Transcript Making Salts

Making Salts
Acid + excess
insoluble
solid
Acid + alkali
titration
Acid +
reactive metal
Acid + base
Acid +
carbonate
Direct combination
Precipitation
Soluble
salt
Insoluble
salt
Reactions of acids
Neutralisation of:
hydrochloric acid gives a chloride
sulphuric acid gives a sulphate
nitric acid gives a nitrate
Acid + metal  salt + hydrogen
Acid + base*  salt + water
Acid + carbonate  salt + water + carbon dioxide
*Base:
A metal oxide or metal hydroxide.
An alkali is a water-soluble base.
Salts
A salt is an ionic compound which is neither an acid
(containing H+) or a base (containing O2- or OH-). A salt is
formed whenever an acid is neutralised.
Acids, containing H+
Salts
Ionic compounds
Bases,
containing
OH- or O2-
Uses of Salts
• Plant fertilisers (NPK)
– (NH4)2SO4, NH4NO3, KH2PO4, …….
• Food flavour and preservation
– NaCl, KCl, KNO3…….
• In toothpaste
– NaF
• Photographic film
– AgCl, AgBr
Salts are important also in:
• Proteins and enzymes
– The molecules that carry out the chemical
reactions of life
• DNA and RNA
– the molecules of inheritance
• Transmission of electrical impulses along
nerves
Acid Neutralisation reactions
Neutralisation of:
hydrochloric acid gives a chloride (containing Cl-)
sulphuric acid gives a sulphate (containing SO42-)
nitric acid gives a nitrate (containing NO3-)
Acid + metal  salt + hydrogen
Acid + base  salt + water
Acid + carbonate  salt + water + carbon dioxide
Methods of salt making (1)
 salt
Acid
+
alkali
+
HCl (aq)
+
NaOH (aq)  NaCl (aq) +
Titration of acid against alkali for soluble salts of group 1 metals
and ammonium
5 cm3 sodium hydroxide solution was measured using a pipette
and transferred to the conical flask. 2 drops of methyl orange
indicator were added. Hydrochloric acid was poured into the
burette and the starting reading was recorded. The acid was
added to the sodium hydroxide, drop by drop, until the indicator
turned from yellow to orange (or red). Charcoal was added to
the mixture to absorb the indicator and was removed by filtration.
Water was evaporated from the filtrate, leaving sodium chloride
crystals.
water
H2O (l)
Methods of salt making (2)
• Acid + excess insoluble solid
– For all other soluble salts
– Solid is either a moderately reactive metal, a base or a
carbonate
– Excess solid to react with all the acid
• Removed by filtration
Methods of salt making (3)
• Precipitation reactions
– To make insoluble salts
– 2 solutions each containing one of the ions in
the salt are mixed.
– Salt is precipitated
– Salt is filtered, residue is washed on filter paper
and dried.
Methods of salt making (4)
• Direct combination of the elements
sodium (l) + chlorine (g)  sodium chloride (s)
2 Na (l) + Cl2 (g)
 2 NaCl (s)
aluminium (s) + bromine (l)  aluminium bromide (s)
2 Al (s)
+ 3 Br2 (l)  2 Al Br3 (s)
Methods of salt making (1)
(a)
barium hydroxide (aq) + nitric acid (aq)
Ba(OH)2 (aq)
+ 2 HNO3 (aq)
barium nitrate (aq) + water (l)
Ba(NO3)2 (aq)
+ 2 H2O (l)
Methods of salt making (1)
(b)
ammonium carbonate (aq) + sulphuric acid (aq)
(NH4)2CO3 (aq)
+
H2SO4 (aq)
ammonium sulphate (aq) + water (l) + carbon dioxide (g)
(NH4)2SO4 (aq)
+
H2O (l) + CO2 (g)
Methods of salt making (1)
(c)
ammonium hydroxide (aq) + nitric acid (aq)
NH4OH (aq)
+ HNO3 (aq)
ammonium nitrate (aq) + water (l)
NH4NO3 (aq)
+
H2O (l)
Methods of salt making (1)
(e)
potassium hydroxide (aq) + nitric acid (aq)
KOH (aq)
+
HNO3 (aq)
potassium nitrate (aq) +
KNO3 (aq)
+
water (l)
H2O (l)
Methods of salt making (2)
Acid
+
insoluble base
H2SO4 (aq) + CuO (s)

salt

CuSO4 (aq) + H2O (l)
+
water
Methods of salt making (2)
(g)
calcium (s)
Ca (s)
+
nitric acid (aq)
2 HNO3 (aq)
+
calcium chloride(aq) +
Ca(NO3)2 (aq)
hydrogen (g)
+
H2 (g)
Methods of salt making (2)
(f)
iron (s)
Fe (s)
+
sulphuric acid (aq)
+
H2SO4 (aq)
iron (II) sulphate (aq) +
FeSO4 (aq)
+
hydrogen (g)
H2 (g)
Methods of salt making (2)
(d)
calcium carbonate (s) + nitric acid (aq)
CaCO3 (s)
+ 2 HNO3 (aq)
calcium nitrate (aq) + water (l) + carbon dioxide (g)
Ca(NO3)2 (aq)
+
H2O (l) + CO2 (g)
Acid + metal  salt + hydrogen
Magnesium + hydrochloric acid  magnesium chloride + hydrogen
 MgCl2 (aq)
Mg (s)
+ 2 HCl (aq)
Mg (s)
+ 2 H+ 2 Cl- (aq)  Mg2+ 2 Cl- (aq)
2 ecopper + hydrochloric acid  no reaction
Cu (s)
Cu (s)
+ 2 HCl (aq)
+ 2 H+ 2 Cl- (aq)
+ H2 (g)
+ H2 (g)
React with cold water
React with dilute acids and steam
Potassium
Sodium
Lithium
Calcium
Magnesium
Zinc
Iron
Lead
Hydrogen
Copper
Silver
Gold
Platinum
Do not react with
dilute acids and steam
Reactivity
Metal Reactivity Series
Acid + base  salt + water
Sulphuric acid
+ copper oxide

copper sulphate + water
H2SO4 (aq)
+ CuO (s)

CuSO4 (aq)
2 H+ SO42- (aq)
+ Cu2+ O2- (s)

Cu2+ SO42- (aq) + H2O (l)
+ H2O (l)
Sulphuric acid + copper hydroxide  copper sulphate + water
H2SO4 (aq)
+ Cu(OH)2 (s)
2 H+ SO42- (aq)
+ Cu2+ 2 OH- (s)
 CuSO4 (aq) + 2 H2O (l)

Cu2+ SO42- (aq) + 2 H2O (l)
Carbonic acid
• H2CO3 (aq)
• 2 H+ CO32- (aq)
• Present in fizzy drinks:
H2CO3 (aq)  CO2 (g) + H2O (l)
Acid +carbonate  salt + water + carbon dioxide
Sulphuric acid + nickel carbonate  nickel sulphate + water + carbon dioxide
H2SO4 (aq) + NiCO3 (s)
 NiSO4 (aq) + H2O (l) + CO2 (g)
2 H+ SO42- (aq) + Ni2+ CO32- (s)  Ni2+ SO42- (aq) + H2O
CO(l)
+ CO2 (g)
3 (aq)