Chapter 9

Acids & Bases

Acids•donate protons to water to form hydronium ions

•taste sour •turn cabbage juice red •turn litmus paper red•neutralize bases

Bases•donate hydroxide groups •accept protons •taste bitter •feel slimy •turn cabbage juice yellow, green or blue depending upon the solution concentration

•turn litmus paper blue

Everyday Uses for Acids

•digestion of food•clean metals•production of fertilizers•making explosives•carbonating beverages

What Makes a Compound an ACID?

When dissolved in water, all acids share certain physical & chemical properties

• sour taste• color change (litmus paper to red,

phenolphthalein turns colorless)• corrode metals• all contain hydrogen• produce a positive hydrogen ion when

dissolved in water (creates the hydronium ion H3O)

• known as proton donors

Three Common & Strong Acids

•HCl – hydrochloric acid

•H2SO4 – sulfuric acid

•HNO3 – nitric acid

•strong acids ionize to a high decree in water many H+ ions

•strong acids are good electrolytes

What is an Electrolyte?

•a substance whose water solution conducts an electric current

•Strong acids conduct electricity very well because they produce many ions in water

•Weak acids do not conduct electricity as well

Everyday Uses for Bases

•found in antacids (like Mylanta & Milk of Magnesia) to neutralize extra acids in the stomach

•used to make soaps (lye)•used to make household cleaner (ammonium)

•found in deodorants

What Makes a Compound a BASE?

When dissolved in water, all bases share certain physical & chemical properties

•bitter taste•color change (litmus paper to blue,

phenolphthalein turns bright pink)•slippery to the touch•all contain hydroxide ion OH-•known as proton acceptors

Three Common & Strong Bases

•KOH – potassium hydroxide•NaOH – sodium hydroxide

•Ca(OH)2 – calcium hydroxide

•strong bases readily dissolve in water to produce a high # of ions

•strong bases are good electrolytes (good conductors of electricity)

Acids & Bases in Solution

•Solutions can be acidic, basic, or neutral

•the pH scale is used to determine the acidity of a solution

•the pH of a solution is a measure of the hydronium ion (H3O+) concentration

Higher Concentration of H+

(proton donors)

Equal Concentra

tion of H+ and OH-

Higher Concentrationof OH-

(proton acceptor)

pH•the pH scale is a series of #s from 0 – 14

0 – 6 = acidic 7 = neutral (like distilled water)

8 - 14 = basic•strong acids have low pH numbers while strong bases have high pH numbers

pH of Comm

on Items

Formation of Salts• when acids react chemically with

bases, they for a class of compounds called the salts

• a salt forms from the positive ion of a base & the negative ion from an acid

• this reaction, called neutralization, also produces water as a by-product

• H+Cl- + Na+OH- → H2O + NaCl• What kind of reaction is

neutralization?

Precipitates•many of the salts created by the neutralization process do not dissolve in water

•they crystallize out of the solution to form a precipitate