Under what conditions will CuSO_4.5H_2O be efflorescent at 25^(@)C? For the reaction CuSO_4.5H_2O_((s)) harr CuSO_4.3H_2O_((s))+2H_2O_((g)) K_p at 298K is 1086 xx 10^(-4) atm^2 and vapour pressure of water is 23.8 Torr.

Under what conditions will CuSO_4.5H_2O be efflorescent at 25^(@)C? Fo

1.	Under what conditions will CuSO_4.5H_2O be efflorescent at 25^(@)C? For the reaction CuSO_4.5H_2O_((s)) harr CuSO_4.3H_2O_((s))+2H_2O_((g)) K_p at 298K is 1086 xx 10^(-4) atm^2 and vapour pressure of water is 23.8 Torr.
Answer» If relative HUMIDITY `LT` 33.3%, efflorescence takes place If relative humidity `gt` 33.3%, efflorescence takes place The salt does not act as efflorescent at `25^(@)C` The salt effloreses if the vapour pressure of water vapour in atmosphere `lt` 7.92 mm. Solution :`CuSO_(4).H_(2)O_((s)) harr CUSO_(4).3H_(2)O_((s))+2H_(2)O_((G))` `K_(P)=P_(H_(2)O)^(2) implies P_(H_(2)O) = sqrt(K_(P))=7.92` mm Relative humidity = `(P_(H_(2)O))/("vapour pressure of" H_(2)O)` `=(7.92)/(23.8)=0.333` % R.H=33.3 `Q lt K`, forward direction The reaction will PROCEED only when vapour pressure of moisture in atmosphere is lesser than 7.92mm to show efflorescent nature.