Assume that 35.0 mL of a 0.13 M solution of a weak base B that accepts one proton is titrated with a 0.13 M solution of the monoprotic strong acid HX.

(a) How many moles of HX have been added at the equivalence point?

How many mols did you start with? That's M x L = 0.13 x 0.035 = ?

That's how many mols HX you have at the equivalence point. You didn't ask but it will take 35.0 mL of the acid to titrate the base.

To find out how many moles of HX have been added at the equivalence point, we need to determine the number of moles of the weak base B initially present and then find the moles of HX necessary to neutralize it.

First, we calculate the initial moles of the weak base B:

Moles of weak base B = volume of solution (in liters) × molarity of B

Given that the volume of the solution is 35.0 mL, we need to convert it to liters by dividing it by 1000:

Volume of solution = 35.0 mL ÷ 1000 = 0.035 L

Now we can calculate the initial moles of the weak base B:

Moles of weak base B = 0.035 L × 0.13 M = 0.00455 moles

Since we are titrating with a 0.13 M solution of the strong acid HX, at the equivalence point, the moles of HX added will be equal to the initial moles of the weak base B.

Therefore, the number of moles of HX added at the equivalence point is 0.00455 moles.