Question

20.0 mL of 0.100 M nitric acid is titrated with 0.0500 M barium hydroxide at 10°C. Write the net ionic equation for the titration reaction and calculate the pH at the equivalence point. Kw = 2.5 * 10-15 at 10°C.

Answer 1

The net ionic equation for the titration with nitric acid and barium hydroxide is HNO3 + OH- → H2O + NO3-. At the equivalence point, the pH is calculated to be about 7.30, using the ionic product of water at 10°C.

Step-by-step explanation:

The net ionic equation for the titration of 20.0 mL of 0.100 M nitric acid (HNO3) with 0.0500 M barium hydroxide (Ba(OH)2) at 10°C is as follows:

HNO3(aq) + OH−(aq) → H2O(l) + NO3−(aq)
To calculate the pH at the equivalence point, we must consider the reaction of barium nitrate produced at this point. Barium nitrate is a salt resulting from a strong acid and strong base, so it will not affect the pH. The pH is determined by the water dissociation Kw at 10°C, which is given as 2.5 × 10−15. Since at the equivalence point the concentrations of H+ and OH− are equal, we find the concentration of H+ by taking the square root of Kw:
[H+] = √Kw = √(2.5 × 10−15)
This gives us [H+] = 5.0 × 10−8 M. Using the pH formula:

pH = −log[H+]
The pH calculation results in approximately 7.30 at the equivalence point. This more basic pH, compared to room temperature, is due to the temperature dependent increase of Kw.