**Answer:**

To determine the pressure of hydrogen required to make the potential of the hydrogen electrode zero in pure water at 298 K, we need to consider the Nernst equation. The Nernst equation relates the potential of an electrode to the concentration of the species involved.

The Nernst equation is given as:

E = E° - (0.0592/n) * log([H+])

Where:
E = potential of the electrode
E° = standard electrode potential
n = number of electrons involved in the reaction
[H+] = concentration of hydrogen ions

In this case, we want to make the potential of the hydrogen electrode zero, so E = 0. We can rearrange the Nernst equation to solve for [H+]:

0 = E° - (0.0592/n) * log([H+])

Simplifying the equation:

E° = (0.0592/n) * log([H+])

Since we are dealing with pure water, the concentration of hydrogen ions is equal to the concentration of hydroxide ions (OH-). At 298 K, the concentration of pure water is 1.00 × 10^-7 M. Using the equation for the ion product of water, Kw = [H+][OH-], we can calculate the concentration of hydrogen ions:

[H+] = [OH-] = 1.00 × 10^-7 M

Now we can substitute the values into the equation:

0 = (0.0592/n) * log(1.00 × 10^-7)

Simplifying further:

log(1.00 × 10^-7) = -7

0 = (0.0592/n) * (-7)

0 = -0.4144/n

Since we want the potential of the hydrogen electrode to be zero, n must equal 1. Therefore, the pressure of hydrogen required can be calculated as follows:

0 = -0.4144/1

0 = -0.4144

This implies that the pressure of hydrogen required to make the potential of the hydrogen electrode zero in pure water at 298 K is 0.

Therefore, the correct answer is 0 atm.

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