amc
_
Date
_
Stoichiometry
So far in your chemistry course, you have learned that chemists count quantities
f lem nts and compounds in terms of mol s and that th y relate moles of a
substance to mass by using the molar mass. In addition, you have I am d to
write chemical equations so that they represent the rearrangements of atoms that
take place during chemical rea -lions, and you have learned to balance these
quations. In this chapter you will be abI to put these separate skills together to
a 'omplish one of the most important tasks of 11 mi try-using ch mical equa­
tions to make pr dicti ns about the quantities of substances that react or are
given off as product and relating those quantities to one another. This process of
relating quantities of reactants and products in a chemical reaction to one
another is called sto?~ch'iometry.
First, look at an analogy.
Suppo you n~ed to make several sandwiches to tak on a pi nic with
friends. Y;. u de ide to mak turkey-ancl- heese sandwiches using the foUowing
"equation:"
2 br ad slic s
+ 2 turkey slices
+ 1 lettuce leaf + 1 hee . slice
~ 1 turkey-and-cheese sandwi h
This equation shows that you need tho e ingredients in a ratio of 2: 2: 1: 1,
resp cHv ly. Y; u can use this equation to predict that you would n d' 0 turk Y
slices to make 15 sandwiches or 6 ch es . slices to go with 12 turkey slices.
Zinc reacts with oxygen accor~g to the following balanced chemical equa­
lion:
2Zn +'02
~
2ZnO
Like the sandwich recipe, this equation can be viewed as a "recipe" for zinc
oxid . It t Us you that reacting two zinc atoms with a mol cule of oxygen will
produ('e tw formula units of zinc oxide. Can you predict how many zinc oxide
units could be formed from 500 zinc atoms? Could you determine how many
moles of oxygen molecuJf's it would take to react with 4 mol of zinc atoms? What
if you had 22 g of zinc and wanted to lmow how many grams of ZnO could be
made from it? K ep in mind that the chenucal equation relates amounts, not
masses, of pro ucts ;md r actants. Th problems in this chapter will show you
how to solve problems of this kind.
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Holt ChemFile: Problem-Solving Workbook
97
Stoichiometry
Name
_ Class
_ Oat
I Problem Solving continued
General Plan for Solving Stoichiometry Problems
Mass of
substance A
Convert using
the molar mass
of A.
Amount in
mol of
substance A
•
•
Convert using the
mole ratio~, given in the
balanced chemical equation.
Amount in
mol of
substance B
Convert using
the molar
mass of B.
Mass of
substance B
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Holt ChemFile: Problem-Solving Workbook
98
Stoichiometry
I Problem Solving continued
Sample Problem 1
Ammonia is made industrially by reacting nitrogen alld hydrogen under
pressure, at high temperature, and ill the presence of a catalyst. The
equation is Nz(g) + 3H 2 (g) ~ 2NH3 (g). If 4.0 mol of H 2 react, how many
moles of NH3 will be produced?
Solution
ANALYZE
What is given in the probl m?
the balanced equation, and the amount of Hz in
moles
What are you asked to find?
the amount of NBa produced in moles
Organization of data is extr mely important in dealing with stoichiometry prob­
lems. y: u will find that it is rna t he]pfulto make data tables such as the follow­
ingone.
Items
Data
Substance
Hz
NlI3
3
2
Molar l1a s
NA*
NA
Amolillt
4.0 mol
? mol
oefficient in balanced equation
Mass of sub tance
A
A
"N. means not applicable to the problem
. PLAN
What steps are need d to calculate the amOlmt of NH; that can be produc d from
4.0 mol H2 ?
Multiply by the mole ratio of NHa to Hz determined from the coefficients of the
balanced eq nation.
fJ
Amount of
H2 in mol
- - - - - - - - i..~
mlllliPIYhymOleralio·!!ft-
II
Amount of
NH 3 in mol
mole raliu
gil-en
2 mol NH
mol H) x
] = mol
3 mol H2
H]
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Holt ChemFile: Problem-Solving Workbook
99
Stoichiometry
arne
_
Glass
_ Date
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I Problem Solving continued
COMPUTE
~.)- X
4.0 1
2molNH
~~t--t:f
3~HZ
=
2.7 mol NH3
EVALUATE
Are the units cOlTect?
Yes; the answer has the correct unit of moles NHa.
Is the number of significant figures orr ct?
Yes; two significant figures is correct because data were given to two significant
figures.
Is the answer reasonable?
Yes; the answer is 2/3 of 4.0.
Practice
1. How many moles of sodium will react with wat r to produce 4.0 mol of
hydrogen in the following reaction?
2 a(s) + 2HzO(l)
--?
2 aOH(nq) + Hz(g) ans: 8.0 mol Na
2. How many moles of lithium chloride will be formed by th reaction of chlo­
rine with 0.046 mol of lithium bromide in the following reaction?
2LiBr(aq)
+ CI 2 (g) ----72LiCl(aq) + "Br2(l) ans: 0.046 mol Lie]
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Holt ChemFile: Problem-Solving Workbook
100
Stoichiometry
amc
I Problem Solving continued
3. Aluminum will react with ulfuric acid in the following reaction,
2Al(s)
+ 3H2 S04 (l) ~ Al 2(S04}3(aq) + 3H2 (g)
a. How many moles of H2 S04 Mll react with 18 mol AI? ans: 27 mol H 2 S04
b. How many moles of ach product will be produ ed', ans: 27 mol Hz, 9 mol
Al 2 ( S04)3
4. Propane burn in excess oxyg n a 'cording to the following reaction.
C3 H s + 50 2
~
3C02 + 4H2 0
a. How many moles each of CO 2 and H20 are formed from 3.85 mol of
pr pane? ailS: 11.6 mol CO 2 , 15.4 mol H2 0
b. If 0.647 mol of oxygen is used in the burning of propane, how many moles
each of C :. . and II2 ar produced? How many moles of C3 H8 are con­
sumed? an : 0,388 mol CO 2 , 0.518 mol H 2 0, 0,129 mol C3 H s
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<i)
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Holt ChemFile: Problem-Solving Workbook
101
Stoich iometry
Name
_
Class
_ Dat
I Problem Solving continued
Sample Problem 2
Potassium cWorate is sometimes decomposed in the laboratory to gener­
ate oxygen. The reaction is 2KCIO:l(s) ----? 2KCl(s) + 30 2 (g). What mass
of KCI0 3 do you need to produce 0.50 mol 0 2 ?
Solution
ANALYZE
What i given in the pro lem?
the amount of oxygen in moles
What are you asked to find?
the mass of potassium chlorate
Items
Data
Substance
KCI0 3
O2
2
3
Molar mass*
122.55 glmol
N
Am'unt
? mol
0.50 mol
Mass
?g
.
Coefficient in balanced equation
A
" determined from the periodic table
PLAN
What steps are needed to calculate the mass of K 103 ne ded to produce 0.50
mol02?
Use the mole ratio to convert amount of O2 to amount of KCI0 3 • Then onvert
amount of KCI0 3 to mass of KCIO s .
Il
f)
Amount of 02 in mol
multiply by mole ratio
2 mol Kc/(),
3 mol O!
Amount of KCI0 3 in mol
bYl
multiply
molar mass
oiKCIO,
II
Mass of KCI0 3 in 9
gl\('O
mol
mole ratio
molar mass KCIO!
2 mol KCl0 3 122.55 g KCIO,
) X 3 mol Oz X I mol KCIO, .
=g
KC 0
1 3
COMPUTE
~~t.-r\
O50
.' .!:.!Jkfl V2
X
2~
~ ~ t.<\
3 ~ V2
X
122.55 g KCI02
~ ~ 1 T2:Pt1"'\
1 ~.!J.\.u-rHJlV~3
-
-
41
g
KCIO
3
EVALUATE
Are the units
COlT
ct?
Yes; units canceled to give grams of KCI0 3 .
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Holt ChemFile: Problem-Solving Workbook
102
Stoichiometry
Name
------.-
_
Class
_
Date
_
I Problem Solving continued
Is the numb r of signili 'ant name correct?
Yes' two significant figures is conect.
Is Lh answer reasonable?
Yes; 41 g is about fa of the molar mass of KCIO a , and 0.5 x 2/3 = 113.
Practice
1. PhosphonLS burru in air to produce a phosphorus oxide in the following
reaction:
4P(s) + 50 2(,g) --7 P40 lO (S)
a. What mass of phosph rus will b needed to produce' .25 mol of PtO LO?
aIlS: 403 g P
b.lf 0.489 mol of phosphorus bums, what m 'S of' oxygen is us d? What mass
of P4 0 lO is produced. ans: 19.6 g O2 ,15.4 g P204
2. Hydrogen peroxide breaks down, releasin 6 oxygen, in the following rea 'non:
2II 20 2(aq) --72H2 0(l) + °2(,g)
a. What mass of oxygen is produ ed when 1.840 mol of Hz
aus: 29.44 g O2
2
decomposes?
b. What OIass of wat r is produced when 5.0 mol O2 i produced by this
reaction? ans: 180 g H2 0
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(i)
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Holt Ch mFile: Problem-Solving Workbook
103
Stoichiometry
I Problem Solving continued
Sample Problem 3
How many moles of aluminum will be produced from 30.0 kg Al2 0 a in he
following reaction?
Solution
ANAlYZE
What is given in the probl m?
the mass of aluminum oxide
What are you asked to find?
the amoWlt of aluminwn prodoced
Items
Data
Substance
Al;20;}
Al
Co flkient in baJan ed equation
2
4
Molar mass
101.96 glmol
Amount
?mol
? mol
Ma
30.0 kg
NA
A
PLAN
What steps are needed to calculate the amoUllt of AI produced from 30.0 kg of
Al 2 0 J ?
The molar mass of AI 2 0 3 can be used to convert to moles AI 2 0 g • The mole ratio
of AI:AI20 3 from the coefficients in the equation will convert to moles AI from
moles AI2 0 3 •
Mass of AlzO] in 9
"""'lio(f------- - -,,-
IOOO
Mass of A1z03 in kg
11II1IIifJl"I)I--~
mU!lip!y by the
I ~8
J.
il/\'crse of Ihe
molar mass of
Al.O,
1
Amount of AI 2 0 3
in mol
--------...)1
mll!lip!y by the mole ratio
II
Amount of AI in mol
4 mol Al
-" mol AI,O,
,1/,0 j
mole IIItiu
l mol AI,O:
4 mol AI
1Il0!ar mass
1000 g
"i1'cl1
kg AI] 0 X - - X
- d X
= mol At
\
kg
101.96 g AIPI
2 mol AL:P2
COMPUTE
. 0.0
~A
X
1000
~
gX
1~
101.96~
X
4 mol AI
2~
=
588 mol AI
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Holt ChemFile: Problem-Solving Workbook
104
Stoichiometry
lass
ame
_ Date
_
I Problem Solving continued
EVALUATE
Are the wtits correct?
Yes; units canceled to giv moles of AI.
Is lhe number of significanL figur
conect.
Yes; tlU'ee significant figures is corr ct.
I ~ th answer reasonable?
Ye ; th molar mass of Al2 0:j is about 100, 0 30 kg of Al2 0 3 is about 300 mol.
The mole ratio of AI:A1 2 0:J is 2: ,so the answer should be about 600 mol AI.
Practice
1. Sodium 'arbonate reacts with nitric add according to the following quation.
Na1C03(.s) + 2H 0;$ ~ 2NaNO:~ + CO2 + H~
a. How many mol of Naz 'O:~ are requir d l Pl' duce 100.0 g of aNO:3?
aus: 0.5 82 mol Na2COa
b. If 7. 0 g f
a2
O;~
reacts, how many moles of CO2 are produced? aos:
0.0708 mol CO2
2. Hydrog n i . generated by passing hot steam over iron, which oxidizes to form
Fe;Jn.J' in the following equaLion.
3Fe(s) + 4H 20(g) ~ 4II2 (y) + Fe3 4(S)
a. If 625 g of Fe;304 is produc cl in the reaction, how many mol s of hydrogen
are produced at Lh(~ . ame tim . ans: 10.8 mol H2
b. How many moles of iron would be needed t.o generate 27 g of hydrogen?
aDS:
10. mol Fe
CO!"Vliglll (1 I Y Holt, Rilwharl and Willslnll, ,<\]1
right~
Holt ChemFile: Problem-Solving Workbook
reserved.
105
Stoichiometry
anle
Class
_
_
Date
_
I Problem Solving continued
Sample Problem 4
Methane burns in air by the following reaction:
+ 20 2 (g)
CB 4 (g)
~
CO 2 (g)
+ 2H2 0(g)
What mass of water is produced by burning 500. g of methane?
Solution
ANALYZE
What is given in the problem?
the mass of methane in grams
What are you asked to find?
the mas of water produced
Items
Data
Substance
CI-l1
H2 O
Coefficient in balan ed equation
1
2
Molar mass
W.O. glmol
18.02 glmol
Amount
? mol
? mol
Mass
500. g
.g
PLAN
What st.eps are needed t.o calculate the mass of H2 0 produc d from the bLUuing
of 500. g of CH4 ?
Convert grams of CH4 to moles CH 4 by using the molar mass of CH4 • Use the
mole ratio from the balanced equation to determine moles H 2 0 from moles CRt.
Use the molar mass of H 2 0 to calculate grams H 2 0.
D
Mass of CH 4 in 9
mlll,iPIY by the
;llverse vf the
molal' mass of
.
CH,
I
fI
Amount of CH 4
in mol
--------)o~
mufliply by Ihe mule ratio
2 mol
11/101 ell l
Hp
IJ
Amount of H2 0 in mol
hY!
multiply
the maim
mass 011(0
II
Mass of H20 in 9
molar mil,)S CH,
mole ratio
molal' r/'lass H,O
1 mol CH.j
2 mol H 0
18.02 g H 2"O
. H 0
gH x.
X
• X
= g 1
.j
16.05 g CH.j
1 mol CH.j
1 mol Hp
~gci
l'e 11
Copyright
L
by Holt. Ritwhart and Willston.
II right.'5 reserved.
Holt ChemFile: Problem-Solving Workbook
106
Stoichiometry
lame
_
Class
_
Date
_
I Problem Solving continued
COMPUTE
f"H
•500 . jSX:>!l...l
rl
X
1~
rt
f"xf X
16.05 tyoJ..l4
2 ~ 18.02 g H2 0
~~~1.P'f::f X
~~~1~
1 !!J.urvu4
1 !!J.uruzO
=
1 12
•
X
10:1
H
g z
EVALUATE
Ar the units con-ect?
Yes; mass of H 2 0 was required, and units canceled to give grams H 2 0.
Is the number of signifi ant figure
'orrect?
Yes; three significant figures is correct because the mass of CH4 was given to
three significant figures.
Is the answer reasonable?
Yes; CH4 and H 2 0 have similar molar masses, and twi<le as many moles of H 2 0
are produced as moles CH4 burned. So, you would expect to get a little mor
than 1000 g of H 2 0.
Practice
1. Calculate the mas of ilv r bromide produced from 22.5 g of silv r nitrate in
the following reaction:
2AgN03 (aq)
+ MgBr2(aq) ----72AgBr(s) + Mg(N0 3 )2(aq) aus: 24.9 g AgBl'
2. What mass of acetylene, CzHz, will b produc d from the reaction of 90. g of
alciurn carbide, CaC z, with water in the following reaction?
CaC2 (s) + 2H2 0(l) ----7 zHz(g) + Ca(OH)z(s) aus: 37 g C2 H2
3. 'hlorine gas can be produced in the laboratory by adding concentrated
hydrochloric acid to manganese (IV) oxide in the folloWing reaction:
1n02(S) + 4IICl(aq) ----7 MnClz(a.q) + 2H zO(l + C1 2(g)
a. Calculate the ma.ss of MnO z n ed d to produce 25.0 g of C12 . ans: 30.7 g
Mn° 2
b. What mass of MnCl z is produced when 0.091 g of Cl z is generated?
ans: 0.16 g MnCI 2
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Holt ChemFile: Problem-Solving Workbook
107
Stoichiometry
arne
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lass
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I Problem Solving continued
Additional Problems
1. How many moles of anunonium sulfat can b made from the reaction of 30.0
mol of NH3 with H 2S04 ac ording to the following equation.
2NH3 + H2 S04
--')
(NHJ zS04
2. In a very violent r action call d a thermite reaction, aluminum metal reacts
with iron(ITI) oxide to form iron metal and aluminum xid according to the
following equation:
+ 2AJ --') 2Fe + Alz0 3
a. What mas of Al will react with 150 g of F Z03?
b. If 0.905 mol Al 2 0 3 L., produ 'ed in the reaction, what mass of F is pro­
duced?
F
203
c. How many moles of FezO:~ will react with 99.0 g of Al?
3. As you saw in ample Problem 1, the reaction :!.Cq) + 3H~(g) --') 2 I3 (g) is
used to proclu ammonia conunercially. If 1.40 g of N 2 are used in the reac­
tion, how many grams of Hz will be nf'eded?
4. What mass of sulfuric acid, H:!.S04, is required to r at with 1.27 g of potas­ sium hydroxid ,KGH? The products of this reaction are potassium sulfate
and water.
5. Ammonium hydrogen phosphate, ( I I}JiPO I, a conunon £, rtiliz r, is made
from reacting phosphoric acid, II: IP04 , with mnmonia.
a. Write the equation for thi reaction.
b. If 10.00 g of ammonia react, how many m' 1 s of fertilizer will be produ .ed?
c. What mass of anmlOnia will react v,rith 2800 l<g of H~iPO-l?
6. The following reaction shows Ule ynLhe i . of zinc citrate, a ingredient in
toothpaste from zinc car onal \ and citric acid.
3ZnCO;J( oS)
+2
a. How many mol
(iH ,07(aq) --') Zn:l( Ctjl-l:)07)~(oq)
+ : H~O(l) +
3C02 (g)
of ZnCO:1 and C6 H s0 7 are required to produce 30.0 mol of
Zn3 (C6 f!5()7)2'
b. What quantities in kilograms, of H20 and C()z are produced by th r act ion
of 500. mol of 'itlic a 'icl?
7. M thyl butanoate, an oily substance with a sLrong fruity fragrance, can be
made by reacting butanoic acid with methanol according to the following
equation:
C;3II7coon
+ CH;3()f! --') C:3 H7CO CH:3 + HzO
a. What mass of m thyl butanoate is produced [rom the reaction of 52.~ g of
butanoic acid?
b. In order to pmify melhyl bUlanoat , wat r mu be removed. What mass of
water is produ' d from the reaction of 5800. g of methanol?
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Holt ChemFile: Problem-Solving Workbook
108
Stoichiometry
ame
_
lass
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Date
_
I Problem Solving continued
8. Ammonium nitrate decomposes to yield nitrogen gas, water, and oxyger gas
in the following reaction:
2 H-!NO.. ---7 2 ~ + O2 + 4H2 0
a. How many moles of nitrogen gas are produced when 36.0 g of NH4 N03
reacts'.
b. If 7.35 mol of H2 0 are produ 'ed in this reaction, what mass of NH"IN03
reacted?
9. Lead(ll) nitrate reacts with potassium iodide to produce I adell) iodide and
potassium nitrate. If 1.23 mg of lead nitrate are consumed, what is the mass of
th potassium nitrate produced?
10. A car battery produces electrical energy with th following chemical reaction:
PbCs) + Pb0 2 (s) + 2H2 80 4 Caq) ---72Pb80 1(
)
+ 2H2 0(l)
If til battery los s 0.34 kg of lead in this reaction, how many moles of leadCm
sulfate are produced?
11. In a space shuttle, the ~02 that the crew xhalcs is r moved from th air by a
reaction within canisters of lithium hydroxide. On average, each astronaut
exhales about 20.0 mol of CO2 daily. What mass of water will be produced
when this amOLmt reacts with LiOH? The other product of the reaction is
Li2 C03 •
12. Water is sometimes removed from lhe products of a reaction by placing them
in a clo eel container wi h excess P40 La' Wat r is absorbed by the following
r action:
P.10 1O + GIIzO ---7 4H;1P0I1
a. What mass of water can be absorbed by 1.00 x 102 g of P40 LO?
b.lf the P40JO in the container absorbs 0.614 mol oJ water, what mass of
H3 P0 4 is produc d?
c. If the mass of the container of P 4010 increases from 56.64
(J
to 63.70 g, how
many moles of water are absorbed.
13. Ethanol, C2 Hs OH, is considered a clean fuel because it burns in oxygen to
produce carbon dioxide llilel wat r with few trace pollutants. If 95.0 g of H 20
af produc d during the combustion of ethanol, how many grams of ethanol
were present at th beginning of the ration?
14. Sulfw- dioxide is one of the major contlibutors to acid rain. Sulfur dioxide can
react with oxygen and water in the atmosphere to fonn ulfuric acid, as
shown in the following equation:
2H~O(l)
+ O2 (0) + 280 2 (g) ---72H z80 4 (aq)
If 50.0 g of sulfur dioxide from pollutants reacts with water and oxygen found
in the air, how many grams of sulfUlic acid can be produced'? How many
grams of oxygen are used in the process?
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Holt ChemFile: Problem-Solving Workbook
109
Stoichiometry
r-
I Problem Solving continued
15. When heated, odium bicarbonate, NaHC03 , d
omposes into sodium .arbon­
al, azCOs , wat r, and carbon dioxide. If 5.00 g of aHC0 3 decompo e ,
what is the mass of the carbon dioxide produc d?
16. A reaction betw
n hydrazine, zH4 , and dinltrogen tetroxide, NZ0 4 , has
b n used to launch rockets into space. The r aclion produces nitrogen gas
and water vapor.
a. Write a balan' d hemical equation for this reaction.
b. What is the mole ratio of N Z0 4 to 2 ?
c. How many moles of N2 will be produc d if 20 000 mol of N zH4 ar used by
a rocket?
d. How many gram of H 2 0 are made wh n 450. kg of N Z0 4 ar consumed?
17. Joseph Priestley is credit d with the discovery of oxygen. He produced O2 by
heating mercury(ll) oxid ,HgO, to decompose it into its elements. How many
moles of oxyg n could Priestley have produced if he had decomposed 517.84
g of mercury oxide?
18. Iron(Ill) chloride, Feels, can b mad by the reaction of iron with chlorine
gas. How mu ,11 iron, in grams, will be ne ded to completely react with 58.0 g
of Clz?
19. Sodium ulfide and cadmium nitrate undergo a daub] -eli placement reaction,
as shown by th following equation:
• a.l + Cd(NO:~)z -t 2 aNO· + CdS
What is the mass, in milligrams, of cadmium ulfide that can b made from
5.00 mg of sodilml sulfide?
20. Potassium p rmanganate and glycerin react e"h'])losively according to the
following equation:
14KMn04 + 4C3H·;(OH}I -t 7K2 COS + 7MnZ03 + 5C02 + 16HzO
a. How many moles of carbon dioxide can be produced from 4.44 mol of
KMn° I ?
b. IT 5.21 g of H2 0 are produced, how many moles of glycerin, CsH5 (OH)3,
w re used?
c. If 3.39 mol of potassium carbonate are made, how many granlS of man­
ganese(ill) oxide are also made?
d. How many grams of glyc rin will be needed to react with 50.0 g of KMn 4?
How many grams of CO2 will be produc d in the same ration',
21. Cal ium carbonate founel in lim sLone and marbl rats with hydrochlOlic
acid to fonn calcium chloride, carbon dioxide, and water accordulg to the
following equaUon:
aCO;JC .) + 2HCI(aq) -t CaClz(flq) + COz(g) + HzO(l)
a. What mass of HCI will be needed to product" 5.00 x lOa kg of CaCh?
b. What mass of CO 2 could be produced from the reaction of 750 g of CaC03 ?
Copyright
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Holt ChemFile: Problem-Solving Workbook
110
Stoichiometry
Name
_ Class
_
Date
_
I Problem Solving continued
22. TIle fu I used to power the booster ro kets on the space shuttl is a mixture of
aluminum metal and ammonium perchJorat . The following balanced quation
represents the r action of these two ingredient.s:
3Al(s) + 3NH4 CI04 (s)
---7
Al 2 0;J(s) + AlCI3 (g) + 3 O(g) + 6H 2 0(g)
5
a. If 1.50 x 10 g of Al rat, what mass of NH4 CI04 , in grams, is required?
b.lf aluminum r acts with 620 kg of NH 4 CI04 , what mass of nitrog ,n monox­
ide is produc d?
23. Pho photic acid is typically produ ed by the action of sulfuric acid on rock
that has a high content of calcium phosphate according to the follOWing
equation:
3H 2S04 + Ca3(PO,1)2 + 6H~O
[caS0 4 ·2H 2 0] + 2H sP01
a. If 2.50 x 10 kg of H2 S04 react how many moles of HSP04 can be made?
---7
5
b. What mass of calcium sulfate dihydrate is produc d by the reaction of 400.
kg of cal ium phosphate?
c. If the rock being used contains 78.8% Ca3(P04)2, how many metric tons of
H3 P04 can be produced from 68 metric tons of rock?
24. Rusting of iron occurs in the pre nce of moisture according to the following
equation:
4F (s) + 302 (g) ---7 2Fe203( s)
Suppose that 3.19% of a heap of steel s rap with a mass of 1650 kg rusts in a
year. What mass will the heap have after one year of rusting?
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Holt ChemFile: Problem-Solving Workbook
111
Stoichiometry
b. CSH 16 0 4
c. C4 H 6 0 4
d. ClzH1206
6. a. C4 H4 0 4
b. C4H Oz
c. C9H 1Z OS
7. KZS2 5, polassium metabisulfite
8. PbSO_1
9. CrZSSOlZ or CrZ(S04)3, chromium(TII)
sulfate
10. C9 H6 0 1
11. C 5Hg ~lJ the empirical formula and the
mole Will" formula are the same
12. Th molecular fomlUlas [the
compOlmds are different multiples of
the same empirical formula. (FYI: The
first could be acetic acid, CZH 4 0 Z , and
the second could be glucose, C6 H [zOG,
or some other simple sugar.)
16. a. 2 ~H4 + 204 ~ 3Nz + 4HzO
b. 1 mol NZ0 4 to 3 mol z
c. 30000 mol N z
d. 3.52 X 10" g H20
17. 2HgO(s) ~ 2Hg(l) + Oz(g); 1.1954 rna]
Oz
18. 2Fe + 3Cl z ~ 2FeCl 3 ; 0.5 g F
19. 9.26 mg CdS
20. a. 1.';9 rna] ,Oz
b. 0.0723 mol CSH5 (OH)s
c. 535 g Mnz0:;l
d. 8.33 g 3H,,(OHh 4.97 g COz
21. a. 3.29 X lOs kg of Hel
b. 330 g CO z (s)
22. a. 6.53 X 105 g NH 4 CI04
b. 160 kg NOCg)
23. a. 1.70 x 106 mol HS P0 4
b. 666 kg of aS0 4 ·2HzO
c. 34 m~tric tons of HS P04
24. 1670 kg
Stoichiometry
LIMITING REACTANTS
5. a. C6 H12SS
STOICH 10METRY
1. 15.0 mol (NH4)2S04
2. a. 51 g AI
b. 101 g Fe
c. 1.83 mol FezOo
3. 0.30 g Hz
4. H zS04 + 2KOH ~ K z 1 + 2HzO; 1.11
g H 2 S04
5. a. H::JP04 + 2NH::J ~ (
zHP04
b. 0.293 mol (NB,,)zHP0 4
c. 970 kg NH3
6. a. 90.0 mol Zncos ; 60.0 mol C6 Hs 0 7
b. 13.5 kg H2 0; 33.0 kg CO 2
7. a. 60.9 g methyl butanoate
b., 2G1 g HzO
8. a. 0.450 mol z
b. 294 g NH 1N0 3
9. PbCNOs)z + 2Kl ~ Pp1z + 2KN03 ;
0.751 mg RNO;j
10. 3.3 mol PbS0 4
11. 2LiOH + CO 2 ~ HzO + Liz Os; 60 g
lIz
12. a. 38.1 g H2 0
b. 40.1 g H1 P0 4
c. 0.392 mol II z0
13. C~JI"OH + 30z ~ 2COz + 3HzO; 81.0
g zH 5 0H
14. 76. g H zS04 ; 12.5 g Oz
15. 2 aRGOo ~ Na,z Os + H2 0 + CO z ;
1.31 g COz
°
Ra
1. 2ZnS + 302 ~ 2Zn + 2S0 z; ZnS is
limiting
2. a. AI is llmi .ing
b. 4.25 X 10- 3 mol AI 20 a
c. Oz is limiting
3. a. CuS is limiting
b.1 .6 g CuO
4. Fe is limiting; 0.158 mol u
5. 54 g Ba( O.)z
6. a. 38 g Brz
b. 510 g 12
7. a. Ni is in excess
b. 0.2 g i( 03)Z
8. CS 2 (g) + 30 z(g) ~ 2S04 (g) + CO 2 (g)
0.80 m 102 re ain
9. a. 0.84 g Hg(NHz)Cl
b. 0.84 g
10. a. 2Al(s) + 2 aOH(aq) + 2H 2 0(l)
~ 2NaAl0 z(aq) + 3H2 Cg)
b. NaOH is limiting; 0.56 mol lIz
c.. AI should be limiting because you
would not want alwninum metal
remaining in the drain.
11. a. 0.0422 mol Cn; 0.169 mol RNO.3
b. I is in excess
c.3. 2 g HzO
12. a. 2.90 mol NO;
4. 5 mol 1-lzO
b. H3 is limiting
c.. H~~ is limiting; 1.53 X 10:3 kg NO
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Holt Chemistry
326
Answer Key