[hkalfighter]

i have 4 drying agents to choose , Na2SO4(s)  NaOH(s)  CaCl2(s) and P2O5(s)
what is the most suitable for drying a solution of C6H5COOH in CHCl3
My thinking > P2O5 can react with water so it's not. NaOH can react with C6H5COOH and it's not too. Then , i don't know how to make a choice with the rest . The answer is Na2SO4 but why CaCl2 is not used
also , what is the most ssuitable for drying a moist solid sample of C6H5COOH , the answer is different from that of first question ans why ?

[xiankai]

when u think about drying/dehydrating, remember that u're only trying to remove the water, hence u dont need the reagents to react, u'll want them to absorb the water instead. an ideal substance would be an anhydrous substance that is hygroscopic.

Na₂SO₄ + 10H₂O --> Na₂SO₄.10H₂O

NaOH also has a very great affinity for water, being highly deliquescent(yet another word for hygroscopic >_>)

CaCl₂  + 6H₂O --> CaCl₂.6H₂O

P2O5 is also a good dehydrating agent.

although i am not sure of which is better (2 ways exist imo, the greatest amount of water absorbed per mole or gram of molecule, or the most negative enthalpy of dissolution)

thats all i know on the subject matter, maybe someone else can elaborate

[AWK]

NaOH and P2O5 can react, CaCl2 ans Na2SO4 are rather poor drying agents, though cheap, CaCl2 works much faster..
I advice anhydrous CaSO4, MgSO4 or dried molecular sieves for your mixture.

[hkalfighter]

thx , the solution states that CaCl2 can't be used because it reacts with organic compounds with oxygen or nitrogen , forming complex , why ? it states with further explanation