Transcript Properties of Acids & Bases

PROPERTIES OF ACIDS &
BASES
WEEK OUTLINE:

Monday: Properties of Acids & Bases

Tuesday: Acid Precipitation

Wednesday: Properties of Acids & Bases Lab
Stations

Thursday: Neutralization Reactions

Friday: Acid/Base Quiz

Making an Indicator – Acids & Bases at Home Lab
NEXT WEEK:

Monday (Dec 14): Review Class

Tuesday (Dec 15): Chemistry Test

Wednesday- Friday (Dec 16-18) Start Climate
Change Unit
WHAT DO YOU THINK?
Page 265: True or False?
 Stomach acid can dissolve metals like a coin in a
child’s stomach?
 We all contribute to the production of acid
precipitation?
 Even diet soda drinks can cause tooth decay?
 Medications for heartburn work by cooling the
stomach?
 All acids are dangerous?
 Soft drinks can be used to make spilled drain
cleaner safer?

PROPERTIES OF ACIDS AND BASES
Young children like to explore by putting things
in their mouths
 Occasionally objects get swallowed!
 Coins are the most common object to be
swallowed
 Once in the stomach, the coin in bathed in a
corrosive mixture that includes hydrochloric acid
(HCl (aq)) and other digestive juices
 The concentration of HCl in your stomach is
about the same as ones we have used in class what do you think happens to the coin?

PROPERTIES OF ACIDS
 Chemists
classify substances by their
properties
 Acids - are substances that react with metals
and carbonates, conduct electricity, turns
blue litmus red, and neutralize bases
 Acids also taste sour, but you should never
taste chemicals in a lab!
 Very useful in food industry - act as
preservatives (vinegar and lemon juice)
PROPERTIES OF ACIDS
 Reaction
with Metals
 Acids react with metals to produce
hydrogen gas
 Ex. hydrochloric acid + zinc → hydrogen
gas + zinc chloride
 2HCl (aq) + Zn (s) → H2 (g) + ZnCl2
(aq)
PROPERTIES OF ACIDS
 Reaction
with Carbonates
 Acids react with carbonates to produce
carbon dioxide gas
 Ex. acetic acid + sodium hydrogen
carbonate → carbon dioxide + water +
sodium acetate
HC2H3O2 (aq) + NaHCO3 (aq) → CO2
(g) + H2O (l) + NaC2H3O2 (aq)
PROPERTIES OF ACIDS
 Electrical
Conductivity
 Many acids are good conductors of
electricity
 A solution can only conduct electricity if it
contains ions
 Since acids are molecular compounds
they do not contain ions
PROPERTIES OF ACIDS
 Electrical
Conductivity (Continued)
 However, collisions with water molecules
break acid molecules apart to form cations
(hydrogen ions) and anions
 Ex. Hydrochloric acid forms hydrogen and
chloride ions:

HCl (aq) → H+ (aq) + Cl- (aq)
CHEMICAL FORMULAS OF ACIDS
All acids produce hydrogen ions when dissolved
in water
 Hydrogen ions give acids their properties
 The chemical formula of an acid begins with an H
and is usually followed by an “(aq)”
 This is because an acid shows its properties
when dissolved in water
 Hydrogen chloride - gas that would dissolve in
water in lungs when inhaled = forming highly
corrosive hydrochloric acid

NAMES OF ACIDS
 Two
common groups of acids:
 Binary Acids (Table 1 Page 269)
Acid Name
Chemical Formula
Hydrofluoric acid
HF (aq)
Hydrochloric acid
HCl (aq)
Hydrobromic acid
HBr (aq)
Hydrosulfuric acid
H2S (aq)
NAMES OF ACIDS

Oxyacids – related to polyatomic ions (Table 2
Page 269)
Acid
Chemical
Formula
Related
polyatomic ion
Polyatomic ion
name
Acetic acid
HC2H3O2 (aq)
C2H3O2- (aq)
Acetate
Nitric acid
HNO3 (aq)
NO3- (aq)
Nitrate
Carbonic acid
H2CO3 (aq)
CO3-2 (aq)
Carbonate
Sulfuric acid
H2SO4 (aq)
SO4 -2 (aq)
Sulfate
Phosphoric acid
H3PO4 (aq)
PO4 -3 (aq)
Phosphate
PROPERTIES OF BASES

Bases - conduct electricity, change the colour of
acid-base indicators, feel slippery and taste bitter
PROPERTIES OF BASES
Electrical Conductivity
 Bases are electrolytes, meaning their solutions
are good conductors of electricity
 Ex. NaOH (sodium hydroxide) is an electrolyte
because in water it separates into ions as it
dissolves


NaOH (s) → Na+ (aq) + OH- (aq)
Many common bases are ionic compounds - they
are made up of ions (unlike acids)
 As they dissolve in water, their ions are released

NAMES AND CHEMICAL FORMULAS
OF BASES

Table 4 Page 271
Base
Chemical Formula
Sodium hydroxide
NaOH (aq)
Calcium hydroxide
Ca(OH)2 (aq)
Ammonium hydroxide
NH4OH (aq)
Magnesium hydroxide
Mg(OH)2 (aq)
Aluminum hydroxide
Al(OH)3 (aq)
Sodium hydrogen carbonate
(baking soda)
NaHCO 3 (aq)
COLOUR WITH ACID-BASE
INDICATORS

A substance that changes colour depending on
the acidity or basicity of the solution is known as
an acid-base indicator
COLOURS OF COMMON SYNTHETIC
ACID-BASE INDICATORS

Table 3 Page 270
Indicator
Colour in Acid
Colour in Base
Bromothymol blue
Yellow
Blue
Phenolphthalein
Colourless
Pink
Pheol Red
Yellow
Red/pink
Litmus
Red
Blue
Methyl orange
Red
Orange/Red
THE PH SCALE
pH scale - a numerical scale of all the possible
values of pH from 0 to 14
 pH is a measure of how acidic or basic a solution
is
 A solution with a pH of 7 is considered neutral
 A solution with pH of less than 7 is considered
acidic
 A solution with pH of greater than 7 is
considered basic

THE PH SCALE CONTINUED
Solutions with highest hydrogen ion
concentration are near zero on pH scale
 Solutions with highest concentrations of
hydroxide ions are near 14 on pH scale
 Can use the words “acidity” or “basicity” to
describe the properties of acids or bases
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ACID AND BASE HOMEWORK
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Page 271 #1-5