Determine the theoretical and percent yield of hydrogen gas if 70.0 g water undergoes electrolysis to produce hydrogen and oxygen and 2.69 g hydrogen is collected.
Answers
Explanation:
gWhen two moles of water are exposed to electric current, the molecules of water are split into two moles of hydrogen gas and one mole of oxygen gas. This reaction is a decomposition reaction of water molecules.
Answer and Explanation:
Given Data
The mass of water is
78
g
.
The actual yield of hydrogen gas is
3.02
g
.
The balanced chemical equation of the reaction is given as follows.
2
H
2
O
→
2
H
2
+
O
2
The number of moles can be determined by the formula given as follows.
N
u
m
b
e
r
o
f
m
o
l
e
s
=
M
a
s
s
M
o
l
a
r
m
a
s
s
.
.
.
(
1
)
Since the molar mass of water is
18
g
/
m
o
l
.
Substitute the respective values in equation (1) given above.
M
a
s
s
o
f
H
2
O
=
78
g
18
g
/
m
o
l
=
4.33
m
o
l
From the balanced chemical equation, 2 moles of water give 2 moles of hydrogen gas.
So, 4.33 moles of water will give 4.33 moles of hydrogen gas.
Therefore, the number of moles of hydrogen gas is 4.33 mol.
Since the molar mass of hydrogen gas is
2
g
/
m
o
l
.
Substitute the respective values in equation (1) given above.
4.33
m
o
l
=
M
a
s
s
2
g
/
m
o
l
M
a
s
s
=
4.33
m
o
l
×
2
g
/
m
o
l
=
8.66
g
Therefore, the theoretical yield of the hydrogen gas is 8.66 g.
The percent yield can be determined by the formula given as follows.
P
e
r
c
e
n
t
y
i
e
l
d
=
A
c
t
u
a
l
y
i
e
l
d
T
h
e
o
r
e
t
i
c
a
l
y
i
e
l
d
×
100
.
.
.
(
2
)
Substitute the respective values in equation (2) given above.
P
e
r
c
e
n
t
y
i
e
l
d
=
3.02
g
8.66
g
×
100
=
34.87
%
Therefore, the percent yield of the hydrogen gas is
34.87
%
.