Answer:
As you move towards the left on the pH scale, the acidity of the solution increases, meaning that the concentration of H+ ions increases and the concentration of OH- ions decreases.
At pH 7 (neutral), the concentration of H+ and OH- ions is equal at 10^-7 moles per liter. As the pH decreases below 7, the concentration of H+ ions increases, and the concentration of OH- ions decreases accordingly. For example, at pH 4, the concentration of H+ ions is 10^-4 moles per liter, while the concentration of OH- ions is 10^-10 moles per liter.
Conversely, as you move towards the right on the pH scale, the acidity decreases, the concentration of H+ ions decreases, and the concentration of OH- ions increases. For example, at pH 10, the concentration of H+ ions is 10^-10 moles per liter, while the concentration of OH- ions is 10^-4 moles per liter.
In summary, as you proceed to the left on the pH scale, the H+ ion concentration increases, and the OH- ion concentration decreases, while the opposite occurs as you move towards the right on the pH scale.