Advertisements
Advertisements
प्रश्न
Aluminium dissolves in mineral acids and aqueous alkalies and thus shows amphoteric character. A piece of aluminium foil is treated with dilute hydrochloric acid or dilute sodium hydroxide solution in a test tube and on bringing a burning matchstick near the mouth of the test tube, a pop sound indicates the evolution of hydrogen gas. The same activity when performed with concentrated nitric acid, reaction doesn’t proceed. Explain the reason.
उत्तर
Al being amphoteric dissolves both in acids and alkalies evolving H2 gas which bums with a pop sound.
\[\ce{2Al + 6HCl -> 2AlCl3 + 3H2}\]
\[\ce{2Al + 2NaOH + 2H2O -> \underset{Sod meta-aluminate}{2NaAlO2} + 3H2}\]
With conic. HNO3, Al becomes passive and the reaction does not proceed. This passivity is due to the formation of a thin protective layer of its oxide (Al2O3) on the surface of the metal which prevents further action.
\[\ce{2Al + 6HNO3 -> Al2O3 + 6NO2 + 3H2O}\]
APPEARS IN
संबंधित प्रश्न
How can you explain higher stability of BCl3 as compared to TlCl3?
In some of the reactions thallium resembles aluminium, whereas in others it resembles with group I metals. Support this statement by giving some evidences.
Ionisation enthalpy (∆iH1kJ mol–1) for the elements of Group 13 follows the order.
Explain why the following compounds behave as Lewis acids?
BCl3
Match the species given in Column I with the properties mentioned in Column II.
| Column I | Column II |
| (i) \[\ce{BF^{-}4}\] | (a) Oxidation state of central atom is +4 |
| (ii) AICI3 | (b) Strong oxidising agent |
| (iii) SnO | (c) Lewis acid |
| (iv) PbO2 | (d) Can be further oxidised |
| (e) Tetrahedral shape |
Match the species given in Column I with properties given in Column II.
| Column I | Column II |
| (i) Diborane | (a) Used as a flux for soldering metals |
| (ii) Galluim | (b) Crystalline form of silica |
| (iii) Borax | (c) Banana bonds |
| (iv) Aluminosilicate | (d) Low melting, high boiling, useful for measuring high temperatures |
| (v) Quartz | (e) Used as catalyst in petrochemical industries |
Describe the general trends in the following properties of the elements in Groups 13 and 14.
Oxidation states
Three pairs of compounds are given below. Identify that compound in each of the pairs which has group 13 element in more stable oxidation state. Give reason for your choice. State the nature of bonding also.
TlCl3, TlCl
Boron fluoride exists as BF3 but boron hydride doesn’t exist as BH3. Give reason. In which form does it exist? Explain its structure.
A group 13 element ‘X’ reacts with chlorine gas to produce a compound XCl3. XCl3 is electron deficient and easily reacts with NH3 to form \[\ce{Cl3X –> NH3}\] adduct; however, XCl3 does not dimerize X is ______.
