Saved Bookmarks
| 1. |
Arrange the following in increasing order : a. First ionisation enthalpy : Mg , Al, Si, Na b. Extent of byrolysis : CCl_4 MgCl-2 , AICI_3, SiCI_4 c. Reducing power : GeCI_2_2, SnCI_2, PbCI_2 d. Oxididsing power : Gecl_4, SnCI_4, PbCi_4 e. pH of the soulution : NACl,Becl_2MgCl_2 , AlCl_3 . |
|
Answer» Solution :a. Increasing orbder of the first iobnitsation enthalypy `Na lt Al lt Mg lt Si` The valence electronic configureation of these elements are as follows : `{:[Na(Z =111 ) 3s^1],[Mg(Z= 12 ) 3s^2],[Al (Z=13) 3s^1],[Si (Z=14) 3p^2]:}` These elements belong to the same period . Aklong the period (rarr) effecitve nuclear charg increase . Hence . `IE_1` should increase as `Na lt Mg lt A llt Si` . But `Al` has lower `IE_1` value as compared to `MF` due to preneteration efect , Hence the ordr ereversea t `Al` and BECOMES : ` Na lt Al lt mg lt lSi` b. Increasing extent of hydrolysis : `C Cl_4lt MgCl_2 lt AlCl_3 lt SiCl_4` In covalent halicdes , hydroluysis occures as a reslult of corredination of a water molecule to the less eelctrongative element `C Cl_4` does not undrgo hydrolysis dut to the absiece to d-orbitals in its valence shell . So it can not expand its coordination nbumber vbeyond `4`. Thus, it cannot orrdinate with water molecules . c. Increasing reducing power : `PbCl_2 lt SnCl_2 lt GeCl_2` Amnong froup `14` elements the stability of lower oxidation states i.e `+2` increases doen the froup `(darr) ` doue to increase in INERT parie effect . d. Increasing oxidsing pwer : `GeCl_4 lt SnCl_3 lt PbCl_4` Among group `14` elements the stability of lower oxidation states i.e `+2` increases doen the group `(darr)` due to increase in inert pari effect . e. Incerasing `pH` of the solution `alCl_3 lt BeCl_2 lt mgCl_2lt NaCl` Whth increase in charge /radius ration of the central ion the tendcy to poarise eletron cloud in `H_2O` molecule and , hence dissorcattion of `O-H` bond in `H_2O` molecule increase i.e.m, more and more proton will be liberated and solution becames more actdic and `pH` DECREASES . In the compounds metioned charge /radius ration si in the order `Na^(otimes+) lt Mg^(2+) lt Al^(3+) lt Al^(3+)` and hence extent of hydrolysis follws the ordr : `NaCl lt MgCl lt BeCl_2 lt AlCl_3`Thisis why `NaCl` will be least acideic and ` AlCl_3` will be more ancidic . In other words , `pH` of `NaCl` will be least and that of `Alcl_3` will be maximum , hence the ordr : `AlCl_3 lt beCl_2 lt MgCl_2 lt NaCl`. |
|