Section A2.4
Unit A
Science 10

 At the end of this lesson, will be able to:
 Identify and classify acids and bases based on their properties
 Name acids and bases

 Important
 Control digestion in our bodies (stomach acid and activation and deactivation of enzymes)
 Found in foods and used in industry

 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

 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)
 Neutral: paper stays same color
ACI D
RE D
B ASE
B LUE

 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?

 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 nonmetals)
 To identify acids from formulas, look for “H” on the left or “-COOH” on the right

 Which of the following are acids?
HBr(aq) NaCl(aq) H2SO4(aq) HCOOH(l)
NaOH(aq) H2O(l) HNO3(aq) C
6
H
5
COOH(l)
K2SO4(aq)

 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?

 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 (SO4 2) and is then named sulfuric acid
 What is the acid name of H3PO4
(aq) approach naming it?
? How do we

 3) if anion ends in “ite”, name of acid ends in “ous”
 H
2
SO
3 (aq) contains the anion sulfite (SO named sulfurous acid
3
2), so the acid is
 What is the name of the acid HNO
2(aq)
?

Acid Formula
HNO3
(aq)
H2CrO4
(aq)
HI
(aq)
HBr
(aq)
HClO
(aq)
Name nitric acid chromic acid hydroiodic acid hydrobromic acid hypochlorous acid

Back of periodic table sheet

 Often, bases are identified by presence of “OH ”
(hydroxide ion) with a metal ion or the ammonium ion (NH
4
+ )
 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 know?

Base
KOH(s)
NH4OH(aq)
Ca(OH)2
Mg(OH)2(s)
Al(OH)3(s)
Name 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

 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