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प्रश्न
When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
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उत्तर
When an alkali metal is dissolved in liquid ammonia, it results in the formation of a deep blue coloured solution.
\[\ce{M + (x + y) NH_3 -> M^+(NH_3)_x + e^{-1}(NH_3)_y}\]
The ammoniated electrons absorb energy corresponding to red region of visible light. Therefore, the transmitted light is blue in colour.
At a higher concentration (3 M), clusters of metal ions are formed. This causes the solution to attain a copper-bronze colour and a characteristic metallic lustre.
संबंधित प्रश्न
Explain why alkali and alkaline earth metals cannot be obtained by chemical reduction methods?
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
Which of the alkali metal is having least melting point?
Which of the following statements is incorrect?
The alkali metals are low melting. Which of the following alkali metal is expected to melt if the room temperature rises to 30°C?
Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?
The order of decreasing ionisation enthalpy in alkali metals is ______.
In the synthesis of sodium carbonate, the recovery of ammonia is done by treating NH4Cl with Ca(OH)2. The by-product obtained in this process is ______.
Metallic elements are described by their standard electrode potential, fusion enthalpy, atomic size, etc. The alkali metals are characterised by which of the following properties?
(i) High boiling point.
(ii) High negative standard electrode potential.
(iii) High density.
(iv) Large atomic size.
Which of the following compounds are readily soluble in water?
(i) BeSO4
(ii) MgSO4
(iii) BaSO4
(iv) SrSO4
When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li, Na and K.
The stability of peroxide and superoxide of alkali metals increase as we go down the group. Explain giving reason.
The valence shell electronic configuration of alkali metals is ______.
The ease of absorption of the hydrated alkali metals ions in an ion-exchange resin follows the order:
Match List-I with List-II.
| List-I | List-II |
| (Metal) | (Emitted light wavelength (nm)) |
| (a) Li | (I) 780.0 |
| (b) Na | (II) 455.5 |
| (c) Rb | (III) 670.8 |
| (d) Cs | (IV) 589.2 |
Choose the most appropriate answer from the options given below:
A white precipitate was formed when BaCl2 was added to extract of an inorganic salt. Farther, a gas 'X' with characteristic odour was released when the formed white precipitate was dissolved in dilute HCl. The anion present in the inorganic salt is ______.
Nitrogen combines with metals to form ______.
KO2 (potassium super oxide) is used in oxygen cylinders in space and submarines because it ______.
