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Page 1

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Lesson
4


Reac0ons
of
Group
2
metals





Objec0ves


· Describe
the
reac0ons
of
group
two
metals


· Write
half
equa0ons
for
the
reac0on
of
group
2

metals
with
oxygen
and
water



· Describe
the
reac0ons
of
group
two
metal
oxides


· Describe
the
reac0ons
of
group
two
metal

hydroxides…

Page 2

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Reac%vity
of
group
2
elements



Group
2
elements
are
strong
REDUCING
agents



When
they
react
they
are
OXIDISED



OIL
­
RIG



M

M2+

+
2e-




Predict
the
trend
in
reac0vity
going
down
the
group





Reac%on
with
oxygen

2Ca(s)
+
O2(g)












2CaO(s)






What
are
the
oxida0on
numbers
for
each

element…

Page 3

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Reac%on
with
water

Ca(s)
+
2H2O(l)













Ca(OH)2
(s)
+H2(g)






What
are
the
oxida0on
numbers
for
each

element
before
and
aUer
the
reac0ons?






Group
2
oxides
and
hydroxides
are
bases
and


neutralise
acids.
When
dissolved
in
water
they

have
a
high
pH
(10-11)





MgO(s)

+
2HCl
(aq)



MgCl2
(aq)
+…

Page 4

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AfL

When
you
dissolve
MgO
in
water
it
has
a
high

pH.
Explain
why
this
is?





Answer

To
have
a
high
pH
there
must
be
hydroxide
ions

present.




When
MgO
is
dissolved
in
water
it
reacts
with

the
water
to
produce
Mg(OH)2



MgO(s)
+
H2O(l)

Mg(OH)2
(aq)







4

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Past
paper
ques0on





Past
paper
ques0on





5

Page 6

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Past
paper
ques0on





Past
paper
ques0on






6

Page 7

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Mark
scheme





Group
2
carbonates



Thermal
decomposi0on
by
heat
­
more
difficult

going
down
the
group



MgCO3(s)














MgO
(s)
+
CO2
(g)



In
other
words
THERMAL
STABILITY
increases
as

you
go
down
the
group.







7

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Past
paper
ques0on





Past
paper
ques0on





8

Page 9

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Mark
scheme





Past
paper
ques0on





9

Page 10

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Mark
scheme





How
to
write
"half-equa0ons"



A
half
equa0on
shows
the
reagent
being
oxidised


OR
the
reagent
being
reduced
separately.



It
shows
what
is
happening
to
the
electrons



Ca


Ca2+
+
2e-




O2
+
4e-

2O2-



Afempt
the
half
equa0on
for
the
the
reac0on
of

Ca
with
H2O





10

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