Chapter 6.3

•Acids, Bases, and pH

What are acids?

• substances that give up (donate) hydrogen ions when you dissolve them in water.

• the donated hydrogen ions H+ become bonded to water molecules, turning into

• H3O+ ions, called hydronium ions.

Characteristics of Acids

• sour taste• caustic (burns skin)• turns litmus paper pink (red)• solutions conduct electricity• everyday examples: • citrus fruits (oranges, lemons,

limes)• vinegar

common acids (page 201)

•HCl - hydrochloric acid

•H2SO4 - sulfuric acid

•HNO3 - nitric acid

What are bases?

• slippery (great for making soap!)• bitter taste• turns litmus paper blue• solutions conduct electricity• produce -OH (hydroxide) ions when

dissolved in water

Common bases (page 202)

• KOH - potassium hydroxide• NaOH - sodium hydroxide-• (common name=lye)

• Ca(OH)2 - calcium hydroxide

• NH3 - ammonia

Indicators

• substances you add to see if something (another substance) is an acid or a base.

• pink (usually called red, but it really isn’t)• turns blue when substance is a base• blue litmus turns pink (“red”) when acid• pH paper turns various colors, which

indicate strength of acid or base

Other indicators

• Red Cabbage Juice - stinks, but makes really great colors that tell us whether substances are acids or bases.

Indicator

• If you miss the indicator lab planned for section 6.3, be sure you get the results from another student, or Mrs. Peterson.

pH

• scale 0-14• 7 is neutral - not an acid, not a base• distilled water is neutral• below 7 is acidic• lower the number, the stronger the acid• above 7 is basic• higher the number, the stronger the

base

Neutralization reaction

• What do you do when you have some strong acid and don’t want it anymore? Pour it down the drain? Bad idea.

• Equally bad idea would be pouring a strong base down the drain. Both acids and bases can really do damage to materials.

Neutralization to the rescue!• But if you add an acid and a base

together, look what happens -

•HCl + NaOH ----> NaCl + H2O

Neutralization

• Now instead of two substances that could harm your plumbing pipes, HCl (hydrochloric acid) and NaOH, sodium hydroxide), you’ve combined them and they form harmless NaCl, a salt, and water.

Salt

• Note: NaCl is what we call salt in everyday life. But it’s just an example of what chemists call “salt”- in chemistry

• A SALT IS A COMPOUND FORMED WHEN YOU COMBINE AN ACID AND A BASE.

Salt

• Text definition: an ionic compound composed of cations bonded to anions.

• The anion comes from the acid (HCl gives up Cl-)

• The cation comes from the base (NaOH gives up Na+ )

• Now the H from the acid and the OH from the base get together to form H-OH, or H2O

Neutralization

• You will not completely neutralize an acid and a base unless you have just the right amounts and just the right strengths.

• This makes sense. If you had a large amount of some really strong acid, obviously throwing a few Tums (antacid) into the acid isn’t going to help much!

Home safety

• DO NOT mix home cleaning products unless you know exactly what is in them.

• Mixing:• Ammonia and bleach• or• Vinegar and bleach• produce dangerous substances!