Tuesday
May 3, 2016

# Homework Help: Chemistry

Posted by Brittany Rusk on Friday, September 22, 2006 at 5:04pm.

q1.

The label on an antacid remedy states that each tablet contains 750 mg of aluminum hydroxide. Calculate the volume of stomach acid, 0.10 mol/L HCl(aq), which can be nuetralized by one antacid tablet.

Q2.
Compare equivalence point to endpoint

q1.

The label on an antacid remedy states that each tablet contains 750 mg of aluminum hydroxide. Calculate the volume of stomach acid, 0.10 mol/L HCl(aq), which can be nuetralized by one antacid tablet.
Al(OH)3 + 3HCl ==> AlCl3 + 3H2O
The remainder of the problem is worked just like the NaOH/H2SO4 problem. Don't forget to change 750 mg to grams. I assume you know mols Al(OH)3 = g/molar mass.

Q2.
Compare equivalence point to endpoint
The equivalence point is the pH (for an acid/base titration) at which what we are titrating equals exactly the material being titrated (best stated in terms of number of equivalents but that and normality are not being taught at many schools, much to my sorrow). The end point is the pH at which an indicator TELLS us we have reached that point where the number of equivalents of acid is the same as the number of equivalents of base. That is why it is called the end point. The indicator may or may not be a good one to use and this can lead to huge errors unless we pick the right indicator. That is, we would like for the end point and the equivalence point to the be same but they rarely are. With a judicious choice of indications, however, we can make them so close in most cases that the titration error is very small. There are equivalence points and end points in other titrations as well but the same principle holds as what I have said about the pH; the difference being that we aren't titrating acid/base systems.
I hope this helps.