pH

pH Scale pH is a measure of how acidic or basic a solution is. Potential for Hydrogens (H+) ranges from 0 to 14. Acidic solutions have pH < 7 pH = 7 is neutral Pure water has a pH of 7. Basic solutions: pH > 7.

pH Scale A change of 1 pH unit represents a tenfold change in the acidity of the solution. For example, if one solution has a pH of 1 and a second solution has a pH of 2, the first solution is not twice as acidic as the second—it is ten times more acidic.

pH Since the concentrations of H+ ions are small numbers expressed in scientific notation, it is easier to express the concentration using pH pH = -log [H+] Acid: pH <7 Neutral : pH = 7 Base: pH > 7

Practice Problem How would you characterize a solution of seawater that has a pH of 8?

Practice Problem If a solution has a hydrogen ion concentration of 1.0 x 10-11 M, what is the pH of the substance?

Measuring pH Litmus paper pH paper Acid-base indicators pH probe Acids cause blue litmus paper to turn red Bases cause red litmus paper to turn blue pH paper Acid-base indicators Chemical dyes whose colors are affected by acidic or basic solutions pH probe

Practice Problem A substance is tested using both red and blue litmus paper, the results are listed in the table below. Would you characterize the solution as acidic, basic or neutral? Paper type Color of paper Red litmus red Blue litmus