Acids, Bases, and pHChapter 2

Concentration # of grams of solute

# of Liters of solutionUnits is grams per Liter g/LThe bigger the #, the more concentrated, the

smaller the #, the more diluteRuben dissolves 18 grams of sugar in a 2

liter bottle of water. What is the concentration of his sugar water?18 grams sugar/2 Liters of water= 9 g/L

David dissolves 36 grams of sugar in a big 6 liter bottle of water. What is the concentration of his sugar water?36 grams of sugar/6 Liters of water=6 g/L

Whose sugar water is more concentrated?Ruben’s is more concentrated

Acids and basesA water molecule can react to form ions

What is an ion? An atom or molecule that has lost or gained an e- and

therefore is CHARGED (+ or -)H2O H+ + OH- Water Hydrogen ion Hydroxide ion

In pure water, this happens to every 1 water molecule in 550 million

Water in NEUTRAL (no charge) because # of H+ (hydrogen) ions = # of OH-

(hydroxide) ions [H+] = [OH-]

pH scaleThe scale we use to measure the # of H+ (hydrogen) ions in water…we

call this the “concentration” of H+ ions The scale goes from 0 to 14

0 is VERY ACIDIC 14 is VERY basic 7 is NEUTRAL (water)

Acids and bases are SOLUTIONS…they are compounds dissolved in waterAcid

Any compound that releases/produces H+ ions in water INCREASE concentration of H+ ions in water pH value BELOW 7 Strong acids range from 0 to 3

Base Any compound that releases/produces OH- ions in water The OH- ions snatch up any available H+ ions already in the water,

therefore… DECREASES concentration of H+ ions in water pH value ABOVE 7 Strong bases range from 11 to 14

http://www3.oes.edu/ms/science6/Pictures%20of%20Science%20Concepts/pH%20Scale.gif

BufferspH of most cells in body is kept between 6.5

and 7.5Enzymes can only function at these pH levels

What is an enzyme?A protein that speeds up the rate of a reaction

in living things by lowering the activation EControlling pH is important in homeostasis

What is homeostasis? Maintaining a stable internal environment

Buffers help maintain a stable pH so cells can function and the necessary chemical reactions can take place

Buffers continued…Buffer

A weak acid added to a strong base OR a weak base added to a strong acid…

That help bring the pH of that strong acid/base closer to seven

Prevents sharp changes in pH (that’s why we use weak acids and bases as buffers)

Limestone is a weak baseVinegar (acetic acid) is a weak acidHeartburn…what do you do?

Acid PrecipitationAcid precipitation refers to rain, snow, or fog

with a pH lower than 5.6Acid precipitation is caused mainly by the mixing

of different pollutants with water in the airAcid precipitation can damage life in lakes and

streamsEffects of acid precipitation on soil chemistry are

contributing to the decline of some forestssulfur dioxide (SO2) and nitrogen oxide (NOx)

gases and their ions—sulfates and nitrates react with the molecules of H2O to make acid rain