[cuongt]

why is aspirin insoluble in water? is it because it only has one OH bond(hydorgen bond) and also its structure is a large non polar component?
and when NaHCO3 is added why does it make aspirin soluble in water?( this i dont get  )

[Yggdrasil]

Yes, since most of aspirin is non-polar, it is insoluble in water.

For your second question, think about how sodium bicarbonate reacts with asprinin (hint: aspirin = acetylsalicylic acid) and how this changes the properties of aspirin to make it more soluble.

[cuongt]

TY TY TY ROFL 

[Albert]

For your second question, think about how sodium bicarbonate reacts with aspirin (hint: aspirin = acetylsalicylic acid) and how this changes the properties of aspirin to make it more soluble.

NaHCO3 reduces disaggregation time due to effervescence. The reaction between NaHCO3 and acetylsalicylic acid yields H2CO3 (hence, H2O + CO2). The bubbles act like an explosive.

[Yggdrasil]

However, powdered acetylsalicylic acid is still going to be largely insoluble in water.  The main purpose of the sodium bicarbonate is to deprotonate the carboxylic acid in acetylsalicylic acid to produce a sodium acetylsalicylate salt which is much more soluble in water (due to the presence of a charged carboxylate group).  The effervesence, as Albert noted, will help the sodium acetlysalicylate disolve faster.

[cuongt]

wow soo much depth thanx for explanation and help guys 

[TheMantis]

Actually, Aspirin is partially soluble in water.  The reason why it is only partially soluble in water is because of its hydrophobic portion of the molecule.  Also, the hydrogen on the carboxylic acid functional group can hydrogen bond with the oxygen atom of the ester carbonyl group making it even further less soluble in water.

When you treat aspirin with sodium bicarbonate, it undergoes an acid base reaction to give you a sodium carboxylate, which is an ionic species of aspirin, thus making it water soluble.  Also, the intermolecular hydrogen bonding affect is now absent because the proton on the carboxylic acid is now gone.