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

Among halogens, the correct order of amount of energy released in electron gain (electron gain enthalpy) is ______.

The formation of the oxide ion, \[\ce{O2- (g)}\], from oxygen atom requires first an exothermic and then an endothermic step as shown below:

\[\ce{O (g) + e- -> O- (g) ; ∆H^Θ = - 14 kJ mol^{-1}}\]

\[\ce{O- (g) + e- -> O^{2-} (g) ; ∆H^Θ = + 780 kJ mol^{-1}}\]

Thus process of formation of \[\ce{O^{2-}}\] in gas phase is unfavourable even though \[\ce{O^{2-}}\] is isoelectronic with neon. It is due to the fact that,

Which of the following elements will gain one electron more readily in comparison to other elements of their group?

(i) \[\ce{S (g)}\]

(ii) \[\ce{Na (g)}\]

(iii) \[\ce{O (g)}\]

(iv) \[\ce{Cl (g)}\]

Which of the following statements are correct?

(i) Helium has the highest first ionisation enthalpy in the periodic table.

(ii) Chlorine has less negative electron gain enthalpy than fluorine.

(iii) Mercury and bromine are liquids at room temperature.

(iv) In any period, atomic radius of alkali metal is the highest.

In which of the following options the order of arrangement does not agree with the variation of the property indicated against it?

(i) \[\ce{Al^{3+} < Mg^{2+} < Na+ < F-}\] (increasing ionic size)

(ii) \[\ce{B < C < N < O}\] (increasing first ionisation enthalpy)

(iii) \[\ce{I < Br < Cl < F}\] (increasing electron gain enthalpy)

(iv) \[\ce{Li < Na < K < Rb}\] (increasing metallic radius)

Explain why the electron gain enthalpy of fluorine is less negative than that of chlorine.

Match the correct ionisation enthalpies and electron gain enthalpies of the following elements.

Electronic configuration of some elements is given in Column I and their electron gain enthalpies are given in Column II. Match the electronic configuration with electron gain enthalpy.

Assertion (A): Boron has a smaller first ionisation enthalpy than beryllium.

Reason (R): The penetration of a 2s electron to the nucleus is more than the 2p electron hence 2p electron is more shielded by the inner core of electrons than the 2s electrons.

Assertion (A): Electron gain enthalpy becomes less negative as we go down a group.

Reason (R): Size of the atom increases on going down the group and the added electron would be farther from the nucleus.

Discuss the factors affecting electron gain enthalpy and the trend in its variation in the periodic table.

Stable form of A may be represented by the formula:

Explain the non-linear shape of \[\ce{H2S}\] and non-planar shape of \[\ce{PCl3}\] using valence shell electron pair repulsion theory.

Elements \[\ce{X, Y}\] and \[\ce{Z}\] have 4, 5 and 7 valence electrons respectively. Write the molecular formula of the compounds formed by these elements individually with hydrogen.

Elements \[\ce{X, Y}\] and \[\ce{Z}\] have 4, 5 and 7 valence electrons respectively. Which of these compounds will have the highest dipole moment?

Which of the following figures does not represent 1 mole of dioxygen gas at STP?

(i) 16 grams of gas

(ii) 22.7 litres of gas

(iii) 6.022 × 10²³ dioxygen molecules

(iv) 11.2 litres of gas

What will be the molar volume of nitrogen and argon at 273.15 K and 1 atm?

\[\ce{PCl5, PCl3 and Cl2}\] are at equilibrium at 500 K in a closed container and their concentrations are 0.8 × 10^–3 mol L^–1, 1.2 × 10^–3 mol L^–1 and 1.2 × 10^–3 mol L^–1 respectively. The value of Kc for the reaction \[\ce{PCl5 (g) ⇌ PCl3 (g) + Cl2 (g)}\] will be ______.

\[\ce{pH}\] of a solution of a strong acid is 5.0. What will be the \[\ce{pH}\] of the solution obtained after diluting the given solution a 100 times?

Calculate the \[\ce{pH}\] of a solution formed by mixing equal volumes of two solutions A and B of a strong acid having \[\ce{pH}\] = 6 and \[\ce{pH}\] = 4 respectively.