Science (English Medium) कक्षा ११ - CBSE Question Bank Solutions

Define ionisation enthalpy. Discuss the factors affecting ionisation enthalpy of the elements and its trends in the periodic table.

Discuss and compare the trend in ionisation enthalpy of the elements of group1 with those of group17 elements.

Polarity in a molecule and hence the dipole moment depends primarily on electronegativity of the constituent atoms and shape of a molecule. Which of the following has the highest dipole moment?

Arrange the following bonds in order of increasing ionic character giving reason.

\[\ce{N - H, F - H, C - H}\] and \[\ce{O - H}\]

18.0 g of water completely vapourises at 100°C and 1 bar pressure and the enthalpy change in the process is 40.79 kJ mol–1. What will be the enthalpy change for vapourising two moles of water under the same conditions? What is the standard enthalphy of vapourisation for water?

The value of ∆_fH^Θ for \[\ce{NH3}\] is – 91.8 kJ mol^–1. Calculate enthalpy change for the following reaction:

\[\ce{2NH3(g) -> N2(g) + 3H2(g)}\]

Which of the following options will be correct for the stage of half completion of the reaction A ⇌ B.

For the reaction \[\ce{N2O4 (g) ⇌ 2NO2 (g)}\], the value of K is 50 at 400 K and 1700 at 500 K. Which of the following options is correct?

(i) The reaction is endothermic.

(ii) The reaction is exothermic.

T

(iv) The entropy of the system increases.

The value of \[\ce{K_c}\] for the reaction \[\ce{2HI (g) ⇌ H2 (g) + I2 (g)}\] is 1 × 10^–4 At a given time, the composition of reaction mixture is \[\ce{[HI]}\] = 2 × 10^–5 mol, \[\ce{[HI]}\] = 1 × 10^–5 mol and \[\ce{[I2]}\] = 1 × 10^–5 mol In which direction will the reaction proceed?

Following data is given for the reaction: \[\ce{CaCO3 (S) -> CaO (s) + CO2 (g)}\]

\[\ce{∆_fH^Θ [CaO(s)] = - 635.1 kJ mo^{-1}}\]

\[\ce{∆_fH^Θ [CO2(g)] = - 393.5 kJ mol^{-1}}\]

\[\ce{∆_fH^Θ [CaCO3(s)] = - 1206.9 kJ mol^{-1}}\]

Predict the effect of temperature on the equilibrium constant of the above reaction.

How can you predict the following stages of a reaction by comparing the value of K_c and Q_c?

(i) Net reaction proceeds in the forward direction.

(ii) Net reaction proceeds in the backward direction.

(iii) No net reaction occurs.

Identify the correct resonance structures of carbon dioxide from the ones given below:

(i) O – C ≡ O

(ii) O = C = O

(iii) ^–O ≡ C – O⁺

(iv) ^–O – C ≡ O⁺

What is the significance of the terms - ‘isolated gaseous atom’ and ‘ground state’ while defining the ionization enthalpy and electron gain enthalpy?

Hint: Requirements for comparison purposes.

Which of the following pair of elements would have a more negative electron gain enthalpy?

F or Cl

Would you expect the second electron gain enthalpy of O as positive, more negative or less negative than the first? Justify your answer.

Describe the theory associated with the radius of an atom as it gains an electron.

Describe the theory associated with the radius of an atom as it loses an electron.

Discuss the shape of the following molecules using the VSEPR model:

BeCl₂, BCl₃, SiCl₄, AsF₅, H₂S, PH₃

Although geometries of NH₃ and H₂O molecules are distorted tetrahedral, bond angle in water is less than that of ammonia. Discuss.

Calculate the total number of electrons present in 1.4 g of dinitrogen gas.