List of top Chemistry Questions

Identify the complex ion which does not exist.

The mass of sodium hydroxide that must be dissolved in \(1.0\,\text{L}\) solution to get pH of \(12\) is

If the kinetic energy of the molecules in \(8.0\,\text{g}\) methane at \(47^\circ\text{C}\) is \(x\,\text{kJ}\), then the kinetic energy (in kJ) of the molecules in the same amount of dihydrogen at \(127^\circ\text{C}\) is

In which of the following hydrogen bond does not exist?

Consider the two redox reactions I and II \[ \text{I. }2\mathrm{Na_2S_2O_3}+ \mathrm{I_2} \rightarrow \mathrm{Na_2S_4O_6}+2\mathrm{NaI} \] \[ \text{II. }2\mathrm{KMnO_4}+10\mathrm{FeSO_4}+3\mathrm{H_2SO_4} \rightarrow 2\mathrm{MnSO_4}+5\mathrm{Fe_2(SO_4)_3}+2\mathrm{K_2SO_4}+3\mathrm{H_2O} \] The ratio of equivalent weights of \(\mathrm{KMnO_4}\) and \(\mathrm{Na_2S_2O_3}\) is \[ (\mathrm{K}=39u;\ \mathrm{Mn}=55u;\ \mathrm{O}=16u;\ \mathrm{Na}=23u;\ \mathrm{S}=32u) \]

The correct orders of ionization enthalpies of the given elements are \[ \begin{aligned} \text{I. }& \mathrm{Li}>\mathrm{B}>\mathrm{Be}>\mathrm{Mg} \text{II. }& \mathrm{P}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Na} \text{III. }& \mathrm{O}>\mathrm{F}>\mathrm{N}>\mathrm{C} \end{aligned} \] The correct answer is

Identify the element, which does not belong to the fifth period of the long form of periodic table.

The mass of iron converted into \(Fe_3O_4\) by the action of \(18\) g of steam is: (Given: Molar mass of H, O and Fe are \(1, 16\) and \(56\) g mol\(^{-1}\) respectively). Assume iron is present in excess.

Consider the isomers of hydrocarbon with molecular formula \(C_5H_{10}\). These isomers do not decolourise \(KMnO_4\) solution. These isomers are subjected to chlorination with chlorine in presence of light to give monochloro compounds. The total number of monochloro compounds (structural isomers only) formed is ______.}

The solubility product of \(PbCl_2\) at \(298\ \text{K}\) is \(3.2 \times 10^{-5}\). What is its solubility in \(\text{mol dm}^{-3}\)?

What is the pH of a weak dibasic acid that is 2% dissociated in its M/100 solution at 298 K?

Match the following.

\[ \begin{array}{|c|c|c|c|} \hline \text{List-I} & \text{Atomic number} & \text{List-II} & \text{Group} \\ \hline \text{A} & 53 & \text{I} & 16 \\ \hline \text{B} & 34 & \text{II} & 2 \\ \hline \text{C} & 38 & \text{III} & 17 \\ \hline \text{D} & 49 & \text{IV} & 13 \\ \hline & & \text{V} & 7 \\ \hline \end{array} \]
The correct answer is

Which of the following pairs contain isostructural species? \[ \begin{aligned} \text{I. } & \mathrm{H_3PO_3,\ H_2SO_4} \\ \text{II. } & \mathrm{SO_3,\ BF_3} \\ \text{III. } & \mathrm{O_3,\ NO_2^-} \end{aligned} \] The correct answer is

At \(T(\mathrm{K})\), decomposition of \(A(g)\) follows first order kinetics.

\[ A(g) \rightarrow B(g) + C(g) \]
The following data is obtained for this reaction.

\[ \begin{array}{|c|c|} \hline \text{Time (s)} & \text{Total pressure (atm)} \\ \hline 0 & 0.5 \\ \hline 100 & 0.6 \\ \hline \end{array} \]
What is the rate constant (in \(\mathrm{s^{-1}}\)) for this reaction?

\[ \left(\log 1.25 = 0.097,\; \log 1.666 = 0.222\right) \]

Match the following.

\[ \begin{array}{|c|l|c|l|} \hline \text{List-I} & & \text{List-II} & \\ \hline \text{A} & \text{Cottrell precipitator} & \text{I} & \text{Antimony colloid} \\ \hline \text{B} & \text{Kalaazar} & \text{II} & \text{Curd} \\ \hline \text{C} & \text{Lactobacilli} & \text{III} & \text{Drinking water} \\ \hline \text{D} & \text{Alum} & \text{IV} & \text{Smoke} \\ \hline \end{array} \]
The correct answer is

Which of the following reactions gives oxide of nitrogen which is in solid state and acidic in nature? \[ \begin{aligned} \text{I. }&\mathrm{NH_4NO_3}\xrightarrow{\Delta} \\ \text{II. }& 2\mathrm{Pb(NO_3)_2}\xrightarrow{\Delta} \\ \text{III. }&\mathrm{P_4O_{10}+4HNO_3}\rightarrow \\ \text{IV. }& 2\mathrm{NO}+\mathrm{N_2O_4}\xrightarrow[250\,K]{} \end{aligned} \] The correct answer is

The reactions which produce \(\mathrm{O_2}\) are \[ \begin{aligned} \text{I. }& 2\mathrm{KClO_3}\\ \xrightarrow[\mathrm{MnO_2}]{\Delta} \\ \text{II. }& 2\mathrm{KMnO_4}\\ \xrightarrow{\Delta} \\ \text{III. }&(\mathrm{NH_4})_2\mathrm{Cr_2O_7} \xrightarrow{\Delta} \end{aligned} \] The correct answer is

Which of the following oxidation reactions of \(\mathrm{KMnO_4}\) occur in acidic medium? \[ \begin{aligned} \text{I. }&\text{Oxidation of oxalic acid} \\ \text{II. }&\text{Oxidation of iodide to iodate} \\ \text{III. }&\text{Precipitation of sulphur from hydrogen sulphide} \end{aligned} \] The correct answer is

Benzene nitrile on reaction with reagent (A) gave product (X). In another reaction with reagent (B) gave product (Y). \(X\) and \(Y\) both form oxime but only \(Y\) gets oxidized with ammoniacal silver nitrate solution. The correct reagents \(A\) and \(B\) respectively are \[ \begin{aligned} \text{I. }&\mathrm{CH_3CH_2MgBr,\ H_2O} \qquad;\qquad \mathrm{DIBAL\!-\!H,\ H_2O} \text{II. }&(\mathrm{CH_3CH_2})_2\mathrm{Cd} \qquad;\qquad \mathrm{SnCl_2+HCl,\ H_2O} \text{III. }&\mathrm{CH_3CH_2MgBr,\ H_2O} \qquad;\qquad \mathrm{SnCl_2+HCl,\ H_2O} \text{IV. }&(\mathrm{CH_3CH_2})_2\mathrm{Cd} \qquad;\qquad \mathrm{DIBAL\!-\!H,\ H_2O} \end{aligned} \] The correct answer is

\[ \mathrm{C_6H_5NH_2} \xrightarrow[\;273{-}278\,K\;]{\mathrm{HNO_2/HCl}} X \xrightarrow{\mathrm{Cu_2Cl_2}} Y \] Conversion of \(X\) to \(Y\) is called

Observe the following reaction sequence \[ \text{Styrene} \xrightarrow[\left(\mathrm{C_6H_5CO}\right)_2\mathrm{O_2}]{\mathrm{HBr}} X \xrightarrow[(ii)\ \mathrm{H_3O^+}]{(i)\ \mathrm{KCN}} Y \xrightarrow[(ii)\ \mathrm{H_2O}]{(i)\ \mathrm{Br_2/red\ P}} Z \] The correct statement regarding \(Y\) and \(Z\) is

Consider the given sequence of reactions

The compound \(D\) cannot be obtained by

What are \(X,\;Y,\;Z\) respectively in the following reaction sequence?