NAME __________________________________
NOTES: UNIT 6 (3): REDOX:
WRITING FORMULAE: INORGANICS
I-IV) Oxidation Numbers through Inorganic Nomenclature
V) Given The Name...Write The Empirical Formulae: This section is about going from a nomenclature (the name)
to an empirical formula …and there’s no stoichiometry 
A) Review: Empirical Formula: The chemical formula of a substance representing the * simplest
mole (molar) ratio between the elements (that is… the subscript ratio)
Let’s get a few things out in the open...
1) You need to know your polyatomic ions (Table E).
2) You need to analyze consistently / constantly. You must actively interpret.
3) Please note that inorganic compounds are often categorized by the anion (that is,
they are often categorized by the more electronegative species)
e.g) oxides = binary ionic or molecular compounds w/ Oxygen
in the -2 oxidation state.
e.g. Fe2O3, ZnO, SO3, Al2O3, UO3, SiO2, NO, N2O3
halides = binary ionic or molecular compounds of Grp 17 elements
in the -1 oxidation state
e.g. CaI2, NaF, AgCl, AlBr3, NH4Cl
phosphates = compounds with the polyatomic ion (PO4)3e.g. Na3PO4, (NH4)3PO4, AlPO4
hydroxides= inorganic compounds w/ the polyatomic ion (OH)1e.g. NaOH, Ca(OH)2, Fe(OH)3 ...operationally, metal
Formula
Name
Formula
Name
H3O1+
hydronium
CrO42-
chromate
dimercury I
2-
dichromate
1-
Hg2
2+
1+
NH4
C2H3O21CN
12-
Cr2O7
ammonium
MnO4
permaganate
acetate
NO21-
nitrite
cyanide
1-
nitrate
NO3
2-
CO3
carbonate
O2
peroxide
HCO31-
hydrogen
carbonate
OH1-
hydroxide
(bicarbonate)
C2O42-
oxalate
PO43-
phosphate
ClO1-
hypochlorite
SCN1-
thiocyanate
chlorite
SO32-
sulfite
chlorate
SO42-
sulfate
perchlorate
HSO41-
hydrogen
sulfate
S2O32-
thiosulfate
ClO2
1-
ClO3
1-
ClO41-
hydroxides are classified as Arrhenius bases, when
dissolved in water.
417
A) Here’s the challenge:
How can you get the correct subscripts for a compound’s formula? ...
1) Answer: For Molecules: * Turn the prefixes of the name into the subscripts.
prefix
value
mono
1
di
2
tri
3
USE THE PREFIXES as your guide, there’s no need to play around with the oxidation
states. Note that with the exception of the diatomic elements, the inorganic molecules
about which we are learning are binary inorganic molecular compounds (and thus have
a name ending in –ide). Essentially, for our course, ternary molecular compounds are
organic compounds and are named according to the rules from Unit 3. Recall a prefix
indicates a molecular species, in our class.
tetra
4
Practice:
When
no prefix is used, you may assume a subscript of “1”.
penta
5
hexa
6
hepta
7
octa
8
carbon dioxide * CO2
dinitrogen pentoxide * N2O5
sulfur trioxide * SO3
nitrogen trichloride * NCl3
carbon monoxide * CO
dinitrogen monoxide * N2O
dichlorine heptoxide * Cl2O7
carbon tetrachloride * CCl4
a) N.B. When asked to write the formula of any of the diatomic elements, always
record the elements symbol with a subscript of 2.
H
17
7N
O
F
Cl
e.g) hydrogen gas or dihydrogen *H2
oxygen gas or dioxygen *O2
Br
I
i) In some texts you might actually read the names of the diatomic elements such as
N2(g) as dinitrogen, or pure O2(g) as dioxygen. You’ll note that I have named diatomic
elements like H2(g) , as dihydrogen, as well as hydrogen gas, just to get you in the
interpretive habit. It is a pretty new trend, especially in Europe, but you’re the next
generation of scientists, so I want you exposed to it. But know this, when a
questions uses the name “hydrogen” it may / may not mean H. But, when the
name hydrogen gas is used, it is assuredly referring to H2(g), the diatomic
element.
418
2) Writing the formula for (Inorganic) Ionic Compounds, uses different rules than those
used for writing the formula for inorganic molecular substances.
a) Review: With few exceptions, for most inorganic compounds, the symbol of the
lower electronegative element is written * first in the formula
it’s the one with the * positive
(so
oxidation number. The second element is,
the element with the greater electronegativity value or the species with the
* negative
oxidation number.
3) Process: Use oxidation states and subscripts to write a formula in which all state add to 0
4) Process: The Crisscross Method.
Concept: The absolute values of the oxidation numbers become the subscripts for
the opposite species. These are then reduced to the simplest whole-number
ratio (the empirical formula).  Ionic compounds are written in their
empirical formula!!!!
a) Assign the oxidation state associated with each cation & anion species
b) Make that oxidation state of the first species into the subscript of the second species
etc. Reduce the subscripts to the simplest whole number ratio.
Note1 Instead of crisscrossing, you may arithmetically determine the relationship.
Note2 The sum of the positive charge and the sum of the negative charges MUST add up to zero.
Note3 You MAY NOT adjust the charges of the cations or anions to get a total charge of zero.
Note4 You MAY adjust the subscripts to get a total charge of zero.
3) e.g.) sodium sulfide
Na+1 S-2
calcium nitrate
Ca+2 (NO3)-1 = Ca(NO3)2
You will note that the subscript for nitrate is written outside a set of
parentheses. It is UNACCEPTABLE to write CaN2O6
419
potassium chloride
calcium sulfate
aluminum oxide
aluminum phosphate
aluminum chloride
zinc carbonate
magnesium phosphate
calcium fluoride
4) Writing the formula by interpreting Stock’s system
this roman numeral tells you the  oxidation # to use
titanium (IV) oxide
this roman numeral identifies
the positive oxid. # to use
chromium (III) oxide
Ti+4 O-2
manganese (VI) sulfide
iron (III) oxide
Mn+6 S-2
Be sure to use iron
in the +2 state
iron (II) oxide
nickel (III) carbonate
copper (II) sulfate
gold (III) thiosulfate
Answers: KCl, Al2O3, AlCl3, Mg3(PO4)2, CaSO4, AlPO4, ZnCO3, CaF2 …. TiO2, MnS3, FeO, CuSO4, Cr2O3, Fe2O3 Ni2(CO3)3 Au2(S2O3)3
420
Given a written name and asked for the chemical formula of a compound...
Confirm it is a molecule, made
from nonmetal atoms
Confirm the first element name
represents a metal, telling you that the
compound is an ionic compound
 correctly interpret the elements’
names and write down the correct
symbols
 correctly interpret each (or any)
prefix and convert it into a
subscript for the nonmetal species
to which the prefix applies
 correctly interpret the elements’
names and write down the correct
symbols
or
When the name has
a roman numeral be
sure to...
 correctly interpret the
roman numeral & assign it
to the METAL species, as
an oxidation state (it is not a
When there is no
roman numeral be
sure to...
 assign the correct positive
oxidation state to the metal
species, using your grasp of
the Periodic table
subscript)
 correctly assign the negative
Summary:
compounds
ionic
molecular
X+# Y-#
use the
prefixes
 correctly assign the negative
oxidation state to the other
species, using algebra or
your reference charts &/OR
oxidation state to the other
species, using algebra or
your reference charts &/OR
confirm the relationship
between the oxidation states,
either arithmetically or by
the crisscross method, so that
the total sum of the
oxidations states adds up to
be zero
confirm the relationship
between the oxidation states,
either arithmetically or by
the crisscross method, so that
the total sum of the
oxidations states adds up to
be zero
 write the final formula as an
empirical formula
 draw parentheses around any
polyatomic ion, which has an
assigned subscript of 2 or
greater (be especially careful
when dealing with (OH)1and (CN)1-
 erase all oxidation states
from your final answer.
There should be no charge
 write the final formula as an
empirical formula
 draw parentheses around any
polyatomic ion, which has an
assigned subscript of 2 or
greater (be especially careful
when dealing with (OH)1and (CN)1-
 erase all oxidation states
from your final answer.
There should be no charge
421
DIRECTIONS: Write the empirical formula for each compound, using either method from the previous pages.
Remember for the arithmetic method:


Be sure you have written the appropriate symbol for each species
Assign the oxidation numbers and multiply them by whole-number subscripts that have their total add u to 0.
Remember for the crisscross method:
•
Read the name of each given compound and re-write the compound using the elements’ symbols.
•
Assign oxidation #’s to each cation and each anion (you can assign any PAI its overall charge)
•
“Crisscross” the oxidation numbers, ignoring the charges, thus making the oxidation numbers into subscripts
•
Reduce to the simplest whole-number ratio (the empirical formula)
•
N.B. DO NOT carry over the + and - signs when making subscripts
When the subscript is 1 it is not written (CaCl2 NOT Ca1Cl2)
When one of the ions is a PAI and its subscript is 2 or more, enclose it with ( )
Compound Name
1.
2.
titanium (II) oxide
(binary or ternary ?)
vanadium (IV) oxide
Symbols and Ox. #’s
Ti2+
O2-
+4
-2
V
O
(binary or ternary ?)
3.
copper (II) nitrate
Cu+2
(NO3)-1
Crisscross For Subscripts
Ti2O2
simplify to empirical formula
Empirical Formula
TiO
Make those oxidation states into
subscripts, using absolute values!!
V2O4
Cu1(NO3)2
Cu(NO3)2
(binary or ternary ?)
4.
cadmium oxide
(binary or ternary ?)
calcium hydroxide
5.
6.
(binary or ternary ?)
nickel (III) phosphate
(binary or ternary ?)
barium phosphate
7.
(binary or ternary ?)
gold (I) thiosulfate
8.
(binary or ternary ?)
chromium (II) sulfate
9.
(binary or ternary ?)
manganese (VI) oxide
10
(binary or ternary ?)
manganese (IV) oxide
11
(binary or ternary ?)
12 mercury (I) chloride
13 nickle (III) oxide
422
Symbols and Ox. #’s
Compound Name
Crisscross For Subscripts
Empirical Formula
14 potassium dichromate
15 silver nitrate
16 vanadium (V) oxide
17 lithium hydroxide
18 aluminum phosphate
19 tin (II) fluoride
20 chromium (III) sulfate
21 zinc chloride
22 sodium hypochlorite
Selected Answers:
2) VO2
3) Cu(NO3)2
10) MnO3
11) MnO2
18) AlPO4
19) SnF2
4) CdO
12) HgCl
5) Ca(OH)2
13) Ni2O3
20) Cr2(SO4)3
6) NiPO4
14) K2Cr2O7
21) ZnCl2
7) Ba3(PO4)2
15) AgNO3
8) Au2S2O3
16) V2O5
9) CrSO4
17) LiOH
22) NaClO
423
HOMEWORK : WRITING FORMULAE For questions 1-10 please re-write each equation and THEN
balance it by inspection . I have “filled-in” some of the blanks for you. The answers are on the next page. HINT: Don’t forget the
7-Club members have the general formula of “X2”. Note: if asked to write the formula for something like “oxygen” you are being
asked to write the formula for oxygen gas (O2). They are the same thing, effectively and are used interchangeably. Or, when you are
asked to write the formula for sodium, it is sodium metal, the pure element, you are asked to write.
compounds
1)
+ nickel (II) chloride  aluminum chloride
aluminum
Al
2) gold (III) sulfide + dihydrogen gas

3) silver sulfide
+ dioxygen gas

____________
copper

O2
+ silver nitrate
Cu
5) sodium
+
+
_________
+
_________
+
H2O
Au
+
+
+
_____________
copper (II) nitrate

+
NaOH
+

use the
prefixes
+
_____________
silver
+
Ag
+
dihydrogen
+
sodium phosphate


X+# Y-#
silver oxide
__________________

molecular
_______________
sodium hydroxide

ionic
dihydrogen sulfide
_______________
aluminum thiosulfate
+
+
sulfur dioxide
+ sodium hydroxide
_________________
______________
gold

water
6) iron (II) phosphate
7) barium bromide

nickel
_______________ +

H2____
_____________
4)

+ _____________
+
barium thiosulfate
H2
+
iron(II) hydroxide
+
_______________
+
aluminum bromide
_____________ +
________________
424
+ potassium phosphate 
8) lead (II) nitrate
_____________
9) nitrogen gas
+
or: dinitrogen
________
+
oxygen
K3PO4


+
___________________ +
potassium nitrate
_______________
nitrogen dioxide
or dioxygen
+ ________ 
lead (II) phosphate
nitrogen dioxide
___________________
Ans For 1-9 of the Homework
3 NiCl2(aq) 2 AlCl3(aq) + 3 Ni(s)
1)
2 Al(s) +
2)
Au2S3(s) + 3 H2(g)  3 H2S(g) + 2 Au(s)
3)
2 Ag2S(s) + 3 O2(g)  2 SO2(g) + 2 Ag2O(s)
4)
Cu(s) + 2 AgNO3(aq)  Cu(NO3)2(aq) + 2 Ag(s)
5)
2 Na(s) + 2 H2O(l)  H2(g) + 2 NaOH(aq)
6)
Fe3(PO4)2(aq)
7)
3BaBr2(aq) + Al2(S2O3)3(aq)
8)
3Pb(NO3)2(aq)
9)
N2
+ 6 NaOH(aq)  2 Na3PO4(aq)
+ 2K3PO4(aq)
 3BaS2O3(s)
+
3 Fe(OH)2(s)
+ 2AlBr3(aq)
 Pb3(PO4)2(s) + 6KNO3(aq)
+ 2 O2  2 NO2
For questions 10 – 15 re-write each equation . Once that task is completed, answer the remaining questions.
It’s good to review!!!
10) Write the reaction equation of aluminum metal and oxygen gas to produce the compound aluminum
oxide. (recall; oxygen is a diatomic element)
______________________________________________________________________________________________________________________
a) When balanced using the simplest whole-number ratio, what is the coefficient of oxygen gas?
b) What is the reducing agent in the above reaction? ______________
c)
Is aluminum oxide an ionic compound or molecular compound?_________________
Based on your answer, what type of bond is found in aluminum oxide? _______________
d) Calculate the number of moles of aluminum required to produce 7.43 moles of aluminum oxide
in an excess of oxygen.
425
11)
nitrogen gas
dinitrogen
+

oxygen gas
dioxygen
__________ + __________
dinitrogen tetroxide + 98.3 kJ
dinitrogen tetroxide

__________________ + 98.3 kJ
a) What is the oxidizing agent in the above reaction? ______________
b) Is the reaction exothermic or endothermic? _______________
c) Calculate the grams of dinitrogen tetroxide produced when 87.00 grams of oxygen gas are consumed
in an excess of nitrogen gas.
d) With how many significant figures should you record your answer to 11c)? _____________
12) a) Write the formula for each substance in the reaction equation :
Lead (II) oxide
+ sulfur dioxide
 lead (II) sulfide + oxygen gas
________________________________________________________________________________________
b) When balanced using simplest whole number ratios, what is the molar ratio between
lead (II) oxide and oxygen?
c) Is sulfur dioxide an ionic compound or a molecular compound?
_________________________
Based upon your answer, what type of bonding is found in sulfur dioxide? ___________________
d) Calculate the moles of lead (II) oxide required to produce 4.55 mol of oxygen, in an excess of
sulfur dioxide.
426
13) Uranium and fluorine gas (or: difluorine gas) can be reacted to produce uranium hexafluoride, which actually
has covalent bonds (and thus a molecular compound).
a) Using whole number coefficients and correct formulae, write the balanced chemical reaction for the
production of uranium hexafluoride from uranium and difluorine.
______________________________________________________________________________
b) To what does the prefix “hexa” of the name uranium hexafluoride refer? __________________
____________________________________________________________________________
c) What is the reducing agent in the above reaction? ________________
d) Calculate the grams equivalent to 1.27 mol of uranium hexafluoride (M = 352 grams).
e) With how many significant figures should your answer to 13 d) be recorded? _______
f) Does the above reaction have a “spectator ion”? ____________
g) What is the family name to which fluorine belongs on the Periodic Table? ________________
14) There is a group of compounds called: metal carbonates. They are made of metal cations and the carbonate
polyatomic ion. An example would be CdCO3. As a rule of thumb, when a metal carbonate compound
compound is heated, a metal carbonated thermally decomposes (breaks down) into metal oxide and carbon
dioxide gas. Thus, heating cadmium carbonate (CdCO3) causes the decomposition into cadmium oxide
and carbon dioxide gas.
a) Write the balanced reaction equation of cadmium carbonate as it produces cadmium oxide and
carbon dioxide gas.
________________________________________________________________________________
b) Is the above reaction a redox reaction? __________________Defend your thinking ________
________________________________________________________________________________
________________________________________________________________________________
c) Based upon the reading, name the products of the thermal decomposition of calcium carbonate.
The products are: _________________________ and ________________________
427
15) When I was a kid (as the Earth cooled), disappearing ink was all the rage. I could order it from a supply
store, using an address found at the back of any favorite comic book.
In essence, disappearing ink is an inky-blue colored aqueous solution which can be squirted onto
clothes … making a giant “ink” stain. Yet, after a few moments of panic (all on the part of the
victim), the ink stain, magically disappears with no harm to the clothing. Imagine my joy
when I learned how to make it myself !!!
The trick is in two parts. First, a non-redox reaction occurs, in which a solution of low molarity
sodium hydroxide is converted into harmless washing soda, [a weak detergent] with exposure to an
acidified form of carbon dioxide from the air [carbon dioxide + water produces carbonic acid].
So the reactants are sodium hydroxide and carbon dioxide gas. These react to produce
sodium carbonate (washing soda) and water.
The second piece to the puzzle is an acid/base indicator. Thymolphthalein [thī-mōl-thā-lēn] is a
deep midnight blue, when exposed to a strong base, like sodium hydroxide. As sodium carbonate
[a weak base] is produced, (and the sodium hydroxide is consumed) the pH of the system drops.
This means that the thymolphthalein is no longer in the presence of a “strong base” and the
indicator becomes colorless as the reaction proceeds. Thus, the blue color (the fake ink)
“disappears” over time, all due to the change in pH and the indicator’s change in color!
a) Write the balanced chemical reaction between sodium hydroxide and carbon dioxide, which produces
sodium carbonate and water. (Don’t worry about the thymolphthalein . It plays no role in the production of the products … it
simply changes color in reference to the change in the level of pH [acidity])
__________________________________________________________________________________
b) The passage claims that this is a “non-redox” reaction. Why is that statement correct?
___________________________________________________________________________________
___________________________________________________________________________________
c) Calculate the oxidation number of carbon in sodium carbonate. __________
d) Calculate the grams of sodium hydroxide required to make 30.0 mL of a 0.100 M solution.
428
Answers:
10) 4 Al + 3 O2
→ 2 Al2O3
a) coefficient of oxygen gas: 3
b) reducing agent: Al0
c) aluminum oxide: IONIC COMPOUND
type of bond: IONIC BOND
d)
11)
moles of Al = 7.43 mol Al2O3|
4 mol O2
2 mol Al2O3
| =
14.9 mol Al (3 sig figs due to 3 sig figs in the "given")
N2 + 2 O2  N2O4 + 98.3 kJ
a) oxidizing agent: O20 or just O0
b) exothermic
c) grams N2O4 = 87.00 grams O2| 1 mol O2 | 1 mol N2O4 | 92 grams = 125.1 grams O2
32 grams O2 2 mol O2
1 mol N2O4
d) significant figures: 4
(4 sig figs due to 4 sig figs in the "given")
12) 2 PbO + 2 SO2  2 PbS + 3 O2
b) ratio 2:3
c) sulfur dioxide: MOLECULAR COMPOUND
bonding : COVALENT or POLAR COVALENT
d) moles PbO = 4.55 mol O2|
13)
U + 3 F2  UF6
2 mol PbO
3 mol O2
| = 3.03 mol PbO
(3 sig figs due to 3 sig figs in the "given")
b) the number of fluorine atoms per one uranium
c) reducing agent: U0
d) grams UF6 = 1.270 mol UF6 | 352 grams | = 447.0 grams UF6
1 mol
e) significant figures 3
(4 sig figs due to 3 sig figs in the "given")
f) spectator ion: NO
g) family: HALOGENS
14) CdCO3  CdO + CO2
b) NO: THERE ARE NO CHANGES IN THE OXIDATION STATES OF THE REACTANTS.
c) CaO and CO2
15) 2 NaOH + CO2  Na2CO3 + H2O
b) THERE ARE NO CHANGES IN OXIDATION STATES OF THE REACTANTS.
c) carbon is +4
d) M = moles/Liters
then:
OR
0.100 = x/0.030
x = 0.0030 moles NaOH
grams NaOH = 0.0030 moles NaOH | 40 grams | = 0.12 grams NaOH (2 sig figs due to 2 sig figs in the "given")
1 mol NaOH
429
NAME ____________________________
A LITTLE INTEGRATED REDOX CHEMISTRY
DIRECTIONS: There are few surprises. Most of this work is found in Unit 7: Redox and of course, there is
some stoichiometry. Use your notes, your Reference Charts and your smarts to complete each problem.
1)
aluminum
+
nickel (II) chloride

aluminum chloride + nickel
__________ + _______________  _______________
+ _______________
a) Write the formula for each substance in the above chemical reaction.
b) Balance the chemical reaction, using coefficients in the simplest whole number ratio
c) Is the reaction a redox reaction? __________ Defend your reasoning using
chemical theory/reasoning (not tricks…) from the unit of study.
__________________________________________________________________
___________________________________________________________________
d) If and only if, it were a redox reaction, what would be the oxidizing agent? ___________
e) Calculate the grams of nickel produced when 122 grams of aluminum are consumed in
an excess of nickel (II) chloride.
2) Write the formula for phosphorus pentachloride _____________
-1
____3) What is the oxidation number of manganese in the polyatomic ion (MnO4) ?
____4) An element can make the following compounds with oxygen: XO and XO2 . Which of the
following elements might be “X”?
a) potassium
b) titanium
c) silver
d) zinc
____5) What is the empirical formula for C6H12
a)
C6H12
b) CH
c) C2H
d) CH2
430
6) aluminum carbonate + calcium hydroxide  aluminum hydroxide + calcium carbonate
_____________
+ ___________
 ____________
+ ______________
a) Write the formula for each substance in the above chemical reaction.
b) Balance the chemical reaction, using coefficients in the simplest whole number ratio
c) Is the reaction a redox reaction? __________ Defend your reasoning using chemical theory
from the unit of study.
__________________________________________________________________
___________________________________________________________________
d) If and only if, it were a redox reaction, what would be the oxidizing agent? ___________
______7) What is the reducing agent in the reaction: 2 PaI5(s)  2 Pa(s) + 5 I2(s)
8) The following represents the chemical production of ozone: 3 O2(g) + 284.3 kJ  2 O3(g)
a) Is the reaction exothermic or endothermic? ___________
b) Is the reaction a redox reaction or a non-redox reaction? ____________
These Challenges are optional:
Challenge1  The mineral crocidolite, is a form of asbestos. It has the formula, Na2Fe5(Si4O11)2(OH)2 .
The mineral has ions of Fe+2and Fe+3. How many of the iron ions must be a +2 and how
many must be a +3? (hint: silicon is typically in the +4 when bonded with oxygen. as judged by oxygen’s greater electronegativity value)
Challenge2  The mineral ultramarine is a beautiful blue pigment used in oil-based paints. It has the ability to
maintain its beauty as it resists oxidation (and thus color change) in bright light. It was more
valuable than gold during the Renaissance!
It was first used in 6th century Afghanistan. Ultramarine comes from the mineral lazurite (found
in lapis lazuli). I have cufflinks made with lapis lazuli. Some of the “blue” component of
ultramarine of lapis is represented here, with the incomplete formula of: Nax[Al6Si6O24]S2,
where the sulfur is present as the disulfide polyatomic ion, (S2)-2. What is the value of “x”?
431