Acids

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Acids Bases
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Goals

• To determine the difference between Acids Bases
• Discuss the importance of studying Acids Bases

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When an IONIC compound is placed in water, it
will break apart into two ions. If one of those
ions is H... The solution is acidic. If one of
the ions is OH-... The solution is basic.
HCl(g)
NaOH(s)
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Acidic solution
Alkaline solution
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Formulas - Acids

• In general, acids are identified by the hydrogen
  in the front of its chemical formula. For
  example, the formula for hydrochloric acid is HCl
  
• Others are Sulfuric acid H2SO4 Carbonic acid
  H2CO3 and nitric acid HNO3.
• Some exceptions to this rule are some organic
  acidssuch as acetic acid (CH3COOH)have their
  formulae designated according to their structure.

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Formulas - Bases

• Bases can often be identified by the OH term in
  the end of their chemical formula, as seen in
  sodium hydroxide NaOH, magnesium hydroxide
  Mg(OH)2 and potassium hydroxide KOH.
• There are some exceptions to this rule ammonia
  gas NH3
• Some organic acids have formulae that make them
  look like bases. Acetic acid (CH3COOH) for
  example.

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The Arrhenius theory

• Acids dissolve in water to produce hydrogen ions,
  H (more corrrectly, the hydronium ion H3O)
• Bases produce the hydroxide , OH- ions.
• This theory, while essentially correct, has been
  superseded by the Brønsted-Lowry theory

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Characteristics - differences

• Acids
• Tastes sour
• Turns litmus paper red
• React with some metals to give off H2 gas.
• React with carbonates to produce CO2 gas
• pH of 0 7
• Have an excess of H ions in solution.

• Bases
• Tastes bitter
• Turns litmus paper blue
• Feels slippery to the touch
• pH of 7 to 14
• Have an excess of OH- ions in solution.

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Characteristics - similarities

• Both conduct electricity
• Acids and bases react together to form salts and
  water only. The process is called neutralization
• NaOH HCl H2O NaCl
• Both acids and alkalis cause colour changes in
  certain substances called indicators, such as
  litmus

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Identifying Acids and Bases

• Acids have a ph from 0-7
• Lower pH value indicates a stronger acid.
• Bases have a pH from 7-14
• Higher pH value indicates a stronger base.

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Definitions of Acids and Bases

• An acid is a substance that breaks into
  ions in an aqueous solution.
• A Base (alkaline) is a substance that breaks into
  ions in an aqueous solution.
• Note aqueous solution is any solution where
  is the solvent.

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Characteristics Of Acids

• Acids can be characterized by
• A sour taste.
• It turns blue litmus paper red
• It tastes sour. Try drinking lemon juice (citric
  acid)

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Characteristics of Bases

• A Base is characterized by
• A bitter taste. (Milk of Magnesia)
• It feels slippery. (Soapy Water)
• It turns Red Litmus Blue.

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Mini-quiz to check your understanding1. What
element is in most acids and bases?

• Water
• Hydrogen
• Sulfur

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2. Which pH indicates the material is acidic?

• 5.0
• 7.0
• 9.0

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3. Why should you be careful dealing
with acids?

• They can eat your skin away
• They can cause an upset stomach
• They smell real bad

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5. Which is a base?

• CH3COOH
• NaOH
• NaCl

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6. What can a gardener do if the soil is too
acidic?

• Add a base such as lime or chalk to reduce
  acidity
• Add lemon juice to reduce the acidity
• Add salt (NaCl) until the soil becomes a base

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What is the pH scale?

• The pH scale measures how acidic or basic a
  solution is.

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The pH scale

• The pH scale is the concentration of hydrogen
  ions in a given substance.
• the power of Hydrogen

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Did we Miss something??

• What happens when the pH of a substance is 7?
• Ans A pH level of 7 indicates a Neutral
  Substance i.e Water!

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Test Your Knowledge

• What is the range of an ACID on the pH scale?
• Ans 0-7
• What is the range of a BASE and what is another
  name for a BASE?
• Ans 7-14, Alkaline

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Why Learn about Acids Bases?

• What do you think is the pH level of Toronto tap
  water?
• The pH of a swimming pool must be checked
  periodically. Why?
• Is it important for Lakes Rivers to maintain a
  certain pH?

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Naming Acids

• Binary acids
• HF hydrofluoric acid
• HBr Hydrobromic acid
• HI
• HCl

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• Acids with polyatomic ions
• H2SO4 Sulphuric acid
• HNO3 Nitric Acid
• H2CO3 Carbonic Acid

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Acid-Base Indicators

• Certain chemicals have the special property of
  appearing in different colours depending on the
  pH of the solution they are in.
• Such chemicals are known as acid-base indicators
• A couple of drops of indicator in a solution
  will indicate its pH.

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Three commonly used indicators.
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Neutralization Reactions

• What would happen if an acid and a base were
  mixed up?
• What would happen if a hydrogen ion (H) from an
  acid reacted with a hydroxide ion (OH-) from a
  base? 

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Neutralization - reaction of an acid and base
forming a salt and water.

HCl    NaOH 
  NaCl    HOH
Salts - composed of the positive half of a base
and the negative half of an acid.
Question
  What acid and base react to produce each of
these salts? CaSO4       NH4NO3       CaCl2