Calculate the amount of Tris(hydroxlmethyl)aminomethane(Tris) necessary to make 100mL of a 0.100 M Tris buffer that is equimolar in Tris-base (MW=121.1 g/mol) and Tris-HCL (MW= 157.6g/mol)

Answer 1

Let's see.
M = mols/L; therefore,
# mols = M x L
You have M = 0.100 and you have L - 0.100 so you want 0.01 mols of the base and 0.01 mols of the salt (the acid) (since the problem states you want an equimolar solution of base and acid.
After you know mols, then mols = grams/molar mass. You know molar mass and you know the mols, calculate grams of the base and grams of the salt (acid). Voila!

Answer 2

But then if they ask us to predict the pH of this solution, using the Handerson-Haselbach equation...?