Question

If I am trying determine the molecular mass of an unknown acid by dissolving it in water then using standardized NaOH to titrate it with phenolphthalein, what kind of experimental modifications can be made if the acid to be titrated has low solubility in water? please explain why the modifications will work.

Answer 1

As a suggestion, you can try back titration. As it is an acidic compound it should dissolve in a basic solution like NaOH. First take a standard NaOH solution and dissolve the acidic sample in it. Calculate the amount of unreacted NaOH with a standard HCl solution. Subtract it (the amount of unreacted NaOH) from the total amount of NaOH taken initially to get the amount of NaOH equivalent to the acidic sample. Now you can do the rest of the calculations to get what you need (like molecular mass etc).