List of top Questions asked in CBSE Class XI

If U = {a, b, c, d, e, f, g, h}, find the complements of the following sets:
(i) A = {a, b, c}
(ii) B = {d, e, f, g}
(iii) C = {a, c, e, g}
(iv) D = {f, g, h, a}
Consider the following species: N3- , O2-, F-, Na+, Mg2+ and Al3+ 
  1. What is common in them? 
  2. Arrange them in the order of increasing ionic radii.
Find and write down structures of 10 interesting small molecular weight biomolecules. Find if there is any industry which manufactures the compounds by isolation. Find out who are the buyers.
How many litres of water will have to be added to 1125 litres of the 45% solution of acid so that the resulting mixture will contain more than 25% but less than 30% acid content?

Find the mean and variance for the following frequency distribution.

Classes0-1010-2020-3030-4040-50
Frequencies5815166
Why did the narrator of the story want to forget the address?
Give a brief description of the principles of the following techniques taking an example in each case.(a) Crystallisation (b) Distillation (c) Chromatography.
Take one flower of the family Solanaceae and write its semi-technical description. Also draw their floral diagram.
Using s, p, d notations, describe the orbital with the following quantum numbers.
  1. n=1, l=0
  2. n = 3, l=1
  3. n = 4, l =2
  4. n=4, l=3
‘The Address’ is a story of human predicament that follows war. Comment.
‘Have you come back?’ said the woman. ‘I thought that no one had come back.’ Does this statement give some clue about the story? If yes, what is it?
Find the sum to indicated number of terms in each of the geometric progressions in 1, – a, \(a^2\), –\(a^3\), ... n terms (if a ≠ – 1).
Find n if n-1P3: nP3 = 1: 9.
Three reasons why the author’s grandmother was disturbed when he started going to the city school.
Draw diagrams showing the formation of a double bond and a triple bond between carbon atoms in \(C_2H_4\) and \(C_2H_2\) molecules.
Briefly comment on "The purpose of the author’s journey to Mount Kailash."
Justify that the following reactions are redox reactions:
  1. \(CuO(s) + H_2(g) \rightarrow Cu(s) + H_2O(g) \)
  2. \(Fe_2O_3(s) + 3CO(g) \rightarrow 2Fe(s) + 3CO_2(g) \)
  3. \(4BCl_3(g) + 3LiAlH_4(s) \rightarrow 2B_2H_6(g) + 3LiCl(s) + 3 AlCl_3 (s) \)
  4. \(2K(s) + F_2(g) \rightarrow 2K+F^- (s) \)
  5. \(4 NH_3(g) + 5 O_2(g) \rightarrow 4NO(g) + 6H_2O(g)\)
In Ostwald's process for the manufacture of nitric acid, the first step involves the oxidation of ammonia gas by oxygen gas to give nitric oxide gas and steam. What is the maximum weight of nitric oxide that can be obtained starting only with 10.00 g. of ammonia and 20.00 g of oxygen?
Find \((x + 1)^6 - (x - 1)^6\). Hence or otherwise evaluate \((\sqrt2 + 1)^6 + (\sqrt2 - 1)^6.\)
Mention the three phases of the author’s relationship with his grandmother before he left the country to study abroad.
Calculate the pH of the following solutions: 
a) 2 g of TlOH dissolved in water to give 2 litre of solution. 
b) 0.3 g of Ca(OH)2 dissolved in water to give 500 mL of solution. 
c) 0.3 g of NaOH dissolved in water to give 200 mL of solution. 
d) 1mL of 13.6 M HCl is diluted with water to give 1 litre of solution
Discuss the following statements in groups of two pairs, each pair in a group taking opposite points of view. 
i. A single event may change the course of the history of a nation. 
ii. Reality is what is directly experienced through the senses. 
iii. The methods of inquiry of history, science and philosophy are similar.
Let A = {1, 2}, B = {1, 2, 3, 4}, C = {5, 6} and D = {5, 6, 7, 8}. Verify that
  1. A x (B ∩C) = (A x B) ∩(A x C)
  2. A x C is a subset of B x D
In the organic compound \(CH_2 = CH-CH_2-CH_2-C≡CH\), the pair of hydridised orbitals involved in the formation of \(C_2 – C_3\) bond is
Draw formulas for the first five members of each homologous series beginning with the following compounds.\((a) H–COOH (b) CH_3COCH_3 (c) H–CH=CH_2\)