Chapter 8

Acids, Bases and pH

 

 

Acids:

-         foods taste sour-lemons, fruits and citric acid

-         dissolve in water- they ionize

-         Hydronium ions- H₃O⁺ -form when acids dissolved in water

-         When dissolved in water- all acids will conduct electricity

-         Indicators-concentration of hydronium ions in water by changing color-blue litmus paper

-         Blue litmus turns red with acids

-         Ionization process- electrolyte-substance that conducts electricity when dissolved in water-example-nitric acid-strong acid-ionzes completely when dissolved in water-strong electrolytes

-         Weak acids-acetic acid-do not conduct electricity

-         Table 1 page 258

Bases:

-         soapy taste-solutions feel slippery

-         table 2 page 259

-         strong bases-hydroxide ions-also known as metal hydroxides-dissociate-completely separates in water

-         Hydroxide ions- OH^- - Bases that dissolve in water release OH

pH:

-         indicator-litmus paper

-         Measure concentration hydronium (H₃O⁺) ions

-         Neutral Solutions- concentration of H₃O⁺ = OH^- ions

-         Figure 6 page 261

-         Concentration as a molarity (M) or number of moles of the substance per liter of solution

-         Hydronium Ion (H₃O⁺) = 10^-7 = negative power of 10

-         Example: apple juice = 10^-3 = pH 3

Reactions of Acids and Bases:

-Neutralization Reaction-

          HCl and Magnesium Hydroxide (antacid)

-spectator ions- watching on sidelines- do not change during chemical reaction

- when acid reacts with base-water formed from hydronium & hydroxide and salt formed

-Neutralization depends on amounts of acids and bases                                

-Titration-adding one solution to another solution in the presence of an indicator (changes color when acid and base in solution equal concentration) Bromthymol Blue

-Equivalence point- can be reached at pH’s other than 7 (neutral)- strong base with weak acid, strong acid with a strong base and strong acid with a weak base

-Salts-formed from neutralization and other salts, examples-baking soda, sodium hydrogen carbonate, calcium carbonate etc..

- Examples: Milk curdles when lemon juice

Household Uses & Items:

-         soap is an ionic compound- (carboxylate group – COO^-)- dissolve in water-emulsifier surrounding droplets of oil. Do not work in hard water- water that contains ions Mg²⁺, Ca²⁺ and Fe³⁺

-         Detergents-sodium potassium, and sometimes ammonium salts- made from petroleum

-         Ammonia-ammonia gas in water

-         Disinfectant-kills bacteria and viruses-bleach-sodium hypochlorite- NaOCl- acid added to bleach-chlorine gas released- example vinegar & bleach

-         Dyes-salts

-         Antacid-bases-magnesium hydroxide (milk of magnesia)

-         Vitamin C- asorbic acid

-         Shampoo- detergents- pH balance between 5 & 8

-         Buffer Aspirin- minimizes the effect of acid in an aspirin on the stomach

-         Bleaches-color safe-non-chlorine-oxidizing agents

-         Toilet Bowl Cleaners- hydrocholoric acid

-         Lye- strong base sodium hydroxide