Chern 1A Test 2
Sept. 16, 2005
Show all work. Also take care in propagating uncertainty via sig. figs.
1. Gasoline is a complex mixture of hydrocarbons of which one component is the hydrocarbon nonane,
C9Hzo•
a.
Write a balanced chemical equation for the complete combustion ofnonane.
If
b.
I
+-
0:1-
In your own words, give the submicroscopic (molecular scale) meaning of the balanced
wdL /1f~1
~,quati~~
f~rJjctJ~~
.
/
J
.
Now give the macroscopic (laboratory scale) meaning of the balanced reaction ..
tif ~
J~
~#'~
If)
~
c.
4~
~
~
/ ~ 1uJ-.~
a.s-J
/l./ ~
'5 ~
/0 ~
Oj~.
~ ~
2. A solution is prepared by dissolving 2.50 g NaCI in 550.0 g H20. The density of the resulting solution
is 0.997 g/mL. What is the molarity of NaCI in the solution? Hint: The volume is not 550.0 mL! .
~
:= ~
A~
~
~
II
-
.
i!ACI T ~
Jr+#-
vA." ~~
-::=-
1-
5 Slf . .2 luL
0.77':; ~L.<
50 ~
"f-
--_--~
[0 ,. onJ-. M.
~
S 6-. '-/1./
7-
\
L
) ~ If )...
A chemist wanted to prepare hydrazine, N2~, (a type of rocket fuel) by the reaction:
2NH3 + ocr 7 NzH4 + cr + H20. To do this she mixed 3.0 mol NH3 with 2.0 mol ocr.
CJr
3.
55' -Z. ~
-=-
:S5!,~,
==
- ,""',;'&
/J1~ ;U L(
--~--::::'
NJ-()
What is the limiting reactant?
b.
How many moles of hydrazine will be obtained?
S. 0
c.
~
JJ
I~) y \?-.~
~
~
3 . '2...,
Z. \
a.
~~Jl2\ ~
Nt~::!.
-
~")
/, ~
Mr(
What is the excess reactant and how many moles remain?
ls
}J
t-I(
~3
;U~!J'-/
4.
The attitude control rockets on the space shuttle use the hypergolic rocket fuel monomethyl hydrazine (CN2H6 or
CH3NHNH2) with dinitrogen tetroxide (an oxidizer). Hypergolic fuels spontaneously ignite upon contact. In this
case the reaction products are nitrogen, carbon diof.:ide,an" w~ter.
l{
l,~'\-;-\ ~ ~
Write a balanced chemical equatirt!0r
_.L
a.
the reaction.
+ ~ jJ~O 'f ~ ~. / AJ,-
CAJ"J-H 6
09)..~oo
fqg
19,
I 0/7(
0k~I0;t/5,0
0fI. 1s
:26,07
f~s
~,
/()
J
O. j
(;99'.
r-
(O~ + (~fI,-O
tf
each product?
'
e um g reactant? And what is the mass (theoretical yield) of
b.
Given 1.00 kg each reactant which is th r ·tin
10.
t"1
:J..
Q. S~{O~ 0 :J
./-./f7!
. ()
00
'S
.J
tf'::rq
~ ;0 ..67-
LfLff
g-f
,
5,
J
A 0.578 g sample of pure tin (Sn) is reacted with gaseous fluorine until the mass of the resulting
compound is constant at a value of 0.944g. Determine the empirical
formed from the mass data ..
~
'
~ ( O. 9 Cf
S C1 -- 1(5.71
o. ~7~)-rJv(·---:::
~
0, ~ G6 Y
~, {} F.--- -I,
00
6.
formula of the ~
tf - (J. ~728" )
__ ().
C)
/93
--:> V\
_3 b {; }-
r
"1:::.'
't
>~«76
~
J in the
9(s-v{
Suppose you have a job
ianey chemistry
stockroom and your boss asks you to prepare 2.0000 L
of a 0.250 M solution of ammonium sulfate. Assume you have an analytical balance and 2.0000L,
't
in CJ
detail
VI N Describe
<f)J- ~
1.0000L,
500.00mL,
fl?ks.
how
you would
makeand
this250.00mL
solution.~volumetric
•.••••
'fO~li~
~
stW7l'f)~
:=
:<.oooo!- ~ o. JS0
r
(3amounts
2., 13 Q'
"/~ ()
If
with the f'1
correct
1!.
I<
I!.~.' 3/;{ :: (,6. (J
1~
w(v.;4 n(
PItH-€. b G, I
W U'fL ~0'( ;"
:2.,0 DOO L
,
f
"
0.0 u-l I /-. crl. 01 II;.. 0
7J.e
DrSSo1v{"''''
\
Vo(u
~
to 2.~0 £)"tJO
afJ
Wl/;(
Vie"tf ~
Q
CJ
b.
hrr ~
VI
L
tv' {- V.f-
'=
M
~\
V"
l
i-G
'-=,
~
~
"'fv\
~"
i~
.
_
\J{- ~
l SOO.
0 000
0 00 M
("\{- - 0 ~).~ 0
J-' 0 0 otL
O~)..SO¥..
( 000
00
L
L
"J
IP"'v--
0
cJ1
-0
(v\; K
f
~00 ()
Ivvdi
(&Ok,
1k
\J::: /_ 0 00 0
starting with a stock solution which is 1.000 M in ammonium sul~ate ..•...
Mt V(
~
~.
, Ie.
00 If rs--:; i'~
f2
fluoride
Y\
{-
~ 0~S 00
M s;fc)c
k ~
L
eP;
.
IJte
L
7.
Balance each of the following reactions including subscripts for the phases (assuming aqueous
solutions when appropriate). Use solubility rules if needed. Also classify the reactions in as many
ways as possible.
a..l..Na
+ ..2-H20
\S)
7l..NaOH
~Jl)
+
r~~ / ~CLt
H2
(f)
~~)
<;."(
+).<"02 7//'C02
b.l.CsHls
(7)
(? )
(,1.)
+{YfIzO
COM
IJ(e
bu::,7;o ''''.. )
(7)
Jas.
c.. Sr(OHh
+2..HN03
7
Na2S04 +
(elf)
Ba(N03)2 7
~f)
i~)
re-t Co.( e ",.0.71 ,
rd
of )
I-cYW';~
Sr(N03)2 +~H20
~t)~g)
d.
~'r'rv-
@()
BaS04
\S)
(e)
+2.. NaN03
(~t)
f
I--e- (
if' •.t,,,f: 0<1
)
(f,~Me J-~/~ten-4,
e. )..Na
(~ )
+
Ch 7,2.NaCI
(Cj')
Cs )
,
-- --- ---
I
8.
Extra: Suppose in this week's sodium bicarbonate decomposition experiment you forgot to read the
instructions and used intense heat instead of moderate heat so that the following reaction went almost
to completion:
k \1\:;::.
.
2NaHC03 -7 Na20 + H20 + 2COz
~
Also suppose you started with 0.8791 g o~~C~
a.
Calculate the theoretical yield o~
~-~
~
f,'/'
~
f'A-
ro; -;,
I'"
t-'\
-=--
r~
'f ,0'
I
b
a.
,-'
8'
91'
'11vt1.
U
;;xi7,(~~
y ~ ~ q'3JD
~ 't J
(J • 'is
. 7-'7 f 5 /11,,1/(07 .•.'6~.
I f<f " J..b
1/5'4./I(OJ/(
..J. )Jq
)It> (f
,...0
(03 -{.
9&
b. Suppose you actually ended up with 0.420 g product. Calculate the percent yield Na20 in
grams.
CL<{U".,(
--.
1-h~·)(.tN
i:0 J -{:I
O.1:.i; 7-0
~
'
11
1
~
0
0
\
::=
...
,-1..1
0(.1::
c.
True percent yields are always less than or equal to 100%. Is there a discrepancy here? Can you
f)
I:
exp'6
&;J n=t ~ ~
7ti.- ~
~w<-~~~~~
(0~ I
A;l ~
~
lI..
b\
)J G.:L U:)3,
"
I
o.-vJ)J tI ~(:)
r"-'