Acids and Bases

Section A2.4
Unit A
Science 10
Objective Checklist
 At the end of this lesson, will be able to:
 Identify and classify acids and bases based on their
 Name acids and bases
Acids and Bases
 Important
 Control digestion in our bodies (stomach acid and
activation and deactivation of enzymes)
 Found in foods and used in industry
Acid or a Base?
 Taste:
 Acids- sour (ex. Lemons- citric acid)
 Bases- bitter (ex. Soap)
 Touch:
 Bases- slippery to the touch and corrosive to the skin
What does corrosive mean?
 Acids- not slippery and corrosive to the skin
 Reaction with Metal:
 Acids- react; forms H2 gas (bubble formation)
 Bases- don’t react
Using pH
 What is pH used for?
 What does the scale look like?
 What substance is considered neutral?
 Where do the following substances place on the scale?
 Acid rain, normal rain, lemon juice, stomach juices
 Baking soda, human blood, oven cleaner, window
cleaner (ammonia)
 Both acids and bases have or form ions in solution
 In solution, these ions can conduct electricity, so they
are electrolytes
 Can you think of any everyday items that contain an
acid or a base (alkali) to conduct electricity?
 To determine pH and whether something is an acid or
base, we use indicators
Indicators change color depending on pH
Litmus paper is created through extracting the
chemical from lichens
Acid: blue litmus paper turns red (BRA)
Base: red litmus paper turns blue (RBB) ACID
Neutral: paper stays same color
 What color should the acid (lemon juice, citric acid)
turn the blue litmus paper? Red litmus paper?
 What color should the base (bleach) turn the red
litmus paper? Blue litmus paper?
 How do we test whether the unknown is an acid or
base? If blue litmus stays blue, can we conclude that it
is a base? Why or why not?
Recognizing Acids
 In acids, the formula often has a “H” (hydrogen ion –
may be more than one) on the left side of the formula
(ex. HCl)
 Can also appear on the right side as “-COOH” (organic
acid group) (ex. CH3COOH)
 They are bonded to an anion (one or more non-
 To identify acids from formulas, look for “H” on the
left or “-COOH” on the right
Recognizing Acids
 Which of the following are acids?
Naming Acids
 IUPAC method: name as an aqueous ionic compound
 What would HCl be using these rules?
 Another method:
 1) When containing hydrogen and non-metallic element
(anion name ends in –ide):
 Use prefix “hydro” and suffix “ic”
 Ex. HCl becomes hydrochloric acid
What would HF be using this rule?
Naming Acids cont…
 2) When acid contains oxygen (ex. H2SO4(aq)), name
based on the anion
What is the anion in H2SO4(aq)?
 If anion ends in “ate”, name of acid ends in “ic”
 Ex. H2SO4(aq) contains sulfate anion (SO42-) and is then
named sulfuric acid
 What is the acid name of H3PO4(aq)? How do we
approach naming it?
Naming Acids cont…
 3) if anion ends in “ite”, name of acid ends in “ous”
 H2SO3 (aq)contains the anion sulfite (SO32-), so the acid is
named sulfurous acid
 What is the name of the acid HNO2(aq)?
Acid Formula
nitric acid
chromic acid
hydroiodic acid
hydrobromic acid
hypochlorous acid
For your reference
Back of periodic table sheet
Recognizing Bases
 Often, bases are identified by presence of “OH-”
(hydroxide ion) with a metal ion or the ammonium
ion (NH4+)
 It is more complicated than this, but for now:
 Any compound with high solubility and an OH on right
is a base
 Name base as would name an ionic compound
 What would NaOH be named using rules we already
potassium hydroxide
ammonium hydroxide
calcium hydroxide
magnesium hydroxide
aluminium hydroxide
 Reaction between acid and a base which produces
water and a salt
 The acidic and basic properties disappear
 Why would this be important? Give an example
 Ex. A bee’s sting contains methanoic acid which
dissolves nerve endings in the skin (lots of pain!).
Sting creams containing ammonia limit the pain as the
ammonia neutralizes the acid
Neutralization Demo
 What pH is water?
 Is vinegar an acid or a base?
 What color do we observe initially?
 If I add alka-seltzer (a base) predict the color change
 What do we observe as I add the base?
 Explain why this occurred

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