National 4 & 5 Chemistry
Metal Chemistry, Electricity & Chemistry,
Examples Answers
NATIONAL 4 AND NATIONAL 5 CHEMISTRY
Unit 3: Chemistry in Society
METAL CHEMISTRY &
ELECTROCHEMISTRY
PRACTICE EXAMPLES BOOKLE
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Page 1 of 19
17-Mar-16
National 4 & 5 Chemistry
N4/5
Metal Chemistry, Electricity & Chemistry,
Examples Answers
N4/5
METAL REACTIVITY AND DATE OF DISCOVERY
Q1) Using the N5 Chemistry Data Booklet; complete the REACTIVITY SERIES OF METALS
with the Date of Discovery.
REACTIVITY SERIES OF METALS
METAL
DATE OF DISCOVERY
potassium (K)
1807
sodium (Na)
1807
lithium (Li)
1817
calcium (Ca)
1808
magnesium (Mg)
1808
aluminium (Al)
1825
zinc (Zn)
Ancient
iron (Fe)
Ancient
tin (Sn)
Ancient
lead (Pb)
Ancient
copper (Cu)
Ancient
mercury (Hg)
Ancient
silver (Ag)
Ancient
gold (Au)
Ancient
Q2) What conclusion can be drawn from the metals reactivity and the date it was discovered.
The more reactive the metal the later in history it was discovered, this would be due to
the level of technology and Chemistry knowledge needed for extraction.
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National 4 & 5 Chemistry
N4/5
Metal Chemistry, Electricity & Chemistry,
Examples Answers
METALS AND THEIR PROPERTIES
N4/5
1. Match the following terms to their definitions
electrical conductor
sonorous
flexible
lustrous
ductile
malleable
thermal conductor
lustrous
All metals are shiny when polished or
freshly cut
flexible
Metals do not break – they bend
ductile
Metals can be drawn into wires
malleable
Metals can be hammered into sheets
sonorous
Metals ring like a bell when hit - they
do not make a dull thud
Electrical conductor
All metals conduct electricity
Thermal conductor
Metals allow energy to flow through
them, causing heating
2. Which of the following are NOT properties of most metals?
strong
magnetic
brittle
hard
high melting point
3. Metal application is based on the properties that the metal or alloy will have. Identify the
properties of the metals which are important for the following uses.
1. Copper, iron, steel or aluminium are obviously
good conductors of heat and malleable. Copper is
one of the best conductors of heat but if you want a
pan made fully out of copper it would be expensive
for the consumer. Aluminium is also a metal that
conducts heat very well and isn't too expensive. Low
reactivity is important because acid is produced
when cooking. Stainless steel is a good metal
because it is tough, so withstands dishwashers and
damages. It is non-reactive which means certain
acidic foods won't be discoloured, which may be the
case with aluminium pans. A solution to this would be
a stainless steel outside and have a copper or
aluminum core. This way it still conducts heat well,
doesn't cost too much and because it only has an
aluminum core, the metal won’t change the food.
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2. Copper is so ductile because
the layers of positive copper ions
can slip over each other whilst still
being held together by the 'sea' of
de-localised electrons. Copper has
the best electrical conductivity of
any metal, except silver. A good
electrical conductivity is the same
as a small electrical resistance.
Page 3 of 19
3. In 1943, Richard James, a naval
mechanical engineer stationed at
the William Cramp and Sons shipyards in
Philadelphia, was developing springs that
could support and stabilize sensitive
instruments aboard ships in rough seas.
James accidentally knocked one of the
springs from a shelf, and watched as the
spring "stepped" in a series of arcs to a
stack of books, to a table top, and to the
floor, where it re-coiled itself and stood
upright. James' wife Betty later recalled,
"He came home and said, 'I think if I got
the right property of steel and the right
tension; I could make it walk.'" Flexible,
ductile and malleable.
17-Mar-16
National 4 & 5 Chemistry
4. Silver and gold are very soft
metals and can be moulded into
different shapes they are very pure
forms of metals so there are very
little impurities. They are not very
reactive in open atmosphere i.e
almost inert metals. They are of
course lustrous.
Metal Chemistry, Electricity & Chemistry,
Examples Answers
5. Bronze is used because it has
the best sound, tone, and
resonance as well as multiple
harmonics. The tone and vibrato
are gorgeous. Other metals can be
used but are inferior in sound. The
Liberty Bell is bronze. Sonorous. It
also has high corrosion resistance.
“All that is gold does not glitter,
materials are alloys for strength
and other desired properties.
Steel, an alloy of iron, has various
types depending on the alloying
elements. It is strong and can
withstand a considerable force
(high compression strength in
comparison to concrete which is
Not all those who wander are
brittle. That is why concrete is
lost….” J.R.R. Tolken
7. Pure tungsten has some
amazing properties including
the highest melting point (3422
ºC), lowest vapour pressure,
and greatest tensile strength out
of all the metals. Because of
these properties it is the most
commonly used material for
light bulb filaments. Flexible,
ductile, thermal and electrical
conductor.
6. Most of the engineering
reinforced with steel.)
8. Testing of different material
blades like High Carbon Steel,
Low Alloy Steel, Bi-metallic
blade, High speed Steel blades
for their hardness, Cutting time
performance, Wear Resistance,
Tensile Strength and
performance under buckling is
essential in the manufacture of
high quality tools like a cutting
saw.
9. Lead lasts an average of more than
three times longer than other roofing and
flashing products. Lead is resistant to
corrosion from the atmosphere, salt water,
most natural chemicals, and UV
degradation. Lead is recyclable and can be
re-used. Sheet lead can be tightly dressed
around junctions and penetrations and is
the only material that can protect these
areas from water penetration. Lead is able
to cope with wide ranging temperature
fluctuations, and its malleability ensures no
cracking. Sheet lead installation is not
impacted by damp or cold weather
conditions.
10. Partly because brass does
not corrode in seawater and
partly because brass is not
magnetic and so does not
interfere with the compass
needle. Malleable and
flexible.
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11. Strong strength to weight
ratio. While the same can be
said of exotic metals like
titanium, aluminum is much
cheaper. Low density
2.70g/cm3. Malleable. Flexible.
Page 4 of 19
12. Lead is a fairly cheap metal,
which is good for fishing
weights that can get lost. It is a
soft malleable metal and
resistant to corrosion. Lead has
a high density 11.3g/cm3. The
other metals are not as good as
lead but share some of the
characteristics above. The
reason lead is being replaced is
lead is toxic.
17-Mar-16
National 4 & 5 Chemistry
N4/5
Metal Chemistry, Electricity & Chemistry,
Examples Answers
REACTION OF METALS WITH OXYGEN
N4/5
Copy and complete the following word and formula equations.
(N5 students should balance the formula equations.)
1.
(a)
metal
+
oxygen
Metal oxide
(b)
aluminium
+
oxygen
Aluminium
oxide
4Al
4Al(s)
+
+
3O2
3O2(g)
magnesium
+
oxygen
2Mg
2 Mg(s)
+
+
O2
O2(g)
Lithium
+
oxygen
4Li
4Li(s)
+
+
O2
O2(g)
Copper
+
Oxygen
Copper(ii)
Oxide
Cu
2Cu(s)
+
+
O2
O2(g)
CuO
2Cu2+O2-(s)
(c)
(d)
(e)
2.
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2 Al2O3
2(Al3+)2(O2-)3(s)
Magnesium
oxide
2MgO
2Mg2+O2-(s)
Lithium oxide
2Li2O
2(Li+)2O2-(s)
Write balanced ionic equations for the above reactions with state
symbols.
Page 5 of 19
17-Mar-16
National 4 & 5 Chemistry
N4/5
Metal Chemistry, Electricity & Chemistry,
Examples Answers
REACTION OF METALS WITH WATER
N4/5
Copy and complete the following word and formula equations.
(N5 students should balance the formula equations.)
1.
(a)
metal
+
water
Metal
hydroxide
+ hydrogen
(b)
calcium
+
water
Calcium
hydroxide
+ hydrogen
Ca
Ca(s)
+
+
2H2O
2H2O(l)
Ca(OH)2
+ H2
Ca2+(OH-)2(aq)
+ H2(g)
sodium
+
water
Sodium
hydroxide
+ hydrogen
2Na
2Na(s)
+
+
2H2O
2H2O(l)
2NaOH
2Na+OH-(aq)
+ H2
+ H2(g)
lithium
+
water
Lithium
hydroxide
+ hydrogen
2Li
2Li(s)
+
+
2H2O
2H2O(l)
2LiOH
2Li+OH-(aq)
+ H2
+ H2(g)
potassium
+
water
Potassium
hydroxide
+ hydrogen
2K
+
2H2O
2KOH
+ H2
2K(s)
+
2H2O(l)
2K+OH-(aq)
(c)
(d)
(e)
2.
N4/5
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+ H2(g)
Write balanced ionic equations for the above reactions with state
symbols.
REACTION OF METALS WITH ACID
Page 6 of 19
N4/5
17-Mar-16
National 4 & 5 Chemistry
1.
Metal Chemistry, Electricity & Chemistry,
Examples Answers
Copy and complete the following word and formula equations.
(N5 students should balance the formula equations.)
(a)
metal
+
acid
(b)
lead
+
Hydrochloric
acid
Pb
+
2HCl
Pb(s)
magnesium
+
+
2H+Cl-(aq)
Nitric acid
Mg
Mg(s)
+
+
Calcium
+
Sulphuric
acid
Calcium
sulphate
+ hydrogen
Ca
Ca(s)
+
+
H2SO4
(H+)2SO42-(aq)
CaSO4
Ca2+SO42-(aq)
+
+
Zinc
+
Nitric acid
Zinc (ii)
nitrate
+ hydrogen
Zn
Zn(s)
+
+
2HNO3
2HNO3(aq)
Zn(NO3)2
Zn2+(NO3-)2(aq)
+
+
(c)
(d)
(e)
2.
N4/5
2HNO3
2H+NO3-(aq)
Salt
+
hydrogen
Lead(ii)
chloride
+ hydrogen
PbCl2
+
Pb2+(Cl-)2(aq)
Magnesium
nitrate
+
H2(g)
+ hydrogen
Mg(NO3)2
Mg2+(NO3-)2(aq)
+
+
H2
H2
H2(g)
H2
H2(g)
H2
H2(g)
Write balanced ionic equations for the above reactions with state symbols.
EXTRACTING METALS FROM ORES
N4/5
1. Describe briefly the three methods that are used to extract metals from their
ores.
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17-Mar-16
National 4 & 5 Chemistry
Metal Chemistry, Electricity & Chemistry,
Examples Answers
2. Which metals occur naturally? Gold and silver.
3. Which metals are extracted using carbon? Zinc, iron, nickel, tin, lead and
copper
4. Which metals have to be extracted by electrolysis of their molten ore?
Lithium, potassium, calcium, sodium, magnesium and aluminium
5. Zinc is extracted from zinc(ii) oxide by heating with carbon. The ionic
equation for this reaction is shown below.
zinc (ii) oxide + carbon  zinc+ carbon dioxide
Zn2+O2- (s) + C (s)  2Zn (s) +
CO2 (g)
6. In question 5:
a) Which element is reduced? zinc (Zn2++ 2e’  Zn) as it has gained
electrons
b) Which element is oxidised? Oxygen (O2-  O2 +2e’) as it has lost
electrons
7. Electrolysis is the decomposition of an electrolyte (a molten or aqueous
compound that conducts electricity) using electricity. Complete the following
table:
Electrolyte
Product at anode
Product at cathode
(+)
(-)
Molten sodium chloride
bubbles of chlorine
sodium
Aqueus sodium chloride
bubbles of chlorine
sodium
Molten aluminum oxide
bubbles of oxygen
aluminium
Aqueous potassium bromide
bubbles of bromine
potassium
8. Look at this diagram for the electrolysis of aluminium oxide and answer the
questions that follow:
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Page 8 of 19
17-Mar-16
National 4 & 5 Chemistry
Metal Chemistry, Electricity & Chemistry,
Examples Answers
a) What is the product at the anode? Bubbles of oxygen gas.
b) What is the product at the cathode? Molten Aluminium metal
c) The anode is made of carbon and burns away (needing to be constantly
replaced). What is the product of this burning? Carbon dioxide
9. Here is a diagram to show the metallic structure of aluminium:
a) Define what a metallic bond is. Metallic bonding is the electrostatic attraction
between the positively charged atomic nuclei of metal atoms and the delocalised
electrons in the metal.
b) Explain in terms of structure and bonding why a metal like aluminium has:
i)
a high melting point - The electrostatic attraction between the positive ions and
the delocalised electrons acts in all 3-dimensions, strongly holding the lattice
together. Most metals have high melting and boiling points.
ii)
is relatively strong in tension - apply a force to (something) which tends to stretch
it. The electrostatic attraction between the positive ions and the delocalised
electrons acts in all 3-dimensions, strongly holding the lattice together. The
metal ions can move position, as do the sea of electrons and so allows
eventually for the metal to stretch.
iii)
is a good conductor of electricity - Metals are good conductors of heat and
electricity. This is due to the presence of the delocalised electrons.
iv)
is malleable (easily shaped) - During reshaping the metal ions move position, as
do the sea of electrons. The metallic bonding is not affected.
N4/5
PERCENTAGE COMPOSITION
N4/5
Find the percent compositions of all of the elements in the following compounds:
1)
CuBr2
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Page 9 of 19
17-Mar-16
National 4 & 5 Chemistry
Metal Chemistry, Electricity & Chemistry,
Examples Answers
Cu: 28.41%
Br: 71.59%
2)
NaOH
Na: 57.50%
O: 40%
H:2.50%
3)
(NH4)2S
N: 41.18%
H: 11.76%
S: 47.06%
4)
N2S2
N: 30.43%
S: 69.57%
5)
KMnO4
K: 24.68%
Mn: 34.81%
O: 24.68%
6)
HCl
H: 2.74%
Cl: 97.26%
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Page 10 of 19
17-Mar-16
National 4 & 5 Chemistry
7)
N:
18.
85
Metal Chemistry, Electricity & Chemistry,
Examples Answers
Mg(NO3)2
(a) Cu2+
Mg: 16.50%
+
2e-
Cu
reduction
%
O: 64.65%
8)
(NH4)3PO4
N: 28.19%
H: 8.05%
O: 42.95%
P: 20.81%
9)
Al2(SO4)3
Al: 15.79%
S: 28.07%
O: 56.14%
N5
OXIDATION & REDUCTION
N5
1.
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Page 11 of 19
17-Mar-16
National 4 & 5 Chemistry
(b) Br2
Metal Chemistry, Electricity & Chemistry,
Examples Answers
+
2e-
2 Br-
reduction
(c) Al
Al3+
+
3e-
oxidation
(d) Fe2+
Fe3+
+
e-
oxidation
(e) Cu2+
+
e-
Cu+
reduction
(f)
+
O2 + 4e-
4OH-
reduction
+
H2O
SO42-
2 H2O
(g) SO32-
+ 2H+
+2e-
oxidation
2.
(a)
Ca(s)
+
Ca oxid
(b)
Cl2(g)
Zn(s)
+
4 Al(s)
Al oxid
(e)
3 Mg(s)
Mg oxid
(f)
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+
Ni(s)
2 K+(aq) +
2 Br-(aq)
2 K+(aq) +
2 Cl-(aq)
+
Br2(l)
Zn2+(aq) +
SO42-(aq)
+
H2(g)
+
2 Fe(l)
Br- oxid
+
Zn oxid
(d)
Ca2+(aq) +
2 Cl-(aq)
Ni2+ red
Cl2 red
(c)
Ni2+(aq) +
2 Cl-(aq)
2 H+(aq) +
SO42-(aq)
H+ red
+
3 O2(g)
2 (Al3+)2(O2-)3(s)
O2 red
+ (Fe3+)2(O2-)3(s)
3 Mg2+O2-(s)
Fe3+ red
The spectator ions are shaded.
Page 12 of 19
17-Mar-16
National 4 & 5 Chemistry
N5
1.
2.
Metal Chemistry, Electricity & Chemistry,
Examples Answers
N5
ELECTROCHEMICAL SERIES RULE 1
potassium; sodium; magnesium; aluminium; iron; nickel; tin; lead;
copper; gold.
Filter paper
soaked in salt
solution.
(a)
Order
METAL A
voltmeter
METAL B
1
calcium
silver
2
zinc
tin
3
gold
silver
4
nickel
iron
5
copper
copper
METAL A
METAL B
(b) Copper and copper pairing would give a reading of 0 V.
(c) Platinum is poorer than gold at giving away electrons. If metal B
was platinum:
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(i)
which metal from the metal A list would give the largest
voltage? Answer calcium.
(ii)
which metal from the metal A list would give the smallest
voltage? Answer gold.
Page 13 of 19
17-Mar-16
National 4 & 5 Chemistry
ELECTROCHEMICAL SERIES RULE 2
DISPLACEMENT
N4
1.
Metal Chemistry, Electricity & Chemistry,
Examples Answers
N4
Use the electrochemical series to predict if a displacement reaction will take place.
Solution
Displacement
(yes / no)
nickel(II) chloride
yes
zinc chloride + nickel
(b) calcium
copper(II) sulfate
yes
calcium sulfate + copper
(c)
zinc
magnesium
sulfate
no
(d) lead
mercury(II)
nitrate
yes
lead(II) nitrate + mercury
magnesium chloride + tin
Metal
(a)
zinc
Products of Reaction
(e)
magnesium tin(II) chloride
yes
(f)
copper
copper(II) iodide
no
silver nitrate
no
(h) magnesium sulfuric acid
yes
magnesium sulfate +
hydrogen
(i)
aluminium chloride +
hydrogen
(g) gold
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aluminium
hydrochloric acid
yes
gold
nitric acid
no
Page 14 of 19
17-Mar-16
National 4 & 5 Chemistry
Metal Chemistry, Electricity & Chemistry,
Examples Answers
ELECTROCHEMICAL SERIES RULE 2
DISPLACEMENT
N4
N4
2.
(a)
zinc
Zn(s)
+
+
nickel(II) chloride
NiCl2(aq)
zinc chloride
ZnCl2(aq)
+
+
nickel
Ni(s)
(b)
calcium
Ca(s)
+
+
copper(II) sulfate
CuSO4(aq)
calcium sulfate
CaSO4(aq)
+
+
copper
Cu(s)
zinc
+
magnesium
sulfate
lead
+
Pb(s)
+
mercury(II)
nitrate
Hg(NO3)2(aq)
magnesium
+
tin(II) chloride
Mg(s)
+
SnCl2(aq)
copper
+
copper(II) iodide
gold
+
silver nitrate
magnesium
+
sulfuric acid
Mg(s)
+
H2SO4(aq)
aluminium
+
hydrochloric acid
Al(s)
+
6 HCl(aq)
gold
+
nitric acid
(c)
(d)
(e)
(f)
(g)
(h)
(i)
(j)
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No reaction, zinc cannot displace
magnesium from a solution.
lead(II) nitrate
+
mercury
Pb(NO3)2(aq)
+
Hg(l)
+
tin
+
Sn(s)
magnesium
chloride
MgCl2(aq)
No reaction, copper cannot
displace itself from a solution.
No reaction, gold cannot displace
silver from a solution.
magnesium
sulfate
MgSO4(aq)
aluminium
chloride
2 AlCl3(aq)
+
hydrogen
+
H2(g)
+
hydrogen
+
3 H2(g)
No reaction, gold cannot displace
hydrogen from an acid.
Page 15 of 19
17-Mar-16
National 4 & 5 Chemistry
Metal Chemistry, Electricity & Chemistry,
Examples Answers
N5
N5
WRITING REDOX EQUATIONS
1.
Zn(s)
Zn2+(aq)
+
2 e-
Each reaction
involves 2
electrons
which cancel.
Pb2+(aq)
+
2 e-
Pb(s)
Zn(s)
+
Pb2+(aq)
Zn2+(aq)
+
Pb(s)
REDOX
Fe(s)
Fe2+(aq)
+
2 e-
e-
Ag(s)
Multiply the
silver reaction
by 2.
Fe(s)
Fe2+(aq)
+
2 e-
Each reaction
involves 2
electrons
which cancel.
2.
Ag+(aq)
+
2 Ag+(aq)
+
2 e-
2 Ag(s)
Fe(s)
+
2 Ag+(aq)
Fe2+(aq)
+
2 Ag(s)
Li(s)
Li+(aq)
+
e-
3 e-
Al(s)
Multiply the
lithium
reaction by 3.
3 Li(s)
3 Li+(aq)
+
3 e-
Each reaction
involves 3
electrons
which cancel.
3.
Al3+(aq)
+
REDOX
Al3+(aq)
+
3 e-
Al(s)
3 Li(s)
+
Al3+(aq)
3 Li+(aq)
+
Al(s)
REDOX
Al(s)
Al3+(aq)
+
3 e-
2 e-
H2(g)
Multiply the
aluminium
reaction by 2,
the hydrogen
by 3.
2 Al(s)
2 Al3+(aq)
+
6 e-
Each reaction
involves 6
electrons
which cancel.
+
3 H2(g)
4.
2H+(aq)
+
6 H+(aq)
+
6 e-
3 H2(g)
2 Al(s)
+
6 H+(aq)
2 Al3+(aq)
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Page 16 of 19
REDOX
17-Mar-16
National 4 & 5 Chemistry
Metal Chemistry, Electricity & Chemistry,
Examples Answers
N5
N5
WRITING REDOX EQUATIONS
5.
Fe3+(aq)
+
Mg(s)
Mg2+(aq)
3 e-
Fe(s)
3 Mg(s)
3 Mg2+(aq)
+
2 e-
Multiply the
magnesium
reaction by 3,
the iron by 2.
+
6 e-
Each reaction
involves 6
electrons
which cancel.
2 Fe3+(aq)
+
6 e-
2 Fe(s)
3 Mg(s)
+
2 Fe3+(aq)
3 Mg2+(aq)
+
3 Mg2+(aq)
Cu(s)
Cu2+(aq)
+
2 e-
e-
Au(s)
Multiply the
gold reaction
by 2.
Cu(s)
Cu2+(aq)
+
2 e-
Each reaction
involves 2
electrons
which cancel.
6.
Au+(aq)
+
REDOX
2 Au+(aq)
+
2 e-
Au(s)
Cu(s)
+
2 Au+(aq)
Cu2+(aq)
+
Au(s)
Na(s)
Na+(aq)
+
e-
2 e-
2 Br-(aq)
Multiply the
sodium
reaction by 2.
2 Na(s)
2 Na+(aq)
+
2 e-
Each reaction
involves 2
electrons
which cancel.
7.
Br2(l)
+
REDOX
Br2(l)
+
2 e-
2 Br-(aq)
2 Na(s)
+
Br2(l)
2 Na+(aq)
+
2 Br-(aq)
REDOX
Al(s)
Al3+(aq)
+
3 e-
2 e-
2 I-(aq)
Multiply the
aluminium
reaction by 2,
the iodine by 3.
2 Al(s)
2 Al3+(aq)
+
6 e-
Each reaction
involves 6
electrons
which cancel.
+
6 I-(aq)
8.
I2(s)
+
3 I2(s)
+
6 e-
6 I-(aq)
2 Al(s)
+
3 I2(s)
2 Al3+(aq)
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Page 17 of 19
REDOX
17-Mar-16
National 4 & 5 Chemistry
Metal Chemistry, Electricity & Chemistry,
Examples Answers
N5
WRITING REDOX EQUATIONS
N5
1.
METAL A
METAL B
DIRECTION OF THE ELECTRON FLOW
lead
aluminium
From aluminium to lead
copper
gold
From copper to gold
nickel
magnesium
From magnesium to nickel
tin
copper
From tin to copper
silver
lead
From lead to silver
gold
iron
From iron to gold
calcium
zinc
From calcium to zinc
2.
(a)
Al(s)  Al3+(aq) + 2e-
Al is oxidised.
Pb2+(aq) + 2e-  Pb(s) Pb2+ is reduced.
(b) Cu(s)  Cu2+(aq) + 2e-
Cu is oxidised.
Au+(aq) + e-  Au(s) Au+ is reduced.
(c)
Mg(s)  Mg2+(aq) + 2e-
Mg is oxidised.
Ni2+(aq) + 2e-  Ni(s) Ni2+ is reduced.
(d) Sn(s)  Sn2+(aq) + 2e-
Sn is oxidised.
Cu2+(aq) + 2e-  Cu(s) Cu2+ is reduced.
(e)
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National 4 & 5 Chemistry
N5
Metal Chemistry, Electricity & Chemistry,
Examples Answers
WRITING REDOX EQUATIONS
2.
(e)
Pb(s)  Pb2+(aq) + 2e-
N5
Pb is oxidised.
Ag+(aq) + e-  Ag(s) Ag+ is reduced.
(f)
Fe(s)  Fe2+(aq) + 2e-
Fe is oxidised.
Au+(aq) + e-  Au(s) Au+ is reduced.
(g) Ca(s)  Ca2+(aq) + 2e-
Ca is oxidised.
Zn2+(aq) + 2e-  Zn(s) Zn2+ is reduced.
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