List of top Chemistry Questions asked in CBSE CLASS XII

Name the oxometal anions of the first series of the transition metals in which the metal exhibits the oxidation state equal to its group number.

The time required for 10% completion of a first order reaction at 298 K is equal to that required for its 25% completion at 308 K. If the value of A is \(4 \times 10^{10} s^{-1}\) . Calculate \(k\) at 318 K and \(E_a\).
The oxidation number of cobalt in \(K[Co(CO)_4]\) is
The following data were obtained during the first order thermal decomposition of \(SO_2Cl_2\) at a constant volume.
\(SO_2Cl_2(g) → SO_2(g) + Cl_2(g)\)
ExperimentTime/s-1Total pressure/atm
100.5
21000.6
Calculate the rate of the reaction when total pressure is 0.65 atm.
Predict the products of electrolysis in each of the following: 
 (i) An aqueous solution of AgNO3 with silver electrodes. 
 (ii) An aqueous solution of AgNO3 with platinum electrodes. 
 (iii) A dilute solution of H2SO4 with platinum electrodes. 
 (iv) An aqueous solution of CuCl2 with platinum electrodes.
An antifreeze solution is prepared from 222.6 g of ethylene glycol C2H6O2 and 200 g of water. Calculate the molality of the solution. If the density of the solution is 1.072 g mL–1, then what shall be the molarity of the solution?
Although the details of the structure of monoclinic sulphur are not well known it probably consists of
What role does the molecular interaction play in a solution of alcohol and water?

Write chemical reaction for the preparation of phenol from chlorobenzene. 

Three electrolytic cells A,B,C containing solutions of ZnSO4, AgNO3 and CuSO4, respectively are connected in series. A steady current of 1.5 amperes was passed through them until 1.45 g of silver deposited at the cathode of cell B. How long did the current flow? What mass of copper and zinc were deposited?

A solution containing 30 g of non-volatile solute exactly in 90 g of water has a vapour pressure of 2.8 kPa at 298 K. Further, 18 g of water is then added to the solution and the new vapour pressure becomes 2.9 Pa at 298 K. Calculate:
(i) molar mass of the solute 
(ii) vapour pressure of water at 298 K.
What is meant by positive and negative deviations from Raoult's law and how is the sign of \(∆_{mix}H\) related to positive and negative deviations from Raoult's law?

Name the members of the lanthanoid series which exhibit +4 oxidation state and those which exhibit +2 oxidation state. Try to correlate this type of behavior with the electronic configurations of these elements.

List various types of isomerism possible for coordination compounds, giving an example of each

An organic compound with the molecular formula \( C_9H_{10}\)O forms \(2,4-DNP\) derivative,reduces Tollens’ reagent and undergoes Cannizzaro reaction.On vigorous oxidation,it gives \(1,2-benzenedicarboxylic\) acid.Identify the compound.
 

Give examples and suggest reasons for the following features of the transition metal chemistry: 

  1. The lowest oxide of transition metal is basic, the highest is amphoteric/acidic.
  2. A transition metal exhibits highest oxidation state in oxides and fluorides.
  3. The highest oxidation state is exhibited in oxoanions of a metal.

Give one chemical test to distinguish between the following pairs of compounds. 
(i) Methylamine and dimethylamine 
(ii) Secondary and tertiary amines 
(iii) Ethylamine and aniline 
(iv) Aniline and benzylamine 
(v) Aniline and N-methylaniline

Explain briefly how +2 state becomes more and more stable in the first half of the first row transition elements with increasing atomic number?

Explain why is ortho nitrophenol more acidic than ortho methoxyphenol.

Discuss the nature of bonding in metal carbonyls
What are the different types of RNA found in the cell ?
What are interstitial compounds? Why are such compounds well known for transition metals?
The two strands in DNA are not identical but are complementary.Explain.
How do you explain the amphoteric behaviour of amino acids ?
What type of bonding helps in stabilising the ∝-helix structure of proteins ?