List of top Chemistry Questions

Consider the following redox reaction taking place in acidic medium: \[ \mathrm{BH_4^- (aq) + ClO_3^- (aq) \rightarrow H_2BO_3^- (aq) + Cl^- (aq)} \] If the Nernst equation for the above balanced reaction is \[ E_{\text{cell}} = E^\circ_{\text{cell}} - \frac{RT}{nF}\ln Q, \] then the value of $n$ is ________ (Nearest integer).

$X$ is the number of geometrical isomers exhibited by $[\mathrm{Pt(NH_3)(H_2O)BrCl}]$.
$Y$ is the number of optically inactive isomer(s) exhibited by $[\mathrm{CrCl_2(ox)_2}]^{3-}$.
$Z$ is the number of geometrical isomers exhibited by $[\mathrm{Co(NH_3)_3(NO_2)_3}]$. Find the value of $X + Y + Z$. }

The correct order of stability for the following carbanions is: \[ \text{CH}_2=\text{CH}^- ,\quad \text{CH}_3-\text{CH}_2^- ,\quad \text{CH}\equiv\text{C}^- \]

The correct statement among the following is:

Regarding the hydrides of group 15 elements $EH_3$ $(E = N, P, As, Sb)$, select the correct statement(s):
[A.] The stability of hydrides decreases down the group.
[B.] The basicity of hydrides decreases down the group.
[C.] The reducing character increases down the group.
[D.] The boiling point increases down the group. Choose the correct answer:

Method used for separation of mixture of products (B and C) obtained in the following reaction is:

Given below are two statements: Statement I: Griess–Ilosvay test is used for the detection of nitrite ion, which involves the use of sulphanilic acid and $\alpha$-naphthylamine reagent. Statement II: In the above test, sulphanilic acid is diazotized by the acidified nitrite ion, which on further coupling with $\alpha$-naphthylamine forms an azo-dye. In the light of the above statements, choose the correct answer from the options given below.

Consider the reaction: \[ \text{Ph–CH=CH}_2 \xrightarrow[\text{peroxide}]{\text{HBr}} \text{Product} \] Which of the following statements are correct?
[A.] The reaction proceeds through a more stable radical intermediate.
[B.] The role of peroxide is to generate $\mathrm{H^\bullet}$ radical.
[C.] During this reaction, benzene is formed as a byproduct.
[D.] $1$-Bromo-$2$-phenylethane is formed as a minor product.
[E.] The same reaction in absence of peroxide proceeds via a carbocation intermediate. Choose the correct answer.

Consider the dissociation equilibrium of the following weak acid: \[ \mathrm{HA \rightleftharpoons H^+(aq) + A^-(aq)} \] If the $pK_a$ of the acid is $4$, then the pH of a $10\ \text{mM}$ HA solution is ________ (Nearest integer). (Given: The degree of dissociation can be neglected with respect to unity)

The wave numbers of three spectral lines of hydrogen atom are considered. Identify the set of spectral lines belonging to the {Balmer series. ($R$ = Rydberg constant)}

$0.53\ \text{g}$ of an organic compound $X$ when heated with excess concentrated nitric acid and then with silver nitrate gave $0.75\ \text{g}$ of silver bromide precipitate. $1.0\ \text{g}$ of $X$ gave $1.32\ \text{g}$ of $\mathrm{CO_2}$ on combustion. Find the percentage of hydrogen in compound $X$. (Nearest integer) [Given: Atomic masses (g mol$^{-1}$): H = 1, C = 12, Br = 80, Ag = 108, O = 16]

At temperature $T$ K, $2$ moles of liquid $A$ and $3$ moles of liquid $B$ are mixed. The vapour pressure of the ideal solution formed is $320$ mm Hg. At this stage, one mole of $A$ and one mole of $B$ are added to the solution. The vapour pressure is now measured as $328.6$ mm Hg. The vapour pressures (in mm Hg) of pure $A$ and pure $B$ respectively are:

The figures below show: Which of the following points in Figure 2 most accurately represents the nodal surface shown in Figure 1?

In period 4 of the periodic table, the elements with highest and lowest atomic radii respectively are:

$20.0\,\text{dm}^3$ of an ideal gas $X$ at $600$ K and $0.5$ MPa undergoes isothermal reversible expansion until the pressure of the gas becomes $0.2$ MPa. Which of the following option is correct? (Given: $\log 2 = 0.3010$, $\log 5 = 0.6989$)

From the following, how many compounds contain at least one secondary alcohol?

At 298 K, the mole percentage of N$_2$(g) in air is 80%. Water is in equilibrium with air at a pressure of 10 atm. What is the mole fraction of N$_2$(g) in water at 298 K? ($K_H$ for N$_2$ = $6.5 \times 10^7$ mm Hg)

The number of possible tripeptides formed involving alanine (ala), glycine (gly) and valine (val), where no amino acid has been used more than once is

A student has planned to prepare acetanilide from aniline using acetic anhydride. The student has started from 9.3 g of aniline. However, the student has managed to obtain 11 g of dry acetanilide. The % yield of this reaction is

In the group analysis of cations, Ba$^{2+}$ & Ca$^{2+}$ are precipitated respectively as

The correct order of C, N, O and F in terms of second ionisation potential is

The heat of atomisation of methane and ethane are $ x $ kJ mol$^{-1}$ and $ y $ kJ mol$^{-1}$ respectively. The longest wavelength ($ \lambda $) of light capable of breaking the C–C bond can be expressed in SI unit as:

Find out the statements which are not true.
A. Resonating structures with more covalent bonds and less charge separation are more stable.
B. In electromeric effect, an unsaturated system shows +E effect with nucleophile and –E effect with electrophile.
C. Inductive effect is responsible for high melting point, boiling point and dipole moment of polar compounds.
D. The greater the number of alkyl groups attached to the doubly bonded carbon atoms, higher is the heat of hydrogenation.
E. Stability of carbanion increases with increase in s-character of the carbon carrying negative charge.

The wavelength of spectral line obtained in the spectrum of Li$^{2+}$ ion, when the transition takes place between two levels whose sum is 4 and difference is 2, is

Pair of species among the following having same bond order as well as paramagnetic character will be: