Chapter 19 Outline to Prentice Hall's Chemistry - Connections to Our Changing World.
...proposed a more compact way to Express the concentrations of H3O+ ions. - His scale is based on logarithms and is known as the pH scale. - A number’s base 10 logarithm is its exponent when 10 is the base. For example, 10,000 is the same as 10^4, so log(10,000) is 4. - In calculating pH, keep significant digits in mind. For any logarithm, the number of digits after the decimal point should equal the number of sig. digs. in the original no. - For example, consider the logarithm of 8.7 x 10-4. Your calculator will Probably provide a logarithm with many digits after the decimal. However 8.7 x 10-4 only has 2 sig digs, so its logarithm should be rounded off at the second digit past the decimal point. - There are two common ways to measure the pH of a solution. - The simplest way is to use and acid-base indicator. - Indicators are weak acids or bases that undergo a color change when they gain or lose and H+ ion. - A second and more accurate way to measure pH is to use a device called a pH meter. 19-2 Buffers - In many solutions, like solutions found in living things, the pH must be controlled within very narrow limits. - The human body must maintain the pH of blood between 7.35 and 7.45. - A way to control the pH of a solution is with a buffer. - A buffer is a mixture that is able to release or absorb H+ ions, keeping a solution’s pH constant. - The amount of acid or base a buffer can neutralize is called the buffer capacity. - In general, the greater the concentration of buffer, the greater the buffer capacity. 19-3 Acid-Base Titration - An acid-base titration is used to calculate the concentration of acid or base in a solution. - A carefully controlled neutralization reaction is called an acid-base titration. - To run a titration on a solution of unknown concentration...