Advertisements
Advertisements
प्रश्न
When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
Advertisements
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
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
For alkali metals, which one of the following trends is incorrect?
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?
The order of decreasing ionisation enthalpy in alkali metals is ______.
The solubility of metal halides depends on their nature, lattice enthalpy and hydration enthalpy of the individual ions. Amongst fluorides of alkali metals, the lowest solubility of LiF in water is due to ______.
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 ______.
By adding gypsum to cement
Which of the following elements does not form hydride by direct heating with dihydrogen?
Choose the correct statements from the following.
(i) Beryllium is not readily attacked by acids because of the presence of an oxide film on the surface of the metal.
(ii) Beryllium sulphate is readily soluble in water as the greater hydration enthalpy of Be2+ overcomes the lattice enthalpy factor.
(iii) Beryllium exhibits coordination number more than four.
(iv) Beryllium oxide is purely acidic in nature.
When heated in air, the alkali metals form various oxides. Mention the oxides formed by Li, Na and K.
Ions of an element of group 1 participate in the transmission of nerve signals and transport of sugars and aminoacids into cells. This element imparts yellow colour to the flame in flame test and forms an oxide and a peroxide with oxygen. Identify the element and write chemical reaction to show the formation of its peroxide. Why does the element impart colour to the flame?
The valence shell electronic configuration of alkali metals is ______.
Match List-I with List-II.
| List-I | List-II |
| (Metal) | (Application) |
| (a) Cs | (I) High temperature thermometer |
| (b) Ga | (II) Water repellent sprays |
| (c) B | (III) Photoelectric cells |
| (d) Si | (IV) Bullet proof vest |
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 ______.
The metal mainly used in devising photoelectric cells is ______.
Nitrogen combines with metals to form ______.
Given below are two statements, one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Lithium salts are hydrated.
Reason (R) : Lithium has higher polarising power than other alkali metal group members.
In the light of the above statements, choose the most appropriate answer from the options given below :
