Class 11 Chemistry - Chapter The s Block Elements NCERT Solutions | How would you explain the following obse

Compare the alkali metals and alkaline earth metals with respect to

(i) ionization enthalpy

(ii) basicity of oxides and

(iii) solubility of hydroxides.

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.

Discuss the various reactions that occur in the Solvay process.

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.

Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?

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 ?

When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.

In what ways lithium shows similarities to magnesium in its chemical behaviour?

Why is Li₂CO₃ decomposed at a lower temperature whereas Na₂CO₃ at higher temperature?

Find the oxidation state of sodium in Na₂O₂.

How do you account for the formation of ethane during chlorination of methane?

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

What will be the minimum pressure required to compress 500 dm³ of air at 1 bar to 200 dm³ at 30°C?

Calculate the molecular mass of the following:
(i) H₂O
(ii) CO₂
(iii) CH₄

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

What is the basic theme of organisation in the periodic table?

Explain the formation of a chemical bond.

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.

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?

Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.

Explain the difference in properties of diamond and graphite on the basis of their structures.

Which one of the following statements is incorrect in relation to ionization enthalpy?
(a) Ionization enthalpy increases for each successive electron.
(b) The greatest increase in ionization enthalpy is experienced on removal of electron from core noble gas configuration.
(c) End of valence electrons is marked by a big jump in ionization enthalpy.
(d) Removal of electron from orbitals bearing lower n value is easier than from orbital having higher n value.

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.

Which of the following pairs of elements would have a more negative electron gain enthalpy?
(i) O or F
(ii) F or Cl

A welding fuel gas contains carbon and hydrogen only. Burning a small sample of it in oxygen gives 3.38 g carbon dioxide, 0.690 g of water and no other products. A volume of 10.0 L (measured at STP) of this welding gas is found to weigh 11.6 g. Calculate

(i) empirical formula,

(ii) molar mass of the gas, and

(iii) molecular formula.

Calculate the wavelength, frequency and wave number of a light wave whose period is 2.0 × 10^–10 s.

Describe the shapes of BF₃ and  BH₄^-. Assign the hybridisation of boron in these species.

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength 6800 Å. Calculate threshold frequency (v₀) and work function (W₀) of the metal.

Use Lewis symbols to show electron transfer between the following atoms to form cations and anions:

(a) K and S (b) Ca and O (c) Al and N.

For the following equilibrium, K_c = 6.3 × 10¹⁴  at 1000 K

NO (g) + O₃ (g) ↔ NO₂ (g) + O₂ (g)

Both the forward and reverse reactions in the equilibrium are elementary bimolecular reactions. What is K_c, for the reverse reaction?