Acids And Bases Lecture Notes

Acids , Bases , and pH Chapter 2

Concentration # of grams of solute # of Liters of solution  Units is grams per Liter g/L  The bigger the #, the more concentrated, the smaller the #, the more dilute  

Ruben 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 bases A 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 

Water



H+

+ OH-

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 scale

 The 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

water  Acid

 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

Buffers pH of most cells in body is kept between 6.5

and 7.5 Enzymes 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 E

Controlling 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 base Vinegar (acetic acid) is a weak acid Heartburn…what do you do? 

Acid Precipitation Acid precipitation refers to rain, snow, or fog with

a pH lower than 5.6 Acid precipitation is caused mainly by the mixing of different pollutants with water in the air Acid precipitation can damage life in lakes and streams Effects of acid precipitation on soil chemistry are contributing to the decline of some forests

sulfur dioxide (SO2) and nitrogen oxide (NOx)

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