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11.24     How would you explain the lower atomic radius of Ga as compared to Al ?

The atomic radius of the gallium is less than the atomic radius of aluminium. This is because of the weak shielding effect of the 3d electron of gallium. The shielding effect of d-electrons are feeble so that the effective nuclear charge experienced by the valence electron in  is quite higher than the 

11.23     Explain why is there a phenomenal decrease in ionization enthalpy from carbon to silicon ?

Ionisation enthalpy of carbon is quite high because it is small in size. However, on going down the group to silicon, there is a sudden decrease in the enthalpy of the silicon. This is due to the large increase in the atomic size of the silicon element.

11.10     Write the resonance structures of CO_{3}^{2-}and HCO_{3}^{-}.

The resonance structure of the  and -  

11.9     What are electron deficient compounds ? Are BCl_{3} and SiCl_{4} electron deficient species ? Explain.

Electron-deficient compounds are those in which the octet of the central atom is not completed. Therefore, the metal wants to complete its octet by accepting an electron from a donor molecule.  is an electron-deficient compound because of the central atom, Boron has only 6 electrons, two electrons are needed to complete its octet.  silicon has 4 valence electrons and by covalent bonding, it...

11.8     Write reactions to justify amphoteric nature of aluminium.

amphoteric nature of aluminium means it shows properties of acid as well as the base. Aluminium dissolves in acid and bases. Reaction with acids- Reaction with the base-

11.7     Describe the shapes of BF_{3} and BH_{4}^{-}. Assign the hybridisation of boron in these species.

The hybridisation of Boron in  and is  and  respectively.

11.6     Explain what happens when boric acid is heated.

On heating boric acid around 370 K, it converts to metaboric acid(  ). If we continue the heating process, it becomes boric oxide.  

11.5     Is boric acid a protic acid ? Explain.

Boric acid is not a protic acid. It is a weak monobasic acid, behaves as a Lewis acid by accepting a pair of an electron from the water molecules()

11.4     Consider the compounds, BCl_{3}  and CCl_{4}. How will they behave with water ? Justify.

 is a Lewis acid, it is an electron deficient molecules. So, it readily undergoes to hydrolysis. On hydrolysis gives boric acid.  does not undergo hydrolysis because carbon has no vacant orbital, so it cannot accept an electron from the water molecule to form intermediate.   + water no reaction

11.22.    Give reasons :

  (vii)  Aluminium wire is used to make transmission cables.

Aluminium wires are good conductors of electricity and also it is cheap metal easily available, light in weight and also very good ductility. All these properties of aluminium make it better to make transmission cables.

11.22.    Give reasons :

  (vi)  Aluminium utensils should not be kept in water overnight.

Aluminium utensils should not be kept in water overnight because it reacts with water with the help of atmospheric oxygen and forms an oxide layer on the surface of utensils. When we kept water on this utensils for a long period of time, some amount of oxide dissolved in water which is harmful(water become basic in nature). 

11.22.    Give reasons :

 (v) Aluminium alloys are used to make aircraft body.

Aluminium has very good tensile strength and is very light in weight also. It can be alloyed with the various metals such as copper, manganese and Silicon etc. Al is malleable and ductile. Because of these properties of Aluminium, it can be used in making aircrafts bodies.

11.22.    Give reasons :

(iv) Diamond is used as an abrasive.

The carbons of the diamond are in  hybridisation. Each carbon is attached with the four neighbour carbon atom by a strong covalent bond. This covalent bond gives the diamond a very rigid structure and it is very difficult to break this covalent bond and due to this reason it is the hardest substance and used as an abrasive

11.22.    Give reasons :

   (iii)  Graphite is used as lubricant.

Graphite has a layered structure and each layer is bonded by the weak van der Waals forces. These layers can slide over each other that's why graphite can be used as a lubricant.

11.22.    Give reasons :

  (ii) A mixture of dilute N\! aO\! H and aluminium pieces is used to open drain.

When the mixture of dilute and aluminium pieces reacts, they formed sodium tetrahydroxy aluminate (III)and dihydrogen gas. To open the drains, we use the pressure produced by the hydrogen gas.

11.22.    Give reasons

  (i)  Conc. H\! N\! O_{3}  can be transported in aluminium container.

Conc.   can be transported in an aluminium container because when it reacts with the aluminium it forms a thin layer of oxide on the surface. This layer renders aluminium passive.  

11.21.    Explain the following reactions

 (d) Hydrated alumina is treated with aqueous N\! aO\! \! \, H solution;

Hydrated alumina is treated with an aqueous solution leads to the formation of sodium meta aluminate  

11.21.    Explain the following reactions

  (c) CO is heated with Z\! nO;

When CO reacts with , it acts as a reducing agent and reduces the  to zinc.

11.21.    Explain the following reactions

 (b) Silicon dioxide is treated with hydrogen fluoride;

When Silicon dioxide is treated with hydrogen fluoride, it forms silicon tetrafluoride and  further reacts with the HF to form hydrofluorosilic acid. ???????

11.21.    Explain the following reactions
  (a) Silicon is heated with methyl chloride at high temperature in the presence of copper;

Silicon is heated with methyl chloride at high temperature in the presence of copper; as a catalyst at a temperature around 573K different types of methyl substituted chlorosilane are formed. for example- and a small amount of 
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