Answer:
3.98 ×10-6 mol dm-3
Explanation:
The pH is defined as the negative logarithm of hydrogen ion concentration to base ten. This implies that when we want to obtain the concentration of hydrogen ion in moldm-3 and all we have is the pH of the solution, we simply take the antilog of the negative value of the given pH value. This follows from the definition of pH above. All these steps are shown in the image attached.