List of top Chemistry Questions asked in JEE Main

Class XII students were asked to prepare one litre of buffer solution of pH \(8.26\) by their Chemistry teacher. The amount of ammonium chloride to be dissolved by the student in \(0.2\) M ammonia solution to make one litre of the buffer is (Given : \(pK_b\) \((NH_3)\) = \(4.74\), Molar mass of \(NH_3\) = \(17\) g \(mol^{–1}\), Molar mass of \(NH_4Cl\) = \(53.5\) \(g\) \(mol^{–1}\))

A gas (Molar mass = 280 g mol^–1) was burnt in excess O₂ in a constant volume calorimeter and during combustion the temperature of calorimeter increased from 298.0 K to 298.45 K. If the heat capacity of calorimeter is 2.5 kJ K^–1 and enthalpy of combustion of gas is 9 kJ mol^–1 then amount of gas burnt is __________g. (Nearest Integer).

2.4 g coal is burnt in a bomb calorimeter in excess of oxygen at 298 K and 1 atm pressure. The temperature of the calorimeter rises from 298 K to 300 K. The enthalpy change during the combustion of coal is –x kJ mol^–1. The value of x is ______.(Nearest integer)
(Given : Heat capacity of bomb calorimeter is 20.0 kJ K^–1. Assume coal to be pure carbon)

When 600 mL of 0.2 M HNO₃ is mixed with 400 mL of 0.1 M NaOH solution in a flask, the rise in temperature of the flask is ________ × 10^–2 °C.
(Enthalpy of neutralisation = 57 kJ mol^–1 and Specific heat of water = 4.2 JK^–1 g^–1)
(Neglect heat capacity of flask)

At 600 K, 2 mol of NO are mixed with 1 mol of \(O_2\). 

The reaction occurring as above comes to equilibrium under a total pressure of 1 atm. Analysis of the system shows that 0.6 mol of oxygen are present at equilibrium. The equilibrium constant for the reaction is _______. (Nearest integer)

The wavelength of an electron and a neutron will become equal when the velocity of the electron is x times the velocity of neutron. The value of x is ______. (Nearest integer)
(Mass of electron is 9.1 × 10^–31 kg and mass of neutron is 1.6 × 10^–27 kg)

When 5 moles of He gas expand isothermally and reversibly at 300 K from 10 litre to 20 litre, the magnitude of the maximum work obtained is _____ J. [nearest integer] (Given : R = 8.3 J K^–1 mol^–1 and log 2 = 0.3010)

2NO + 2H₂ → N₂ + 2H₂O
The above reaction has been studied at 800 °C. The related data is given in the table below.
The order of the reaction with respect to NO is ___.

When a certain amount of solid A is dissolved in 100 g of water at 25°C to make a dilute solution, the vapour pressure of the solution is reduced to one-half of that of pure water. The vapour pressure of pure water is 23.76 mmHg. The number of moles of solute A added is _________. (Nearest Integer).

A 2.0 g sample containing MnO₂ is treated with HCl liberating Cl₂. The Cl₂ gas is passed into a solution of KI and 60.0 mL of 0.1 M Na₂S₂O₃ is required to titrate the liberated iodine. The percentage of MnO₂ in the sample is ______. (Nearest integer)
[Atomic masses (in u) Mn = 55; Cl = 35.5; O = 16, I = 127, Na = 23, K = 39, S = 32]

Ka₁, Ka₂ and Ka₃ are the respective ionization constants for the following reactions (a),(b), and (c).
(a) H₂C₂O₄⇌H⁺+HC₂O₄⁻
(b) HC₂O₄⁻⇌H⁺+HC₂O₄²⁻
(c) H₂C₂O₄⇌2H⁺+_C2O₄²⁻
The relationship between Ka₁,Ka₂ and Ka₃ is given as

‘x’ g of molecular oxygen (O₂) is mixed with 200 g of neon (Ne). The total pressure of the non-reactive mixture of O₂ and Ne in the cylinder is 25 bar. The partial pressure of Ne is 20 bar at the same temperature and volume. The value of ‘x’ is ___.
[Given : Molar mass of O₂ = 32 g mol^–1 and Molar mass of Ne = 20 g mol^–1]

While performing a thermodynamics experiment, a student made the following observations.
HCl + NaOH \(\rightarrow\) NaCl + H₂O; ΔH = – 57.3 kJ mol^–1
CH₃COOH + NaOH \(\rightarrow\) CH₃COONa + H₂O; ΔH = –55.3 kJ mol^–1
The enthalpy of ionization of CH₃COOH, as calculated by the student, is ______ kJ mol^–1. [nearest integer]

At 310 K, the solubility of CaF₂ in water is 2.34 ×10^–3 g/100 mL. The solubility product of CaF₂ is _____ × 10^–8 (mol/L)³.
(Given molar mass : CaF₂ = 78 g mol^–1).

When 800 mL of 0.5 M nitric acid is heated in a beaker, its volume is reduced to half and 11.5 g of nitric acid is evaporated. The molarity of the remaining nitric acid solution is \(x × 10^{–2} M\). (Nearest integer)
(Molar mass of nitric acid is 63 g mol^–1)

A flask is filled with equal moles of A and B. The half lives of A and B are 100 s and 50 s respectively and are independent of the initial concentration. The time required for the concentration of A to be four times that of B is ________s.
(Given : In 2 = 0.693)

Number of electron deficient molecules among the following
\(PH_3, B_2H_6, CCl_4, NH_3, LiH \) and \(BCl_3\) is

A \(100\) \(mL\) solution of \(CH_3CH_2MgBr\) on treatment with methanol produces \(2.24\) \(mL\) of a gas at STP. The weight of gas produced is_____ mg. [nearest integer]

Consider the reaction
\(4\text{HNO}_3(\text{l}) + 3\text{KCl}(\text{s}) \rightarrow \text{Cl}_2(\text{g}) + \text{NOCl}(\text{g}) + 2\text{H}_2\text{O}(\text{g}) + 3\text{KNO}_3(\text{s})\)
The amount of HNO₃ required to produce 110.0 g of KNO₃ is
(Given : Atomic masses of H, O, N and K are 1, 16, 14 and 39 respectively.)

Which of the following structures are aromatic in nature?

Compound ‘P’ on nitration with dil. HNO₃ yields two isomers (A) and (B) show the intramolecular and intermolecular hydrogen bonding respectively. Compound (P) on reaction with conc. HNO₃ yields a yellow compound ‘C’, a strong acid. The number of oxygen atoms is present in compound ‘C’ _____

L-isomer of a compound ‘A’ \((C_4H_8O_4)\) gives a positive test with \([Ag(NH_3)^2]^+\). Treatment of ‘A’ with acetic anhydride yields triacetate derivative. Compound ‘A’ produces an optically active compound (B) and an optically inactive compound (C) on treatment with bromine water and \(HNO_3\) respectively. Compound (A) is:

For combustion of one mole of magnesium in an open container at 300K and 1bar pressure, Δ_CH^Θ=–601.70kJ mol^–1, the magnitude of change in internal energy for the reaction is______ kJ. (Nearest integer) (Given : R = 8.3 J K^–1 mol^–1)

The cell potential for \(\text{Zn}|\text{Zn}^{2+}\text{(aq)}||\text{Sn}^{x+}|\text{Sn}\) is 0.801 V at 298 K.The reaction quotient for the above reaction is 10^–2. The number of electrons involved in the given electrochemical cell reaction is _____. (Given: \(Eº_Zn^{2+}\)|Zn=-0.763V,Eºsn^x+|sn=+0.008V and 2.303RT/F=0.06V)