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Chemical Changes (Salts from Metals (Acids, metals, salts Metal + acid…
Chemical Changes
Salts from Metals
Acids, metals, salts
Metal + acid reaction = metal above H
All acids contain Hydrogen
Acid dissolved in water - H released
A Salt
A compound formed when the hydrogen in an acid is wholly, or partially, replaced by metal (or ammonium) ions
Equations
Acid +
Base/Alkali
= Salt +
Water
Acid +
Carbonate
= Salt +
Water
+
Carbon
dioxide
Acid +
Metal
= Salt +
Hydrogen
Acid + Ammonia Solution = Ammonium salt + Water
Metal affects type of salt
Metal + Acid
Always a
redox
reaction
Alkali metals too dangerous for acid
Water lost in
crystallisation
Saturated - pure, dry crystals appear (edges)
Dipping
glass rod in hot salt solution
Crystals
form in solution left
on rod
Salts
Hydrochloric - chloride; Sulphuric - sulphate
Nitric - nitrate; Phosphoric - phosphate
Metal + acid explained
Mg(s) + H2SO4(aq) = MgSO4(aq) + H2(g)
Mg(s) + 2H
+
(aq) = Mg
2+
(aq) + H2(g)
Mg(s) = Mg
2+
(aq) + 2e
-
2H
+
(aq) + 2e
-
= H2(g)
Sulphate ions don't change
They're
spectator ions
Displacement reactions
In aq solutions
More reactive displace less reactive metals
Non-metals in Rseries
- Hydrogen, Carbon
Oxidation
= loss of electrons
Reduction
= is the gain of electrons
:star:
Displacement
:star:
A more reactive metal will displace
a less reactive metal from an aqueous solution
of one of its salts
Ionic equation:
Only
atoms, ions
that change in equation
Balanced
Mg(s) + CuSO4(aq) = MgSO4(aq) + Cu(s)
Ionic
Mg(s) + Cu(2+)(aq) = Mg(2+)(aq) + Cu(s)
Hydrogen and Carbon
Metal + acid = H displace
(Cu can't, Pb can)
Metal extraction = C displace
(Displace metals from oxides)
Below AI
Oxidation
-
Loss of electrons
Reduction
-
Gain of electrons
Iron + Copper Sulphate
Fe(s) + Cu(2+)(aq) = Fe(2+)(aq) + Cu(s)
Half equation
Fe(s)= Fe(2+)(aq) + 2e-
Cu(2+)(aq) + 2e- = Cu(s)
Displace react = redox reactions
(reduction-oxidation)
Extracting metals
Metals
Bikes, Cars, Trains, Planes
Found in
Earth's crust
Most combined chemically
W/ elements like O or S
Must be
separated before use
Extraction depends on reactivity
Ores
Mined from ground
Some then concentrated
Before extraction, purification
Copper ores concentration
Ground
to powder
Mix
- powder, water, chemical
(makes Cu repel water)
Air bubbled through
, Cu
floats
(froth)
Conc. Cu compound
scraped off
top
Very unreactive metals in native state
Gold nuggets:
Big - pick able; Small - planning (separation)
Viability:
Ease of Extract
(Cheap methods, Efficiency)
Amount in ore
Demand for metal
(economic source/ low grade)
Carbon reduction
Many metals come as oxides
Below C - Heat with carbon
metal + carbon = metal + carbon dioxide
Hydrogen Reduction
Tungsten makes carbide
So H used (makes water)
(
Above C: Electrolysis
- molten)
Strong and weak acids
Dilute/Concentrated
Amount of solute in given volume
6.0
mol/dm3 -
corrosive
0.1
mol/dm3 -
irritant
Strong acids:
Hydrochloric
acid
Nitric
acid
Sulphuric
acid
Weak/Carboxylic acids:
Ethanoic
acid (vinegar)
Citric
acid (citrus fruit)
Carbonic
acid (rainwater, fizzy drinks)
Acid strength
Stronger
-
faster
reaction w/ carbonate
Stronger
-
More acidity
per mol/dm3
Acids ionise in water
; show their properties
Stronger
-
More
molecules are
ionised
Weaker
- Less ionised, reaction is
reversible
Concentration of H ions
Strong acids ionise completely
Concentration of
H same as molecules
1
pH
unit = H
+
Conc. by
factor of 10
0.1 m/d = 1 pH
0.01 m/d = 2 pH
0.001 m/d = 3 pH etc
The reactivity series
:star:
Rseries
:star:
List of metals in order of their reactivity,
with most reactive metals at the top
and the least reactive ones at the bottom
Ores:
Rocks from which it is
economical to extract
the metals they contain
Metals in ores
oxidised
metal
reduced
in extraction
Metal + Water
Great range of reactivity
Most don't react vigorously
Copper
doesn't react (water pipes)
1) Potassium 2) Sodium 3) Lithium
Mg - days
to react legible amount of H
Fizz
- K, Na, Li, Ca;
Slow
- Mg, Al, Zn, Fe
Slight
(steam) - Sn, Pb;
None
- Cu, Ag, Au
Metal + acid
If
water
reactions are
slow
Used instead
to find order
Explosive - K, Na, Li,
Fizz - Ca, Mg, Al, Zn, Fe
Slow (warm acid) - Sn, Pb
None - Cu, Ag, Au,
Salts from insoluble bases
Bases
Compounds that
neutralise
acids
Alkali = soluble
bases
E.g. Alkali metal
Hydroxide
Bases mostly
metal oxides
E.g. Trans metal oxides
Salts
(+)metal ions and (-)ions from acid
Ionic compound, no overall charge
Can also involve (+)ammonium ions
Copper Salt
Copper(II) oxide + Sulphuric acid
Oxide
is an
insoluble
base
Makes
Copper sulphate
crystals
H2SO4 + CuO = CuSO4 + H2O
Mix
and warm reactants
Turns
blue
in reaction, excess oxide
Filter
solution to remove excess
Evaporate water -
crystallisation
Neutralisation
& the pH scale
Acidity
Soluble
hydroxides =
alkali
(sodium hydroxide)
Acid
neutralisers
=
bases
(metal oxides/hydroxides)
Water =
neutral
-
not
acidic/alkaline
Acid
has a
sour
taste
(Citric acid, Ethanoic acid etc)
Hydrochloric acid
Gas
hydrogen chloride
dissolved in water
Excess H
+
(aq) ions = acidity
All acids release
H+ ions
into aq solution
Sodium Hydroxide Solution
Solid sodium hydroxide dissolved in water
All alkali form
OH- ions
in aq solution
Excess OH
-
(aq) ions = alkalinity
Measurement
Indicators -
change colour
with acidity
Litmus =
red
in acid,
blue
in alkali
Measure in
pH scale
(acidic)0 - 14(alkaline)
Universal Indicator
Special, a few dyes - colours of pH scale
pH 7 = neutral
pH meter and sensors
Glass probe
w/ dip in test solution
sensors -
digital display
/
data loggers
(comp.)
record and monitor
pH change over time
Making more salts
Acid + Alkali
E.g. HCl + NaOH
Neutralisation
:
H+
ions react w/
OH-
ions
Ions react to form water
H
+
(aq) + OH
-
(aq) = H2O(l)
Ammonia + Water
NH3(aq) + H2O(l) = NH4
+
(aq) + OH
-
(aq)
Pure sample
Titration
w/ indicator, find acid amount for
neutralisation
Run volume w/o indicator;
Crystallise
the solution
Acid + Carbonate
Limestone
= mostly calcium carbonate
Suffers damage from
acid rain
Makes salt, water,
carbon dioxide
Most carbonates
insoluble
(except Group 1)