Question

why is pH scale is more used than pOH scale and is also more popular though they are the same?

Answer 1

Both scales provide a measure of either the H+ concentration or the OH- concentration. Notice that each scale shows were acids and bases both are located. When acids are measured, the pH is less than 7, but the pOH is greater than 7. When bases are measured, the pH is greater than 7, but the pOH is less than 7.