Suppose you are titrating an acid solution with a base solution of known concentration. To calculate the concentration of the acid solution, use three steps. 1. Use the choose. Of base choose. The endpoint and the known concentration of the base solution to find the choose. Of base used. 2. Use the choose. To find the moles of acid from the moles of base. 3. Divide the moles of acid by the volume of choose. The titration to find the concentration of acid.