acids and bases. what is an acid? an acid is a solution that has an excess of h+ ions. it comes from...
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Acids and Bases
What is an acid?An acid is a solution that has an
excess of H+ ions. It comes from the Latin word acidus that means "sharp" or "sour".
The more H + ions, the more acidic the solution.
AcidsSubstances that donate hydrogen ions (H+) to
water to form H3O+ Called the hydronium ionHCl hydrochloric acid used in poolsH2SO4 sulfuric acid- battery acid
HC2H3O2 acetic acid- vinegar
HC6H7O7 citric acid- lemons, limes
Properties of an Acid
Tastes Sour Conduct Electricity Corrosive, which means
they break down certain substances. Many acids can corrode fabric, skin, and paper
Some acids react strongly with metals and form H+
Turns blue litmus paper red
Picture from BBC Revision Bites http://www.bbc.co.uk/schools/ks3bitesize/science/chemistry/acids_bases_1.shtml
AcidsThe ones in food are diluteConcentrated acids are dangerousThey can burn you skin and eyesStrong acids ionize completely
All the H’s make hydroniumHCl + H2O Cl- + H3O+
Makes lots of ionsAre dangerous
AcidsWeak acids only partially ionize
Only a few H’s attach to waterHC2H3O2+ H2O C2H3O2
- + H3O+
Can be dangerous if concentrated
Uses of Acids (list 3 Examples)Acetic Acid = VinegarCitric Acid = lemons,
limes, & oranges. It is in many sour candies such as lemonhead & sour patch.
Ascorbic acid = Vitamin C which your body needs to function.
Sulfuric acid is used in the production of fertilizers, steel, paints, and plastics.
Car batteries
What is a base?
A base is a solution that has an excess of OH- ions.
Another word for base is alkali.
Bases are substances that can accept hydrogen ions
BasesIncreases the amount of OH- in solutionEither has OH- in itOr takes an H off of waterKOH - in drain cleanerNaOH - in drain cleanerNH3- ammonia
Properties of a Base
Feel SlipperyTaste BitterCorrosiveCan conduct electricity.
(Think alkaline batteries.)Do not react with metals.Turns red litmus paper
blue.
BasesKOH K+ + OH-
Strong bases ionize completelyMake lots of ionsAre dangerous NH3 + H2O NH4
+ + OH-
Weak bases only make a few ionsAre dangerous if concentrated
Uses of Bases (List 3 Examples)Bases give soaps, ammonia,
and many other cleaning products some of their useful properties.
The OH- ions interact strongly with certain substances, such as dirt and grease.
Chalk and oven cleaner are examples of familiar products that contain bases.
Your blood is a basic solution.
pH ScalepH is a measure of how acidic or
basic a solution is.• The pH scale ranges from 0 to 14.
Acidic solutions have pH values below 7
A solution with a pH of 0 is very acidic.
A solution with a pH of 7 is neutral.• Pure water has a pH of 7.
• Basic solutions have pH values above 7.
pH Scale
• A change of 1 pH unit represents a tenfold change in the acidity of the solution.
• For example, if one solution has a pH of 1 and a second solution has a pH of 2, the first solution is not twice as acidic as the second—it is ten times more acidic.
Acid – Base Reactions
A reaction between an acid and a base is called neutralization. An acid-base mixture is not as acidic or basic as the individual starting solutions.
Neutralization ReactionsAcids and bases react and neutralize each
otherStrong acids make lots of ionsHCl + H2O H3O+ + Cl-
Strong bases make lots of ionsNaOH Na+ + OH-
andH3O+ + OH- 2H2O
Neutralization ReactionsPut acids and bases togetherH3O+ + Cl- + Na+ + OH- Cl- +Na+ +2H2OThe Na+ and Cl- make salt which is neutralWater is neutralAll ionic compounds are saltsWill be neutral if the right amounts of strong
acids and bases are added
Neutralization ReactionsWeak bases will neutralize a strong acid,
but not as well.You need to add more of themIf you add enough, it will make the
solution basicSame works for weak acids and strong
basesAs you add acid to a base the pH dropsAs you add base to and acid the pH rises
Acid – Base reactions
Each salt listed in this table can be formed by the reaction between an acid and a base.
SoapWater and oil don’t mixWater is polarOil is nonpolarSoap can dissolve in both oil and waterMade by mixing fats with lye (NaOH)
SoapC O-
CH3
CH2 CH2
CH2CH2
CH2
CH2
CH2
O-
O-
Soap
Hydrophobic non-polar end
C O-
CH3
CH2 CH2
CH2CH2
CH2
CH2
CH2
O-
O-
Soap
Hydrophilic polar end
C O-
CH3
CH2 CH2
CH2CH2
CH2
CH2
CH2
O-
O-
C O-
CH3
CH2 CH2
CH2CH2
CH2
CH2
CH2
O-
O-
_
A drop of grease in water
Grease is non-polarWater is polarSoap lets you dissolve
the non-polar in the polar.
Hydrophobic ends dissolve in
grease
Hydrophilic ends dissolve in
water
Water molecules can surround and dissolve grease.
Helps get grease out of your way.
DetergentsSoaps react with minerals in hard water and
form scum that doesn’t dissolveDetergents have the same basic structure but
have a sulfur at the end,And start from petroleumDissolve in hard water
AmmoniaNH3 dissolved in water makes a weak base
NH3 + H2O NH4+ + OH-
The OH- ion reacts with grease and makes an emulsion which can wash away
Slippery
Household Uses (List 3 Examples)Antacids- Weak bases that neutralize excess
stomach acidShampoo- made from detergentsNeed to keep pH between 5 and 8 or it will
make the hair dullCitric acid keeps fruit from browningAcidic marinades tenderize meatsDrain cleaners are strong bases
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