List of top Questions asked in CBSE Class XI

Consider the reactions: 
(a) \(6 \,CO_2(g) + 6H_2O(l) \rightarrow C_6H_{12}O_6(aq) + 6O_2(g)\) 
(b) \(O_3(g) + H_2O_2(l) \rightarrow  H_2O(l) + 2O_2(g)\) 
Why it is more appropriate to write these reactions as: (a) \(6\,CO_2(g) + 12H_2O(l) \rightarrow  C_6H_{12}O_6(aq) + 6H_2O(l) + 6O_2(g)\) 
(b) \(O_3(g) + H_2O_2(l) \rightarrow H_2O(l) + O_2(g) + O_2(g)\) 
Also suggest a technique to investigate the path of the above (a) and (b) redox reactions.

Which hybrid orbitals are used by carbon atoms in the following molecules? 

1. \(CH_3-CH_3\); 
2. \(CH_3-CH=CH_2\); 
3. \(CH_3-CH_2-OH\); 
4. \(CH_3-CHO\) 
5. \(CH_3COOH\)

How many electrons in an atom may have the following quantum numbers?

1. n = 4, m_s = – \(\frac 12\)
2. n = 3, l = 0

What do you understand by bond pairs and lone pairs of electrons? Illustrate by giving one example of each type.

What are hybridization states of each carbon atom in the following compounds? 
\(CH_2=C=O,\, CH_3CH=CH_2\),\((CH_3)_2CO, \,CH_2=CHCN, \,C_6H_6.\)

A certain particle carries 2.5 × 10^–16 C of static electric charge. Calculate the number of electrons present in it.

If the velocity of the electron in Bohr’s first orbit is 2.19×10⁶ms^–1, calculate the de Broglie wavelength associated with it.

Indicate the σ and π bonds in the following molecules. \(C_6H_6, C_6H_{12}, CH_2Cl_2, CH_2=C=CH_2, CH3NO2, HCONHCH_3.\)

Distinguish between a sigma and a pi bond.

Write bond line formulas for, Isopropyl alcohol, 2,3-Dimethylbutanal, Heptan-4-one.

Calculate the oxidation number of Sulphur, chromium, and nitrogen in
\(H_2SO_5\), \(Cr_2O_7^{2−}\) and \(NO_3^−\). Suggest structure of these compounds. Count for the fallacy.

Draw a neat diagram of digestive system of frog.

An ion with mass number 37 possesses one unit of negative charge. If the ion conatins 11.1% more neutrons than the electrons, find the symbol of the ion.

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

Explain the formation of \(H_2\) molecule on the basis of valence bond theory.

What is stomatal apparatus? Explain the structure of stomata with a labelled diagram.

Which of the following are isoelectronic species i.e., those having the same number of electrons?
\(Na^+, K^+, Mg^{2+}, Ca^{2+}, S^{2–}, Ar\)

Whenever a reaction between an oxidising agent and a reducing agent is carried out, a compound of lower oxidation state is formed if the reducing agent is in excess, and a compound of higher oxidation state is formed if the oxidising agent is in excess. Justify this statement giving three illustrations..

The velocity associated with a proton moving in a potential difference of 1000 V is 4.37×10⁵ ms^–1. If the hockey ball of mass 0.1 kg is moving with this velocity, calculate the wavelength associated with this velocity.

Yellow light emitted from a sodium lamp has a wavelength (λ) of 580 nm. Calculate the frequency (ν) and wavenumber (v) of the yellow light

Use molecular orbital theory to explain why the \(Be_2\) molecule does not exist.

Give the IUPAC names of the following compounds:

(f) Cl₂CHCH₂OH

Identify the substance oxidised, reduced, oxidising agent and reducing agent for each of the following reactions:

1. \(2AgBr (s) + C_6H_6O_2(aq) \rightarrow 2Ag(s) + 2HBr (aq) + C_6H_4O_2(aq)\)
2. \(HCHO(l) + 2[Ag (NH_3)_2] ^+ (aq) + 3OH^ - (aq) \rightarrow 2Ag(s) + HCOO ^- (aq) + 4NH_3(aq) + 2H_2O(l)\)
3. \(HCHO (l) + 2Cu^{ 2+}(aq) + 5 OH^ - (aq) \rightarrow Cu_2O(s) + HCOO ^- (aq) + 3H_2O(l)\)
4. \(N_2H_4(l) + 2H_2O_2(l) \rightarrow N_2(g) + 4H_2O(l)\)
5. \(Pb(s) + PbO_2(s) + 2H_2SO_4(aq) \rightarrow  2PbSO_4(s) + 2H_2O(l)\)

Cut a transverse section of young stem of a plant from your school garden and observe it under the microscope. How would you ascertain whether it is a monocot stem or a dicot stem? Give reasons.