11. Acids and Bases.ppt
-
Upload
andrew-tung -
Category
Documents
-
view
215 -
download
0
Transcript of 11. Acids and Bases.ppt
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 1/24
Properties of acids
have sour taste
are hazardous
change the colour of indicators
Turns blue litmus paper red
reacts with metals to produce hydrogen gas
reacts with carbonates and hydrogen
carbonates reacts with metal oxides and hydroxides
Storage of acids and acidic foods should be in
glass, plastic or clay pots – Why?
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 2/24
Acids and Bases
Reaction with carbonates to produce salt, carbon
dioxide and water.
FeCO3 + 2HCl FeCl2 + H2O + CO2
Reactions of ACIDS
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 3/24
Acids and Bases
Reaction with carbonates to produce salt, carbon dioxide and water. Reactions of ACIDS
Reaction with reactive metals to producesalt and hydrogen gas.
Mg + H2SO4 MgSO4 + H2
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 4/24
Acids and Bases
Reaction with carbonates to produce salt, carbon dioxide and water. Reactions of ACIDS
Reaction with reactive metals to produce salt and hydrogen gas.
•Reaction with base to produce saltand water
CuO + 2HNO3 Cu(NO3)2 + H2O
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 5/24
Acids and Bases
Reaction with carbonates to produce salt, carbon dioxide and water. Reactions of ACIDS
Reaction with metals to produce salt and hydrogen gas.
•Reaction with base to produce salt and water
Reaction of bases with ammonium saltto produce salt, ammonia gas and water.
Reactions of BASES
NaOH + NH4Cl NaCl + NH3 + H2O
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 6/24
Uses of acids
Sulfuric acid in the manufacture of fertilisers
Ammonium sulfate – fertiliser
Detergents, paints, dyes, artificial fibers and plastics
Dilute sulfuric acid is used in batteries – cars,
buses HCl and H2SO4 are used to remove rust
Food preservations – vinegar
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 7/24
Properties of bases
Bases are oxides or hydroxides of metals.
All alkalis are bases and not all bases are
alkalis.
Insoluble metal oxides are bases. CuO
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 8/24
Bases
Alkalis
Bases
Any difference?
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 9/24
Any Difference?
Bases are oxides or hydroxides of metals.
Alkalis are soluble bases – which produces hydroxide ions in water.
All alkalis are bases and not all bases are
alkalis.
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 10/24
Bases
Alkalis
Bases
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 11/24
Alkalis and bases
Metal oxides insoluble in water are bases.
Example – CuO, Fe2O3,PbO2
Metal oxides soluble in water are alkalis –
Na2O, K 2O
Aqueous ammonia?
NH3(aq) -?
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 12/24
What did you observe in the lab?
NH3.H2O ?
NH3 + H2O NH4+(aq) + OH- (aq) ?
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 13/24
NH3OH
-
NH3
NH3
NH3
NH3
NH3
NH3
NH3
NH3
NH3NH4+
A small fraction of ammonia molecules react with water to
form hydroxide ions. Most ammonia molecules remainunchanged that is why you can smell the pungent gas when abottle of aqueous ammonia is opened.
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 14/24
Hazardous
Soapy to touch Change colour with indicators
Reacts with acids
NaOH + HCl → NaCl + H2O Reacts with ammonium compounds
NH4Cl + NaOH → NaCl (aq)+ H2O(l) + NH3(g)
Reacts with metal ions
2NaOH(aq) +Cu2+ (aq)→ Cu(OH)2(s)+ 2Na+ (aq)
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 15/24
Strong and weak alkalis Sodium hydroxide and potassium hydroxide
completely dissociates (strong alkali)
NaOH(aq) → Na+ (aq) + OH- (aq)
weak alkali (aqueous ammonia)
NH3(g) + H2O(l) NH4+(aq) + OH- (aq)
A small fraction of ammonia molecules react
with water to form hydroxide ions.
Most ammonia molecules remain unchanged
that is why you can smell the pungent gas when
a bottle of aqueous ammonia is opened.
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 16/24
Strong alkalis and weak alkalis
Strong alkalis – dissociates completely in
water to produce a high concentration of
hydroxide ions. Example: NaOH, KOH
OH-
Na+
Na+
Na+Na
+
OH-
OH-
OH-
DILUTE CONCENTRATED
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 17/24
Weak alkalis
Weak alkalis – dissociates partially in water to
produce a low concentration of hydroxide ions.
NH3(aq) + H2O(l) NH4+(aq) + OH- (aq)
NH3OH
-
NH3
NH3
NH3
NH3
NH3
NH3
NH3
NH3
NH3
NH4+
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 18/24
Chemical reactions
Reacts with acids – Neutralisation reaction
NaOH (aq) + HCl (aq) → NaCl (aq) + H2O(l)
Reacts with ammonium compounds NH4Cl (aq) + NaOH (aq) → NaCl(aq) + H2O(l) +
NH3(g)
Reacts with metal ions
2NaOH(aq) +Cu2+ (aq)→ Cu(OH)2(s) + 2Na+ (aq)
2NaOH(aq) +Fe2+ (aq)→ Fe(OH)2(s) + 2Na+ (aq)
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 19/24
Strong alkalis react with amphoteric metal oxides
ZnO + 2NaOH + H2O → Na2(Zn(OH)4) SodiumZincate
Al2O3+ 2NaOH + 3H2O → 2NaAl(OH)4Tetrahydroxoaluminate
Electronegativity increases as you go across the period - and the electronegativity difference betweenaluminium and oxygen is smaller. That allows theformation of covalent bonds between the two.
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 20/24
Alkalis and indicators
Change colour with indicators
Methyl orange - yellow
Red litmus paper changes to blue
Phenolphthalein - peach
Universal indicator
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 21/24
OXIDES
METALLIC OXIDES NON-METALLIC OXIDES
BASIC OXIDES
Most
basic
oxides
are
_______ in
water.
Metal
oxides
that are
soluble in
water are
known as
__ _______.
AMPHOTERIC
OXIDES
ACIDIC
OXIDES
Acidic oxides
dissolve in
water to form
acids.
NEUTRAL
OXIDES
Metal oxides
that can react
with both
_________ and
_________ to
form salt and
water.ALKALIS
insoluble
NaOH
KOH
FeO
CuO
acids
alkalis
ZnO
Al 2O3
PbO
SO2
P2O5
NO2
H2O
NO
CO
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 22/24
OXIDES
METALLIC OXIDES NON-METALLIC OXIDES
BASIC OXIDES
Most
basic
oxides
are
Insoluble
in
water.
Metal
oxides
that are
soluble
in water
are
known
as
Alkalis.
AMPHOTERIC
OXIDES
ACIDIC
OXIDES
Acidic oxides
dissolve in water
to form acids.
NEUTRAL
OXIDES
Metal
oxides that
can react
with both
acids and
alkalis to
form salt
and water.
NaOH
KOH
Fe2O3
CuO
ZnO
Al2O3
PbO
SO2
P2O5
NO2
H2O
NO
CO
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 23/24
Li Be B C N O F
Na Mg Al Si P S Cl
K Ca Ga Ge As Se Br
Rb Sr In Sn Sb Te I
Cs Ba Tl Pb Bi Po At
Basic Oxides Amphoteric Oxides Acidic Oxides
I II III IV V VI VII
Acidic and amphoteric oxides
7/27/2019 11. Acids and Bases.ppt
http://slidepdf.com/reader/full/11-acids-and-basesppt 24/24
Uses of alkalis/bases
Window cleaners, oven cleaners, detergents,
soaps – sodium hydroxide. toothpastes – toneutralise the acids in our teeth, medicines for
indigestion - to neutralise stomach acid.
CaO is used to neutralise the acidity of the soil