List of top Questions asked in CBSE Class XI

If the photon of the wavelength 150 pm strikes an atom and one of its inner bound electrons is ejected out with a velocity of 1.5 × 10⁷ ms^–1, calculate the energy with which it is bound to the nucleus.

A sample of HI(g) is placed in flask at a pressure of 0.2 atm. At equilibrium the partial pressure of HI(g) is 0.04 atm. What is K_p for the given equilibrium ?
\(2HI (g) ⇋ H_2 (g) + I_2 (g)\)

Write the significance of a plus and a minus sign shown in representing the orbitals.

Write the important conditions required for the linear combination of atomic orbitals to form molecular orbitals.

Distinguish anaphase of mitosis from anaphase I of meiosis.

The following results are observed when sodium metal is irradiated with different wavelengths. Calculate (a) threshold wavelength and, (b) Planck’s constant

What is meant by hybridisation of atomic orbitals? Describe the shapes of \(sp, sp ^2 , sp ^3\) hybrid orbitals.

At \(450\ K\), \(K_p= 2.0 × 10^{10}/bar\) for the given reaction at equilibrium.
\(2SO_2(g) + O_2(g) ⇋ 2SO_3 (g)\)
What is \(K_c\) at this temperature ?

Which out of NH₃ and NF₃ has higher dipole moment and why?

Differentiate between:
(a) Respiration and Combustion 
(b) Glycolysis and Krebs’ cycle 
(c) Aerobic respiration and Fermentation

The work function for caesium atom is 1.9 eV. Calculate (a) the threshold wavelength and (b) the threshold frequency of the radiation. If the caesium element is irradiated with a wavelength 500 nm, calculate the kinetic energy and the velocity of the ejected photoelectron.

The longest wavelength doublet absorption transition is observed at 589 and 589.6 nm. Calculate the frequency of each transition and energy difference between two excited states.

Write Lewis dot symbols for atoms of the following elements: Mg, Na, B, O, N, Br.

In astronomical observations, signals observed from the distant stars are generally weak. If the photon detector receives a total of 3.15 × 10^–18 J from the radiations of 600 nm, calculate the number of photons received by the detector.

Give the schematic representation of glycolysis?

Explain why pure liquids and solids can be ignored while writing the equilibrium constant expression?

Give the schematic representation of an overall view of Krebs’ cycle.

For the following equilibrium, \(K_c = 6.3 × 10^{14}\) at \(1000\  K\)
\(NO (g) + O_3 (g) ⇋ NO_2 (g) + O_2 (g)\)
Both the forward and reverse reactions in the equilibrium are elementary bimolecular reactions. What is \(K'_c\) for the reverse reaction?

Explain ETS.

The skeletal structure of CH₃COOH as shown below is correct, but some of the bonds are shown incorrectly. Write the correct Lewis structure for acetic acid.

Explain the process of inspiration under normal conditions.

Arrange the bonds in order of increasing ionic character in the molecules: LiF, K₂O, N₂, SO₂ and ClF₃.

Define electronegativity. How does it differ from electron gain enthalpy?

Write the expression for the equilibrium constant, K_c for each of the following reactions: 

1. \(2NOCl (g) ⇋ 2NO (g) + Cl_2 (g)\)
2. \(2Cu(NO_3)_2 (s) ⇋ 2CuO (s) + 4NO_2 (g) + O_2 (g)\)
3. \(CH_3COOC_2H_5(aq) + H_2O(l) ⇋ CH_3COOH (aq) + C_2H_5OH (aq)\)
4. \(Fe^{3+} (aq) + 3OH^– (aq) ⇋ Fe(OH)_3 (s)\)
5. \(I_2 (s) + 5F_2 ⇋ 2IF_5\)

Write the significance/applications of dipole moment.