Calculate the boiling point of solution when 4 gram of MgSo4 was dissolved in 100 gram of water,assuming MgSo4 goes complete ionisation.why do we use 'I' here? please answer me briefly.

Dear Student,

i is van't Hoff factor. It is used because some solutes undergo dissociation or association in soluton and such solutes have abnormal moleclar mass. Therefore, in order to know about the extent of dissociation or association of solutes in solution, van't Hoff factor is used. Now, Tb=ikbm MgSO4  Mg2+ +SO42-or, n=2and, α=i-1n-1If degree of dissociation is known, then i can be calculated and further elevation is boiling point can be calculated. Here, complete ionisation is taking place, therefore α=1or, n-1=i-1or, i=n=2m=massmolar mass×1000mass of solvent=4120×1000100=0.33kb=0.515 °Ckgmol-1So, Tb=2×0.515×0.33=0.34 and, Tb= Tb-Tb°Tb°=100°CTherefore, Tb= 100+0.34= 100.34°C  

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