Strong bases and strong acids completly dissociate in solution. In the tiltratio

Question

Strong bases and strong acids completly dissociate in solution. In the tiltration of strong acids and bases the following neutralizacion reaction occurs : H+ + OH- -> H20. Nitric acid and sodium hydroxide are a strong acid and strong base.

1) A solution containing nitric acid (HNO3) is to be used in the neutralization titration of a (NaOH) solution . If the pH of nitric acid solution is 2.70, what is the normality of the nitric acid??

2) If 40.00 mL of this nitric acid solution are required to neutrilize 90.00mL of NaOH solution, what is the normality of the NaOH solution?

3) What was the pH of the NaOH solution before neutralization?

Explanation / Answer

1)

pH = -log [H+]

2.70 = -log [H+]

[H+] = 1.995 x 10^-3 M

The dissociation reaction of HNO3 is

HNO3 ----> H+ + NO3^-

Normality is calculated as # of equivalents of HNO3/ L of solution

# of equivalents = # of moles/ # of H+ ions released upon dissociation

in case of HNO3, only 1 mol H+ ions are released by 1 mol HNO3

So we an assume that # of equivalents = # of moles

So, normality = molarity

HNO3 being a strong acid, we can assume that [H+] = [HNO3]

[HNO3] = 1.995 x 10^-3 mol/L = 0.00199 M

Since in case of HNO3 molarity is equal to normality

Normality of HNO3 = 0.00199 N

2)

We can use the formula N1V1 = N2V2

0.00199 N x 40.00 mL = N2 x 90.00mL

N2 = 0.000884 N

3)

Fo NaOH normality is equal to molarity

So M = 0.000884 mol/L

NaOH is a strong base, there OH- concentration would be same as [NaOH]

[OH-] = 0.000884 M

pOH = - log (0.000884) = 3.05

but pH + pOH = 14

So, pH = 14 - 3.05 = 10.95

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