Class 11 Chemistry - Chapter The s Block Elements NCERT Solutions | Comment on each of the following observa
Comment on each of the following observations:
(a) The mobilities of the alkali metal ions in aqueous solution are Li+ < Na+ < K+ < Rb+ < Cs+
(b) Lithium is the only alkali metal to form a nitride directly.
(c) E° for M2+(aq) (where M = Ca, Sr or Ba) is nearly constant.
(a) On moving down the alkali group, the ionic and atomic sizes of the metals increase. The given alkali metal ions can be arranged in the increasing order of their ionic sizes as:
Li+ < Na+ < K+ < Rb+ < Cs+
Smaller the size of an ion, the more highly is it hydrated. Since Li+ is the smallest, it gets heavily hydrated in an aqueous solution. On the other hand, Cs+ is the largest and so it is the least hydrated. The given alkali metal ions can be arranged in the decreasing order of their hydrations as:
Li+ > Na+ > K+ > Rb+ > Cs+
Greater the mass of a hydrated ion, the lower is its ionic mobility. Therefore, hydrated Li+ is the least mobile and hydrated Cs+ is the most mobile. Thus, the given alkali metal ions can be arranged in the increasing order of their mobilities as:
Li+ < Na+ < K+ < Rb+ < Cs+
(b) Unlike the other elements of group 1, Li reacts directly with nitrogen to form lithium nitride. This is because Li+ is very small in size and so its size is the most compatible with the N3- ion. Hence, the lattice energy released is very high. This energy also overcomes the high amount of energy required for the formation of the N3- ion.
(c) Electrode potential (E°) of any M2+/M electrode depends upon three factors:
(i) Ionisation enthalpy
(ii) Enthalpy of hydration
(iii) Enthalpy of vaporisation
The combined effect of these factors is approximately the same for Ca, Sr, and Ba. Hence, their electrode potentials are nearly constant.
More Questions From Class 11 Chemistry - Chapter The s Block Elements
- Q:-
Compare the alkali metals and alkaline earth metals with respect to
(i) ionization enthalpy
(ii) basicity of oxides and
(iii) solubility of hydroxides.
- Q:-
Compare the solubility and thermal stability of the following compounds of the alkali metals with those of the alkaline earth metals.
(a) Nitrates (b) Carbonates (c) Sulphates.
- Q:-
Discuss the various reactions that occur in the Solvay process.
- Q:-
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
- Q:-
State as to why
(a) a solution of Na2CO3 is alkaline ?
(b) alkali metals are prepared by electrolysis of their fused chlorides ?
(c) sodium is found to be more useful than potassium ?
- Q:-
When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
- Q:-
In what ways lithium shows similarities to magnesium in its chemical behaviour?
- Q:-
Why is Li2CO3 decomposed at a lower temperature whereas Na2CO3 at higher temperature?
- Q:-
Find the oxidation state of sodium in Na2O2.
- Q:-
Explain why is sodium less reactive than potassium?
Popular Questions of Class 11 Chemistry
- Q:-
How do you account for the formation of ethane during chlorination of methane?
- Q:-
What are hybridisation states of each carbon atom in the following compounds ?
(i) CH2=C=O,
(ii) CH3CH=CH2,
(iii) (CH3)2CO,
(iv) CH2=CHCN,
(v) C6H6
- Q:-
What will be the minimum pressure required to compress 500 dm3 of air at 1 bar to 200 dm3 at 30°C?
- Q:-
Calculate the molecular mass of the following:
(i) H2O
(ii) CO2
(iii) CH4 - Q:-
Assign oxidation number to the underlined elements in each of the following species:
(a) NaH2PO4
(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
(e) CaO2
(f) NaBH4
(g) H2S2O7
(h) KAl(SO4)2.12 H2O
- Q:-
What is the basic theme of organisation in the periodic table?
- Q:-
Explain the formation of a chemical bond.
- Q:-
Choose the correct answer. A thermodynamic state function is a quantity
(i) used to determine heat changes
(ii) whose value is independent of path
(iii) used to determine pressure volume work
(iv) whose value depends on temperature only. - Q:-
A liquid is in equilibrium with its vapour in a sealed container at a fixed temperature. The volume of the container is suddenly increased.
a) What is the initial effect of the change on vapour pressure?
b) How do rates of evaporation and condensation change initially?
c) What happens when equilibrium is restored finally and what will be the final vapour pressure? - Q:-
Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
Recently Viewed Questions of Class 11 Chemistry
- Q:-
How many electrons in an atom may have the following quantum numbers?
(a) n = 4,
(b) n = 3, l = 0
- Q:-
What will be the mass of one 12C atom in g?
- Q:-
Indicate the number of unpaired electrons in: (a) P, (b) Si, (c) Cr, (d) Fe and (e) Kr.
- Q:-
Pressure is determined as force per unit area of the surface. The SI unit of pressure, Pascal is as shown below:
1Pa = 1N m–2
If mass of air at sea level is 1034 g cm–2, calculate the pressure in Pascal.
- Q:-
Calculate the wave number for the longest wavelength transition in the Balmer series of atomic hydrogen.
- Q:-
Calculate the energy required for the process
The ionization energy for the H atom in the ground state is 2.18 ×10–18 J atom–1
- Q:-
If the diameter of a carbon atom is 0.15 nm, calculate the number of carbon atoms which can be placed side by side in a straight line across length of scale of length 20 cm long.
- Q:-
If the velocity of the electron in Bohr’s first orbit is 2.19 × 106 ms–1, calculate the de Broglie wavelength associated with it.
- Q:-
The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electrons in 4p orbital. Which of these electron experiences the lowest effective nuclear charge?
- Q:-
34.05 mL of phosphorus vapour weighs 0.0625 g at 546 °C and 0.1 bar pressure. What is the molar mass of phosphorus?
- All Chapters Of Class 11 Chemistry
- All Subjects Of Class 11