Science (English Medium) Class 11 - CBSE Question Bank Solutions for Chemistry

Those elements impart colour to the flame on heating in it, the atoms of which require low energy for the ionisation (i.e., absorb energy in the visible region of spectrum). The elements of which of the following groups will impart colour to the flame?

(i) 2

(ii) 13

(iii) 1

(iv) 17

Among the elements \[\ce{B, Al, C}\] and \[\ce{Si}\], which element has the highest first ionisation enthalpy? 

Nitrogen has positive electron gain enthalpy whereas oxygen has negative. However, oxygen has lower ionisation enthalpy than nitrogen. Explain.

Arrange the elements \[\ce{N, P, O}\] and \[\ce{S}\] in the order of increasing first ionisation enthalpy. Give reason for the arrangement assigned.

Explain the deviation in ionisation enthalpy of some elements from the general trend by using the given figure.

Explain the following:

Ionisation enthalpy decrease in a group from top to bottom?

Assertion (A): Generally, ionisation enthalpy increases from left to right in a period.

Reason (R): When successive electrons are added to the orbitals in the same principal quantum level, the shielding effect of inner core of electrons does not increase very much to compensate for the increased attraction of the electron to the nucleus.

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.