What mass of copper hydroxide is precipitated by using 200 gm of sodium hydroxide?
Answers
Answer:
Explanation:
An alternative approach is to simply use the mole ratios that exist between the species that take part in the reaction, then use the molar mass of copper(II) hydroxide,
Cu
(
OH
)
2
, to get the mass formed by the reaction.
So, your sodium hydroxide solution contains
C
=
n
V
⇒
n
=
C
⋅
V
n
O
H
−
=
0.450 M
⋅
100
⋅
10
−
3
L
=
0.0450 moles OH
−
The net ionic equation for this double replacement reaction looks like this
Cu
2
+
(aq]
+
2
OH
−
(aq]
→
Cu
(
OH
)
2(s]
⏐
⏐
↓
So,
2
moles of hydroxide ions will react with one mole of copper(II) ions and form one mole of copper(II) hydroxide.
This means that the reaction will produce
0.0450
moles OH
−
⋅
1 mole Cu
(
OH
)
2
2
moles OH
−
=
0.0225 moles Cu
(
OH
)
2
To find how many grams of copper(II) hydroxide will contain this many moles, use the compound's molar mass
0.0225
moles OH
−
⋅
97.56 g
1
mole OH
−
=
2.195 g Cu
(
OH
)
2
Rounded to three sig figs, the answer will be
m
C
u
(
O
H
)
2
=
2.20