List of top Chemistry Questions

State Kohlrausch's law of independent migration of ions. With the help of a curve, explain why it is not easy to determine \(\Lambda_m^\circ\) for weak electrolytes by extrapolating the concentration--molar conductivity curve, as it is for strong electrolytes.

The half-life period of a radioactive element is \(1.5 \times 10^{10}\) years. Calculate the time in which the activity of the element is reduced to 75% of its original value. \[ \text{Given : } \log 2 = 0.30,\; \log 3 = 0.48,\; \log 4 = 0.60 \]

How will you obtain the following from benzene diazonium chloride ? Write chemical equations involved : (c) p-Aminoazobenzene

An organic compound (A) with molecular formula C$_3$H$_5$N on reaction with C$_6$H$_5$MgBr followed by hydrolysis, gives a compound (B). Compound (B) forms an orange-red precipitate with 2,4-DNP reagent and does not give iodoform test. It neither reduces Tollens' or Fehling's reagent nor does it decolourise bromine water. On drastic oxidation with chromic acid it gives a carboxylic acid (C) having molecular formula C$_7$H$_6$O$_2$. Identify the compounds (A), (B) and (C). Write the reactions of compound (A) with C$_6$H$_5$MgBr followed by hydrolysis to give compound (B).

How will you obtain the following from benzene diazonium chloride ? Write chemical equations involved : (b) Iodobenzene

An antifreeze solution is prepared by dissolving 31 g of ethylene glycol (Molar mass = 62 g mol$^{-1}$) in 600 g of water. Calculate the freezing point of the solution. (K$_f$ for water = 1.86 K kg mol$^{-1}$)

Give reasons for the following : (c) CH$_3$--I is more reactive than CH$_3$--Br towards SN2 reactions.

How will you obtain the following from benzene diazonium chloride ? Write chemical equations involved : (a) Phenol

For a reaction A + B $\rightarrow$ Products, the rate law is : \[ \text{Rate} = k[A]^{\frac{3}{2}}[B] \] Write the overall order of the reaction. Can this reaction be an elementary reaction ? Give reason in support of your answer.

How do you explain the following ? (a) Presence of a carbonyl group in glucose (b) Presence of five --OH groups in glucose

Give reasons for the following : (a) Alkyl halides, though polar, yet their solubility in water is very low.

Give reasons for the following : (b) p-Dichlorobenzene has higher melting point than those of o- and m-isomers.

For the compound having molecular formula C$_4$H$_9$Br, write : (a) the isomer which is most reactive towards SN1 displacement. (b) the isomer which, on reacting with Na metal in the presence of dry ether, gives 2,5-Dimethylhexane.

Assertion (A) : Order of reaction is not applicable for elementary reaction but applicable for complex reaction. Reason (R) : Order of reaction is an experimental quantity.

Explain why, on addition of 1 mol of KCl to 1 litre of water, the boiling point of water increases, while the addition of 1 mol of methyl alcohol to 1 litre of water decreases the boiling point.

Assertion (A) : Phenol is more acidic than 4-methylphenol. Reason (R) : The presence of an electron releasing group in phenol makes it more acidic.

Write IUPAC names of the following compounds : \[ (i)\ [PtCl_2(en)_2]SO_4 \] \[ (ii)\ (NH_4)_2[CoF_4] \]

Assertion (A) : Aromatic primary amines can easily be prepared by Gabriel phthalimide synthesis. Reason (R) : Gabriel phthalimide synthesis is used to prepare only aliphatic primary amines.

Define the following terms with a suitable example in each case : \[ (i)\ \text{Ambidentate ligand} \] \[ (ii)\ \text{Double salt} \]

In aqueous acidified solution, CrO$_4^{2-}$ ion converts to which of the following ?

For the reaction \(2A \rightarrow 3B\), the rate of reaction \(\frac{d[B]}{dt}\) is equal to :

Assertion (A) : Separation of Zr and Hf is difficult. Reason (R) : Zr and Hf have almost identical atomic and ionic radii due to lanthanoid contraction.

The boiling point of an azeotropic mixture of water and nitric acid is more than that of pure water and nitric acid. The mixture shows :

On hydrolysis, which of the following carbohydrates gives only glucose ?

Among the following, which one has the lowest value of pK$_b$ ?