Advertisements
Advertisements
Question
When an alkali metal dissolves in liquid ammonia the solution can acquire different colours. Explain the reasons for this type of colour change.
Solution
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.
APPEARS IN
RELATED QUESTIONS
Why are lithium salts commonly hydrated and those of the other alkali metal ions usually anhydrous?
Write a balanced equation for the reaction between KO2 and water.
Which of the alkali metal is having least melting point?
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?
Alkali metals react with water vigorously to form hydroxides and dihydrogen. Which of the following alkali metals reacts with water least vigorously?
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 ______.
By adding gypsum to cement
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
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.
Write Lewis strucure of \[\ce{O^{-}2}\] ion and find out oxidation state of each oxygen atom? What is the average oxidation state of oxygen in this ion?
When a metal of group 1 was dissolved in liquid ammonia, the following observations were obtained:
(i) Blue solution was obtained initially.
(ii) On concentrating the solution, blue colour changed to bronze colour.
How do you account for the blue colour of the solution? Give the name of the product formed on keeping the solution for some time.
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 ______.
The metal mainly used in devising photoelectric cells is ______.
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 :
The correct order of conductivity of ions in water is ______.
