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USA Physics and Chemistry Contests
National Chemistry Olympiad
2008 National Chemistry Olympiad
11
11
Part of
2008 National Chemistry Olympiad
Problems
(1)
2008 USNCO Local #11: Moles of X, Y and Z
Source:
12/17/2012
For the reaction:
2
X
+
3
Y
→
3
Z
2X + 3Y \rightarrow 3Z
2
X
+
3
Y
→
3
Z
, the combination of
2.00
2.00
2.00
moles of
X
X
X
with
2.00
2.00
2.00
moles of
Y
Y
Y
produces
1.75
1.75
1.75
moles of
Z
Z
Z
. What is the percent yield of this reaction?
<
s
p
a
n
c
l
a
s
s
=
′
l
a
t
e
x
−
b
o
l
d
′
>
(
A
)
<
/
s
p
a
n
>
43.8
%
<
s
p
a
n
c
l
a
s
s
=
′
l
a
t
e
x
−
b
o
l
d
′
>
(
B
)
<
/
s
p
a
n
>
58.3
%
<
s
p
a
n
c
l
a
s
s
=
′
l
a
t
e
x
−
b
o
l
d
′
>
(
C
)
<
/
s
p
a
n
>
66.7
%
<
s
p
a
n
c
l
a
s
s
=
′
l
a
t
e
x
−
b
o
l
d
′
>
(
D
)
<
/
s
p
a
n
>
87.5
%
<span class='latex-bold'>(A)</span>\hspace{.05in}43.8\%\qquad<span class='latex-bold'>(B)</span>\hspace{.05in}58.3\%\qquad<span class='latex-bold'>(C)</span>\hspace{.05in}66.7\%\qquad<span class='latex-bold'>(D)</span>\hspace{.05in}87.5\%\qquad
<
s
p
an
c
l
a
ss
=
′
l
a
t
e
x
−
b
o
l
d
′
>
(
A
)
<
/
s
p
an
>
43.8%
<
s
p
an
c
l
a
ss
=
′
l
a
t
e
x
−
b
o
l
d
′
>
(
B
)
<
/
s
p
an
>
58.3%
<
s
p
an
c
l
a
ss
=
′
l
a
t
e
x
−
b
o
l
d
′
>
(
C
)
<
/
s
p
an
>
66.7%
<
s
p
an
c
l
a
ss
=
′
l
a
t
e
x
−
b
o
l
d
′
>
(
D
)
<
/
s
p
an
>
87.5%
percent