance is ____ %.
(Given molar mass in \(\text{g mol}^{-1}\) S : 32, \(BaSO_4 : 231\))}