A 0.105 L sample of an unknown HNO 3 solution required 35.7 mL of 0.250 M Ba (OH) 2 for complete neutralization. What is the concentration of the HNO 3 solution?

Answer: 0.17M

Explanation:

The equation for the reaction is:

2HNO3 + Ba (OH) 2 - > Ba (NO3) 2 + 2H2O

From the balanced equation, we obtain:

nA = mole of acid = 2

nB = mole of the base = 1

From the question, we obtain:

Va = Vol. Of acid = 0.105L

Ma = conc. Of acid = ?

Vb = Vol of base = 35.7 mL = 0.0357L

Mb = conc. of base = 0.25M.

We solve for the conc. of the acid using:

MaVa / Mb Vb = nA / nB

(Ma x 0.105) / (0.25x0.0357) = 2

Cross multiply to express in linear form. We have:

Ma x 0.105 = 0.25 x 0.0357 x 2

Divide both side by 0.105. We have

Ma = (0.25 x 0.0357 x 2) / 0.105

Ma = 0.17M

Therefore the concentration of the acid (HNO3) is 0.17M