The concentration of an unknown acid solution with general formula H3A is to be determined by titration with a 0.850 M KOH solution. Determine the concentration of the acid solution given that 38.34 mL of KOH solution were needed to fully neutralize 15.00 mL of the acid solution.

0.7242 M

Explanation:

Step 1:

Data obtained from the question. This include the following:

Molarity of base, KOH (Mb) = 0.850 M

Volume of base, KOH (Vb) = 38.34 mL

Volume of acid, H3A (Va) = 15.00 mL

Molarity of acid, H3A (Ma) = ... ?

Step 2:

The balanced equation for the reaction. This is given below:

H3A + 3KOH - > K3A + 3H2O

From the balanced equation above,

The mole ratio of the acid, H3A (nA) = 1

The mole ratio of the base, KOH (nB) = 3

Step 3:

Determination of the concentration of the acid, H3A.

The concentration of the acid, H3A can be obtained as follow:

MaVa / MbVb = nA/nB

Ma x 15 / 0.850 x 38.34 = 1/3

Cross multiply

Ma x 15 x 3 = 0.850 x 38.34

Divide both side by 15 x 3

Ma = (0.850 x 38.34) / (15 x 3)

Ma = 0.7242 M

Therefore, the concentration of acid, H3A is 0.7242 M