List of top Questions asked in JEE Main- 2021

An empty LPG cylinder weighs 14.8 kg. When full, it weighs 29.0 kg and shows a pressure of 3.47 atm. In the course of use at ambient temperature, the mass of the cylinder is reduced to 23.0 kg. The final pressure inside of the cylinder is _________ atm. (Nearest integer)

(Assume LPG of be an ideal gas)

The sum of oxidation states of two silver ions in \(\mathrm{[Ag(NH_3)_2][Ag(CN)_2]}\) complex is _____________.

The number of atoms in 8g of sodium is x \(\times\) 10\(^{23}\). The value of x is ____________. (Nearest integer)

[Given : \(N_A = 6.02 \times 10^{23}\ \mathrm{mol^{-1}}\)

Atomic mass of Na = 23.0 u]

A 50 watt bulb emits monochromatic red light of wavelength of 795 nm. The number of photons emitted per second by the bulb is x \(\times\) 10\(^{20}\). The value of x is __________. [Given : h = 6.63 \(\times\) 10\(^{-34}\) Js and c = 3.0 \(\times\) 10\(^8\) ms\(^{-1}\)]

The spin-only magnetic moment value of \(\mathrm{B_2^+}\) species is _____________ \(\times 10^{-2}\) BM. (Nearest integer)
[Given : \(\sqrt{3} = 1.73\)]

If the conductivity of mercury at \(0^\circ\mathrm{C}\) is \(1.07 \times 10^{6}\ \mathrm{S\,m^{-1}}\) and the resistance of a cell containing mercury is \(0.243\ \Omega\), then the cell constant of the cell is \(x \times 10^{4}\ \mathrm{m^{-1}}\). The value of x is ____________. (Nearest integer)

If 80 g of copper sulphate \(\mathrm{CuSO_4 \cdot 5H_2O}\) is dissolved in deionised water to make 5L of solution. The concentration of the copper sulphate solution is x \(\times\) 10\(^{-3}\) mol L\(^{-1}\). The value of x is _____________.

[Atomic masses Cu : 63.54u, S : 32u, O : 16u, H : 1u]

Match List - I with List - II :

	List - I (Colloid Preparation Method)		List - II (Chemical Reaction)
(a)	Hydrolysis	(i)	\(\mathrm{2AuCl_3 + 3HCHO + 3H_2O \to 2Au(sol) + 3HCOOH + 6HCl}\)
(b)	Reduction	(ii)	\(\mathrm{As_2O_3 + 3H_2S \to As_2S_3(sol) + 3H_2O}\)
(c)	Oxidation	(iii)	\(\mathrm{SO_2 + 2H_2S \to 3S(sol) + 2H_2O}\)
(d)	Double Decomposition	(iv)	\(\mathrm{FeCl_3 + 3H_2O \to Fe(OH)_3(sol) + 3HCl}\)

Choose the most appropriate answer from the options given below.

Monomer units of Dacron polymer are :

Calamine and Malachite, respectively, are the ores of :

The potassium ferrocyanide solution gives a Prussian blue colour, when added to :

Hydrogen peroxide reacts with iodine in basic medium to give :

The oxide without nitrogen-nitrogen bond is :

Number of paramagnetic oxides among the following given oxides is ____________.

\(\mathrm{Li_2O}\), \(\mathrm{CaO}\), \(\mathrm{Na_2O_2}\), \(\mathrm{KO_2}\), \(\mathrm{MgO}\) and \(\mathrm{K_2O}\)

In the following sequence of reactions, \(\mathrm{C_3H_6 \xrightarrow{H^+/H_2O} A \xrightarrow[\text{dil KOH}]{KIO} B + C}\)
The compounds B and C respectively are :-

Given below are two statements :

Statement I : The nucleophilic addition of sodium hydrogen sulphite to an aldehyde or a ketone involves proton transfer to form a stable ion.

Statement II : The nucleophilic addition of hydrogen cyanide to an aldehyde or a ketone yields amine as final product.

In the light of the above statements, choose the most appropriate answer from the options given below :

The stereoisomers that are formed by electrophilic addition of bromine to trans-but-2-ene is/are :

Which one of the following gives the most stable Diazonium salt?

In the following sequence of reactions a compound A, (molecular formula \(\mathrm{C_6H_{12}O_2}\)) with a straight chain structure gives a \(\mathrm{C_4}\) carboxylic acid. A is :
\(\mathrm{A}\ \xrightarrow[\mathrm{H_3O^+}]{\mathrm{LiAlH_4}}\ \mathrm{B}\ \xrightarrow{\text{Oxidation}}\ \mathrm{C_4}\text{-carboxylic acid}\)

Which one of the following compounds is aromatic in nature?

Identify A in the following reaction.

In the given chemical reaction, colors of the \(\mathrm{Fe^{2+}}\) and \(\mathrm{Fe^{3+}}\) ions, are respectively :
\(5\mathrm{Fe^{2+}} + \mathrm{MnO_4^-} + 8\mathrm{H^+} \rightarrow \mathrm{Mn^{2+}} + 4\mathrm{H_2O} + 5\mathrm{Fe^{3+}}\)

Which one of the following given graphs represents the variation of rate constant (k) with temperature (T) for an endothermic reaction?

The Crystal Field Stabilization Energy (CFSE) and magnetic moment (spin-only) of an octahedral aqua complex of a metal ion (\(\mathrm{M^{z+}}\)) are \(-0.8\,\Delta_0\) and 3.87 BM, respectively. Identify (\(\mathrm{M^{z+}}\)) :

A uniform heating wire of resistance \(36\ \Omega\) is connected across a potential difference of 240 V. The wire is then cut into half and potential difference of 240 V is applied across each half separately. The ratio of power dissipation in first case to the total power dissipation in the second case would be \(1 : x\), where \(x\) is ____________.