Class 11 Chemistry - Chapter The s Block Elements NCERT Solutions | State as to why (a) a solution of Na2
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 ?
(a) When sodium carbonate is added to water, it hydrolyses to give sodium bicarbonate and sodium hydroxide (a strong base). As a result, the solution becomes alkaline.
Na2CO3 + H2O → NaHCO3 + NaOH
(b) It is not possible to prepare alkali metals by the chemical reduction of their oxides as they themselves are very strong reducing agents. They cannot be prepared by displacement reactions either (wherein one element is displaced by another). This is because these elements are highly electropositive. Neither can electrolysis of aqueous solutions be used to extract these elements. This is because the liberated metals react with water.
Hence, to overcome these difficulties, alkali metals are usually prepared by the electrolysis of their fused chlorides.
(c) Blood plasma and the interstitial fluids surrounding the cells are the regions where sodium ions are primarily found. Potassium ions are located within the cell fluids. Sodium ions are involved in the transmission of nerve signals, in regulating the flow of water across the cell membranes, and in transporting sugars and amino acids into the cells. Hence, sodium is found to be more useful than potassium.
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:-
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.
- Q:-
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
- 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:-
Why is Li2CO3 decomposed at a lower temperature whereas Na2CO3 at higher temperature?
- Q:-
In what ways lithium shows similarities to magnesium in its chemical behaviour?
- Q:-
Find the oxidation state of sodium in Na2O2.
- Q:-
Explain why is sodium less reactive than potassium?
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- Q:-
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- Q:-
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- Q:-
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(iii) CH4 - Q:-
Assign oxidation number to the underlined elements in each of the following species:
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(b) NaHSO4
(c) H4P2O7
(d) K2MnO4
(e) CaO2
(f) NaBH4
(g) H2S2O7
(h) KAl(SO4)2.12 H2O
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- 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.
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- Q:-
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(a)
(b)
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- Q:-
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2 S2O2– 3 (aq) + I2(s) → S4 O2– 6(aq) + 2I – (aq)
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