What is pH?

Water In a sample of water, a small amount of the water ionizes into H+ and OH- H2O → H+ + OH- The more H+ is in a sample, the more acidic it is The amounts of h+ and OH- ions are very small Neutral H+ = 1 x 10-7 Acidic H+ = 1 x 10-3 Basic H+ = 1 x 10-12

Calculating ph These small numbers in scientific notation are difficult to work with Shorthand way to represent these numbers is with a log scale pH = - log [ h+ ] logs show the exponent of the base 10 ph = - log ( 1 x 10-4) = 4

The pH Scale Each pH unit is 10 times as large as the previous one A change of 2 pH units means 100 times more basic or acidic x10 x100

The pH Scale Careful measurement is important A mistake of one pH unit means 10 times too much or too little! x10 x100

To Use pH Paper Place the edge of the pH paper into the mixture. Observe the color change of the pH paper Match the resulting color to the colors listed on the outside of the pH paper package. The colors match with a correlated pH number. The number is the pH value of the sample.