List of top Questions asked in CBSE Class XI

Describe the various types of placentations found in flowering plants.
Take one flower of the family Solanaceae and write its semi-technical description. Also draw their floral diagram.
What is meant by the term bond order? Calculate the bond order of: \(N_2\), \(O_2\), \(O_2^+\) and \(O_2^-\) .
Draw the labelled diagram of the following: 
(i) gram seed 
(ii) V.S. of maize seed
Bromine monochloride, BrCl decomposes into bromine and chlorine and reaches the equilibrium:
\(2BrCl (g) ⇋ Br_2 (g) + Cl_2 (g)\)
for which Kc = 32 at 500 K. If initially pure BrCl is present at a concentration of 3.3 × 10–3 mol L–1, what is its molar concentration in the mixture at equilibrium?
How useful is the study of the nature of body cavity and coelom in the classification of animals?
At 1127 K and 1 atm pressure, a gaseous mixture of CO and CO2 in equilibrium with soild carbon has 90.55% CO by mass
\(C(s) + CO_2(g) ⇋ 2CO(g)\)
Calculate Kc for this reaction at the above temperature.
How do you account for the formation of ethane during chlorination of methane?
Calculate:
  1. ∆GΘ and 
  2. the equilibrium constant for the formation of NO2 from NO and O2 at 298 K
\(NO (g) + \frac 12O_2 (g) ⇋ NO_2 (g)\)
where,
 ∆fGΘ (NO2) = 52.0 kJ/mol
∆fGΘ (NO) = 87.0 kJ/mol
∆fGΘ (O2) = 0 kJ/mol.
What are the necessary conditions for any system to be aromatic?
Does the number of moles of reaction products increase, decrease or remain same when each of the following equilibria is subjected to a decrease in pressure by increasing the volume?
  1. \(PCl_5 (g) ⇋ PCl_3 (g) + Cl_2 (g)\)
  2. \(CaO (s) + CO_2 (g) ⇋ CaCO_3 (s)\)
  3. \(3Fe (s) + 4H_2O (g) ⇋ Fe_3O_4 (s) + 4H_2 (g)\)
In the alkane \( H_3C-CH_2-C(CH_3)_2-CH_2-CH(CH_3)_2\) , identify 1°,2°,3° carbon atoms and give the number of H atoms bonded to each one of these.
What is meant by the conjugate acid-base pair? Find the conjugate acid/base for the following species: HNO2, CN– , HClO4,F–,OH–,CO and S2–
What effect does branching of an alkane chain has on its boiling point?
Which of the following are Lewis acids? H2O, BF3, H+, and NH4+.
Which of the following reactions will get affected by increasing the pressure? Also, mention whether change will cause the reaction to go into forward or backward direction.
  1. \(COCl_2 (g) ⇋ CO (g) + Cl_2 (g)\)
  2. \(CH_4 (g) + 2S_2 (g) ⇋ CS_2 (g) + 2H_2S (g)\)
  3. \(CO_2 (g) + C (s) ⇋ 2CO (g)\)
  4. \(2H_2 (g) + CO (g) ⇋ CH_3OH (g)\)
  5. \(CaCO_3 (s) ⇋ CaO (s) + CO_2 (g)\)
  6. \(4NH_3 (g) + 5O_2 (g) ⇋ 4NO (g) + 6H_2O(g)\)
Why are the classification systems changing every now and then?
Dihydrogen gas is obtained from natural gas by partial oxidation with steam as per following endothermic reaction:
\(CH_4 (g) + H_2O (g) ⇋ CO (g) + 3H_2 (g)\)
  1. Write as expression for Kp for the above reaction.
  2. How will the values of Kp and composition of equilibrium mixture be affected by
    1. increasing the pressure
    2. increasing the temperature
    3. using a catalyst?
What different criteria would you choose to classify people that you meet often?
What do we learn from identification of individuals and populations?
Explain the reason for the fusion of an organic compound with metallic sodium for testing nitrogen, sulphur and halogens.
Considering x-axis as the internuclear axis which out of the following will not form a sigma bond and why?
Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?
Name a suitable technique of separation of the components from a mixture of calcium sulphate and camphor.
Explain, why an organic liquid vaporises at a temperature below its boiling point in its steam distillation ?