Download Ionic Bonding BasicsII

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Name: ___________________________Unit 5: Ionic Bonding Basics & Formulas
I.What is a bonding?_________________________________________________
__________________________________________________________________
Types of Bonding:
Electrons shared: ____________________________________________________
Electrons transferred: ________________________________________________
II. IONS:
“+ion” __________________________________________ called _______________
called: _____________ # electrons lost = _____________
“-ion” __________________________________________ called _______________
called: _____________ # electrons gained = ___________
III. Why do atoms form bonds? Let’s look at electron configuration again.
Complete the chart below.
For IONS:
When a positive (+) ion forms, cross out the valence electrons of the atom’s
configuration to get the new ion electron configuration.
When a negative (-) ion forms, add electrons equal in to the negative charge to
valence shell of the atom’s configuration to get the new ion electron configuration.
Atom
Electron
Configuration
# of
Valence
electrons
It’s Ion
Ion Electron
Configuration
# of e-1 now
in outermost
PEL
Na
2-8-1
1
Na+1
2-8-1
8
S
2-8-6
6
S-2
2-8-6 8
8
Mg
Ca
F
Cl
What seems to be the magic number, which shows up in the last column of the chart
above? ________________ In which vertical group on the periodic table do all but one
member have this magical number of valence electrons? _______________________
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These elements are very stable and non-reactive. They are called the Noble Gases.
They do not form compounds easily. Having this number of valance electrons is very
stable. Atoms form bonds so that they can have this number of valence electrons and
mimic the electron configuration of the noble gases.
This is called the
_____________________
What Noble Gas does each of elements mimic when it forms an ion?
ex: Na has 11 electrons (EC: 2-8-1), Na+1 has 11 – 1 = 10 electrons so when Na forms
Na+1, its electron configuration (EC: 2-8) looks like Ne (atomic # 10)
S has 16 electrons (EC: 2-8-6), S-2 has 16 +2 = 18 electrons so when S forms S-2,
its electron configuration (EC: 2-8-8) looks like Ar (atomic # 18
Atom Atom’s # of EC of Atom Ion
Ion’s # of
EC of ion
Ion’s EC
electrons
electrons
looks like
Mg
Mg+2
Ca
Ca+2
F
F-1
Cl
Cl-1
When metals form ions, the electron configuration looks like the __________________
noble gas.
When nonmetals form ions, the electron configuration looks like the noble gas at ______
of its row.
(We have not touched the nucleus, so the ions are still the same element that they were,
but with different properties than their neutral atom!!)
IV. Dot Diagrams of Ions:
Metals lose their valance electrons so a metal ion’s “Dot Diagram” is simply the ion’s
symbol & Its charge ONLY- no dots: _____________
Nonmetals gain enough valence electrons to make 8 valence electrons,
so a nonmetal ion’s dot diagram is the symbol with 8 DOTS and its charge: ________
ION
Dot
diagram
ION
Dot
diagram
ION
Dot
diagram
ION
Ca+2
F-1
Al+3
O-2
Li+1
S-2
N-3
Mg+2
Dot
diagram
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V. IONIC BONDING BASICS
When metals and nonmetals react together, the metal gives always its valence
electrons to the nonmetal forming positive ions whose positive charge is equal to the
number of valence electrons lost. The nonmetal becomes a negative ion whose
negative charge is equal to the number of valence electrons it has gained. The
positive ion, called the cation, and the negative ion, called the anion, are then attracted
to each other forming a new compound.
The three steps in forming an ionic bond are:
1) _________________________________________________________
2) _________________________________________________________
3) _________________________________________________________
Neutral
Metal’s
Dot Diagram
Neutral
Nonmetal’s
Dot Diagram
Na
F
Ca
Br
Mg
O
K
S
Al
Cl
Transfer of electrons
from Metal to Nonmetal
Resulting
Dot Diagram
Formula
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The number of each type of ion that will form the new compound will depend on the size
or magnitude of the charges. The charges must add up to zero. For example, if sodium
reacts with chlorine, sodium forms a Na+1 ion and chlorine forms a Cl-1 ion. Only one of
each ion is necessary because the charges add up to zero: (+1) + (-1) =0 and the formula
of the new compound, sodium chloride, is simply NaCl. If sodium reacts with oxygen, it
still forms an ion with a +1 charge but oxygen will form an anion with a -2 charge. The
new compound, sodium oxide, will require 2 Na+1 for every O-2: 2(+1) + (-2) =0 . The
formula for sodium oxide is Na2O. Remember the charges are written as superscripts
(Na+1) and the counters in formulas are written as subscripts (Na2O). Positive ions are
written first and negative ions are written second in a formula. Lazy chemists do not
bother to write 1 as counter in a formula. The element's symbol stands for the 1. Ionic
formulas are always written in lowest terms. This is known as an empirical formula.
These are binary (2 element) ionic compounds.
VI. DETERMINING CHARGES: To determine the charge that an atom has on the
periodic table, simply look at the upper right corner for the oxidation states of the
element. The oxidation state or number is the charge or apparent charge an atom has in
a compound. For nonmetals it is the FIRST (top) oxidation state ONLY. For many
metals, there is only one possibility for the charge. Transition metals and those
metals close to the “crack”, there are more than one charge.
Look up the charges on the following: Remember to write the charges as superscripts!
Sr
O
Ag
Fe
Cl
Fe
Cu
Cu
N
Cs
P
Br
WRITING BINARY FORMULAS
The ions of the elements combine in such a way that the charges have to add up to zero.
The metal or positive ion (cation) is written FIRST and the nonmetal or negative ion
(anion) is written SECOND. The number one, 1, is generally not written in the formula:
ex. NaCl. Only the number in the charge for each ion is criss-crossed down and turned
into subscripts. Always check that the formula is in LOWEST terms.
K+1 O-2
Pb+4 O-2 ->

K
O

K2O1 or K2O
Pb O -> Pb2O4 simplifies to ________
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Ions to be
Bonded
X+1 and Y-1
How to determine formula
X+2 and Y-2
+2 and -2 add up to zero already
X+3 and Y-3
+3 and -3 add up to zero already
X+2 and Y-1
It takes two -1 charges to cancel out the
+2 charge
It takes three -1 charges to cancel out
the +3 charge
It takes two +1 charges to cancel out the
-2 charge
It takes three +1 charges to cancel out
the -3 charge
Common denominator: 2x3=6 it takes
three +2 to make +6 and two -3 to make 6
Common denominator: 2x3=6 it takes two
+3 to make +6 and three -2 to make -6
It takes two -2 charges to cancel out the
+4 charge
X+3 and Y-1
X+1 and Y-2
X+1 and Y-3
X+2 and Y-3
X+3 and Y-2
X+4 and Y-2
Cation
Anion
Formula
+1 and -1 add up to zero already
VII. NAMING
To name ionic compounds, the name of the positive ion is followed by the name of the
negative ion. Group 1 & 2 Metals, Metals with ONE charge LISTED: name of the
metal ONLY
Metal Ion
Ion’s Name
Na+1
Ca+2
Ag+1
Metal Ion
Ion’s Name
Zn+2
Cd+2
Al+3
Transition Metals and Those under the “crack” with MORE THAN 1 CHARGE listed:
name of metal + the Roman numeral EQUAL to the charge on the ion
Metal Ion
+1
Au
Pb+2
Fe+2
Ion’s Name
Metal Ion
+3
Au
Pb+4
Fe+3
Ion’s Name
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For nonmetals, the ending of the nonmetal’s name with the ending changed to IDE.
Nonmetal Ion’s Name
Ion
Nonmetal Ion’s Name
Ion
F-1
Cl-1
Br-1
I-1
N-3
O-2
P-3
S-2
To name ionic compounds, the name of the positive ion is followed by the name of the
negative ion.
Examples:
NaF: sodium fluoride
AlN: aluminum nitride
AgBr: silver bromide
Na3P: sodium phosphide
Li2O lithium oxide
PbCl2 lead (II) chloride
Try your hand at these! Write the formula and name of these compounds
Cation
ex. Mg+2
Anion
Br-1
1.)
Li+1
F-1
2.)
Al+3
Cl-1
3.)
Sr+2
S-2
4.)
K+1
N-3
5.)
Mg+2
P-3
Formula
MgBr2
Name
Magnesium Bromide
Go Backwards: Given the name, determine the elements involved and their charges &
then write the formulas. Look up charges on the PT for the ions.
Name
Cation
Anion
Formula
1.) Sodium Bromide
2.) Calcium Oxide
3.) Zinc Chloride
4.) Beryllium Fluoride
5.) Potassium Iodide
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VIII. DETERMINING CHARGES AND NAMING of TRANSITION ELEMENTS
Transition elements (metals), which are located in the short groups in the center of the
periodic table and some other metals located near the “crack”, can have more than one
charge. Either you will be told which one to use or the charge can be determined from
the formula, which contains the element. To distinguish between the different oxidation
states or charges of these transition metals, a roman numeral equal to the charge on
the ion is used to name the ion. For example, tin comes in two charges, +2 and +4. Sn+2
is called tin (II) and Sn+4 is called tin (IV). The formula of tin (II) oxide is SnO and
the formula of tin (IV) oxide is SnO2. The charge on the tin makes a difference!
AuCl: gold (I) chloride
AuCl3: gold (III) chloride
If Fe2O3 is iron (III) oxide, what would be the formula for iron (II) oxide? _____
ROMAN NUMERALS: +1 ____, +2 ____, +3 _____, +4 ____, +5 _____, +6 ______
Write the formula and name of these compounds with transition metals:
Cation
Anion
Formula
Name
+2
-1
ex. Pb
Cl
PbCl2
lead (II) chloride
1.
Cu+1
O-2
2.
Ni+3
S-2
3.
Fe+2
I-1
4.
Au+1
N-3
5.
Pb+4
O-2
Going Backwards!
First, look up the charges of the elements given on the periodic table, then write the
formula. Remember transition metals with roman numerals tell you what charge to use
for the metal (first element): gold (III) chloride tells you to use Au+3 and NOT Au+1
Name
Cation
Anion
Formula
+2
-1
ex. Iron (II) iodide
Fe
I
BaI2
1.
Copper (I) fluoride
2.
Copper (II) chloride
3.
Gold (III) oxide
4.
Tin (IV) oxide
5.
Lead (II) phosphide
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Naming the Ionic Compounds from JUST the Formula
Determine if it has a metal with more than 1 charge or not (look up the metal on the P.T.)
(transition or under the crack with more than one charge)
- If yes, then look up the nonmetal’s charge and write the formula with each of
the charges.
Ex . FeO
Fe+2
O-2
 FeO
+3
-2
Fe
O
 Fe2O3
- Whichever formula matches, was the charge on the transition metal that was
used. Since the formula with Fe+2 matches, FeO, then Fe+2 was used.
- Use the Roman numeral equal to this charge in the middle of the compound’s
name. Iron (II)
- Change the name of the non-metal to the ending “ide”. Oxide
- Iron (II) Oxide
- If no, then just use the metal’s name and change the name of the non-metal to the
ending “ide”.
Ex.
AgCl
Ag+1 +1 is the only charge so its Silver Chloride
Remember any element in Groups 1 & 2 have ONLY one Charge!! No Roman
Numeral ever!!!
Formula Possible
Anion
Possible
Name
Cation(s)
formula(s)
+2
+3
-2
Ni2O3
Ni , Ni
O
NiO, Ni2O3
Nickel (III) oxide
LiF
PbO2
SnO
Na3P
ZnBr2
Fe2O3
AuI3
CrN
CuO
Ca3N2
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IX. POLYATOMIC IONS (PAI)
A. Reference Table E
Sometimes groups of atoms bond together by sharing electrons to form ions. This is
known as covalent bonding. Here, one of the atoms in the group brings along a charge and
group of atoms is not neutral. These ions are called polyatomic ions, which means “many
atom” ion. Reference table E contains the formula and name of some of these
polyatomic ions. Complete this chart using reference table E.
PAI name
ex. Ammonium
Formula
NH4+1
PAI Formula
ex.
MnO4
-
Name
Permanganate
-2
1.
Nitrate
6.
CO3
2.
Chlorite
7.
C2H3O2
3.
Chromate
8.
SO4
-2
4.
Sulfite
9.
ClO3
-
5.
Phosphate
10.
OH-
-
What type of charge do most of the PAI have? __________________
Most of these PAI end in _________ or _____________
Two important exceptions are the positive ion _________ (ammonium) and the negative
ion _________ (hydroxide).
B. Writing and Naming Compounds with Polyatomic Ions
When forming compounds with these polyatomic ions, the same rules are followed for
other ionic compounds. The formula must be in lowest terms and the charges must add up
to zero. Parenthesis are used around the polyatomic ion when more than one of these
ions is necessary in a formula: (NH4)2O. We want two NH4+ groups and NOT 42 H’s!!!
To name compounds with polyatomic ions, follow the rules above but for the polyatomic
ions, use the name of the polyatomic ion listed on the reference table.
Ex:
(NH4)2O is ammonium oxide; K2CO3 is potassium carbonate.
Compounds with at least one polyatomic ion are called ternary ionic compounds- more than
2 elements. You can recognize that these compounds have a polyatomic ion because there
is more than two capital letters in the formula!!
ternary ionic compounds:
binary ionic compounds:
K2CO3 and NaClO4
K2O and NaCl
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Try your hand at these! Write the formula and name of these compounds: don’t forget
the parenthesis!!
Cation
Anion
Formula
Name
+2
-1
ex. Mg
ClO
Mg(ClO)2
Magnesium hypochlorite
1.
K+1
NO3
-1
2.
Al+3
ClO3
-1
3.
Sr+2
SO4
-2
4.
K+1
NO2
-1
5.
Mg+2
PO4
-3
Going Backwards! Write the formula from the name of the ternary compound.
Polyatomic ions, which have a negative charge generally, end in ITE or ATE. Hydroxide
(OH-), cyanide (CN-), and peroxide (O22-) are the few polyatomic ions, which are
exceptions.
ex.
Name
Beryllium nitrite
1.
Sodium hydroxide
2.
Calcium sulfate
3.
Potassium chromate
4.
Gold (III) carbonate
5.
**Ammonium perchlorate
** contains 2 polyatomic ions
Cation
Be+2
Anion
(NO2)-1
Formula
Be(NO2)2
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X. Stoichiometry of Formulas
Stoichiometry means math relationship, in this case, involving chemical formulas.
A. Smartie Molecule
a) The smartie candy roll represents a molecule. The different colors of the individual
candies represent different elements contain in the smartie molecule. List the colors
contain in your molecule:
__________________________________________________________________
The list of the different colors of the candies represents qualitative data. Qualitative
data tells what elements are present in a formula.
b) Count the number of each individual color present in the smartie molecule and list them
below in “ROYGBIVW” order.
__________________________________________________________________
The list of the number of each different color of the candies in the smartie molecule
represents quantitative data. Quantitative data tells how much of each element is
present in a formula. Both the type and number of each element is told.
c) Identify the following statements as examples of quantitative or qualitative data.
_________________________The compound contains hydrogen and carbon atoms.
_________________________The compound contains 8 hydrogen and 4 carbon atoms.
B. The MOLE
a) Write the formula of your smartie molecule in “ROYGBIV” order using the number of
each color as a subscript (ex. R3O4....) ____________________________________
b) How many total “atoms” are present in ONE smartie molecule? _____________
(Count up the subscripts)
c) Molecules are too small a unit to count in chemistry. We use the unit called the mole
to count in chemistry. One mole of atoms is equal to 6.02 x 1023 atoms; one mole of
molecules is equal to 6.02 x 1023 molecules, etc.
1 mole of smartie molecules = ______________________________ smartie molecules.
2 moles of smartie molecules = 2 x (6.02 x 1023) = 1.20 x 1024. Since counting in moles
(1,2,3 etc) is so much easier than in molecules (multiples of 6.02 x 1023), this is what we
will use.
Since one smartie molecule contains _________________“atoms”, one mole of smartie
molecules will contain the same number of moles of atoms: ______________________.
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d) Counting moles of atoms in a formula
For 1 mole of each of the following compounds, determine the number of moles of each
element is present and the total number of moles of atoms present:
ex.: KBr: 1 mole K & 1 mole Br ; total moles = 2 moles
Li2O: 2 moles Li & 1 mole O ; total moles = 3 moles
When parenthesis are used, multiply the number of each element inside the parenthesis
by number on the outside the parenthesis:
Sr(NO3)2 Sr = 1 mole; N = 2x1= 2 moles; O = 3x2=6 moles
total moles of atoms = 1 mole + 2 moles + 6 moles = 9 moles
Compound
Number of moles of each element
Total moles present
NaCl
CaCl2
K2SO 4
Al (NO 3)3
Mg3(PO4)2
C. How do you measure moles? With a balance!
a. One mole of an element is equal to the atomic mass of that element in grams. This is
called the gram formula mass (GFM). Simply, look up the atomic mass of the element and
place the unit, grams per mole (g/mole), after the number. To make life easier, round off
the atomic mass to the tenths place. Example: chlorine; Cl use 35.5 g/mole. For
carbon (C), look up the atomic mass of C, it is 12.0 amu so 1 mole of C will have a mass of
12.0 g/mole.
Determine the gram formula mass of the elements given (Don’t forget the units):
Element
GFM
Element
H
Fe
Cu
Mg
Br
S
N
O
Ca
Al
GFM
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b. Gram Formula Mass of Compounds
Since one mole of an element is the atomic mass in grams , the GFM of a compound is the
sum of the GFM of the elements of the atoms in the compound.
KBr K = 39.1 g/mole; Br =79.9 g/mole GFM= (39.1 + 79.9.)g/mole = 119.0 g/mole
Li2O Li = 6.9 g/mole; O = 16.0 g/mole Since there are 2 Li, you must multiply
the GFM of Li by 2: GFM = [2(6.9) + 16.0] = 29.8 g/mole
Sr(NO3)2 Sr = 87.6 g/mole; N = 14.0 g/mole; O = 16.0 g/mole Again, you must
multiply individual GFM by the number of each element present.
GFM = [87.6 + 2(14.0) + 6(16.0)] g/mole = 211.6 g/mole.
Remember to show units & work! Units are g/ mole. NO Work NO CREDIT!!!!
1) NaCl
5) Na2SO4
2) NaOH
6) ZnSO4
3) Mg(OH)2
7) Th(NO3)4
4) KNO3
8) CH3Br
C. Special Formulas: Hydrates
Hydrates are ionic compounds that have certain number of moles of water trapped in the
crystal structure of 1 mole of the hydrate. Gypsum drywall used in the construction of
homes is a hydrate of calcium sulfate. The trapped water in the drywall adds to the fire
protection provided by walls constructed of drywall. The formula of gypsum drywall is
CaSO42H2O. This  means it’s a hydrate. It DOES NOT mean to multiply as it does in
math class. Two moles of water are trapped for every one mole of CaSO4. To calculate
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the GFM of the hydrate, the GFM of the ionic compound is added to the number of
moles of water times the GFM of the water.
GFM of CaSO42H2O = GFM of CaSO4
+
2 x GFM of H2O
GFM CaSO42H2O = [40.1 +32.1+ 4(16.0)]g/mole +2 [2(1.0)+16.0] g/mole
= 172.2 g/mole
Since there are 2 moles of water trapped in the CaSO42H2O, the GFM of water is
multiplied by 2.
What is the GFM of CoCl26H2O ?
GFM of CoCl26H2O =
GFM of CoCl2
+ 6 x GFM of H2O
Since the GFM of H2O is 18.0 g/mole, you can substitute that value in rather than
figure it out each time.
GFM of CoCl26H2O = [58.9 + 2(35.5)] g/mole + 6 (18.0g/mole) =237.9 g/mole
Since there are 6 moles of water trapped in the CoCl26H2O, the GFM of water is
multiplied by 6.
Remember to show units & work! NO Work NO CREDIT!!!!
1) CuSO45 H2O
2) Na2CO310 H2O
Gfm of CuSO4
5 x Gfm of H2O
Gfm of Na2CO3
___ x Gfm of H2O
Gfm CuSO4 + (5 x Gfm H2O) = gfm hydrate
Gfm Na2CO3 +(__xGfm H2O) = gfm hydrate
3) MgSO410 H2O
4) BaCl22 H2O
Gfm of MgSO4
__ x Gfm of H2O
Gfm of BaCl2
__ x Gfm of H2O
Gfm MgSO43 +(__xGfm H2O) = gfm hydrate Gfm BaCl2 +(__xGfm H2O) = gfm hydrate
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IV. Mole Calculations: Calculating Moles From Grams
What is the formula on Ref. Table T for mole calculations? ______________________
Step 1: Calculate the GFM of the compound given.
Step 2: Plug the numbers with units in the formula from ref table T. The grams you are
given are always put “on top,” and the GFM on the bottom.
ex: How many moles of H2O are in 9.0 g?
Step 1: gfm of H2O = 2(1.0) +16.0 g/mole = 18.0 g/mole
Step 2: mole of of H2O = 9.0 g/18.0 g/mole = 0.50 moles (2 sig figs needed)
Calculate the number moles of each compound contained in the grams that are given.
Remember to show formula, units & work! NO Work NO CREDIT!!!! (Remember to use the
gfm of the compound you are given!!) Circle answer.
NO WORK, NO CREDIT !! NO credit for just answers!!!
1) 72 grams of H2O
Step 1: GFM:
Step 2: # moles:
2) 29.25 grams NaCl
Step 1: GFM:
Step 2: # moles:
3) 60. grams of NaOH
Step 1: GFM:
Step 2: # moles:
4) 71 grams of Na2SO4
Step 1: GFM:
Step2: # moles:
16
5) 15.75 grams of HNO3
Step 1: GFM:
Step 2: # moles:
V. Calculating Grams from Moles
To calculate the grams from moles, rearrange the formula given for mole calculations by
solving for grams. The TRIANGLE can be
used to help rearrange the formula:
Step 1: Calculate the GFM of the compound given.
Step 2: Plug the numbers with units in the rearranged formula from ref table T. The
units should cancel out leaving only grams.
Hint to remember: You “MOLETIPLY” to get grams. (Groan all you want!)
ex. How many grams of water are in 2.5 moles?
Step 1: gfm of H2O = 2(1.0) +16.0 g/mole = 18.0 g/mole
Step 2: # grams = (2.5 moles)(18.0 g/mole) = 45 g
Remember to show formula, units & work! NO Work NO CREDIT!!!! (Remember to use the
gfm of the compound you are given!!) circle final answer
How many grams are present in the moles of each compound given?
1) 2.00 moles of AlF3
Step 1: GFM:
Step 2: # grams:
2) 10.0 moles of NaCl
Step 1: GFM:
Step 2: # grams:
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3) 2.50 moles of Mg(OH)2
Step 1: GFM:
Step 2: # grams:
4) 0.50 moles of CH3Br
Step 1: GFM:
Step 2: # grams:
5) 4.00 moles of H2SO4
Step 1: GFM:
Step 2: # grams:
VI: Percent Composition:
What is the formula on Ref. Table T for Percent Composition?
Model for % Composition: How much sugar is there in bubble gum????
What type of data do we need? ____________________________________
How can you remove the sugar? ____________________________________
Data:
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A. Percent Composition when data is given in grams.
In lab, the data recorded will be in grams. To determine the percent of an element in a
compound, plug the grams of the “PART” (ELEMENT YOU WANT) over the MASS of the
whole compound.
example: In the analysis of water, 2.00 g of hydrogen was collected from 18.0 g of
water. What is the mass percent of hydrogen in water.
%mass H = (2.00g/18.0g) x 100 = 11.1%
Note: units must be the same in order to cancel out, there are no units to a percent
Remember to show units & work! NO Work NO CREDIT!!!!
1. Carbon monoxide (CO) was analyzed to contain 6.0 g carbon in a 14 g sample of CO.
What is the percent C in the sample?
Math Formula
Numbers & units plugged in
Answer with unit (%)
Unrounded answer
rounded to proper sig figs
2. A 250. g sample of Cu2S contains 50.0 g of S. What are the percent S ?and percent Cu
in the compound?
Math Formula
Numbers & units plugged in
Answer with unit (%)
Unrounded answer
rounded to proper sig figs
How would you get the percent Cu in the compound?
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3. A hydrate was heated to remove the trapped water. If 3.600 g of water was
removed from 10.000 g the hydrate, what is the percent water? (here, water is the part
and the hydrate is the whole)
Math Formula
Numbers & units plugged in
Answer with unit (%)
Unrounded answer
rounded to proper sig figs
4. The usual form of a hydrate question is this:
A 20.0g sample of a hydrate is heated until all the water is driven off. The mass of the
anhydride compound (hydrate without the water) is 15.0 g. What is the % water? First
you need calculate the difference in the two masses to get the grams of water removed,
then proceed as in #3 above.
Math Formula
Numbers & units plugged in
Unrounded answer
Answer with unit (%)
rounded to proper sig figs
5. Calculate your % sugar (on page 18) when the “taste” is gone from the gum.
Math Formula
Numbers & units plugged in
Answer with unit (%)
Unrounded answer
rounded to proper sig figs
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How is calculating the % sugar in bubble gum similar to the percent water in a hydrate
calculation?
__________________________________________________________________
B. Percent Composition when data is a formula.
Here you use the GFM of the compound for the whole and the GFM of the element
times its subscript for the part.
What is the % of H and C in CH4?
GFM of CH4 = [12.0 + 4(1.0)]g/mole = 16.0 g/mole
GFM of H = 4(1.0) g/mole = 4.0 g/mole (remember there are 4 H)
%mass H = (4.0g/mole/16.0 g/mole) x 100 = 25%
To get % C you repeat the step above
% C = (12.0 g/mole/16.0 g/mole) x 100 = 75.0%
or subtract 25% from 100%.
Note: Because of rounding off, it is not unusual for the sum of the individual percents to
range from 99% to 101%.
Remember to show units & work! NO Work NO CREDIT!!!!
Calculate the percent of each element
1) WO3
GFM:
%W=
%O=
2)
MgCl2
GFM:
% Mg =
% Cl =
21
3)
Na2CO3
GFM:
% Na =
%C=
%O=
4)
KClO3
GFM:
%K=
% Cl =
%O=
5)
Mg(NO3)2
GFM:
% Mg =
%N=
%O=
C. Percent Water in a Hydrate (p14 has the steps for gfm of whole hydrate)
% water = (part water/ whole hydrate) x100
% water = { [# water x (gfm of water)]/ gfm of the hydrate} x 100
ex.: What is the % water in CaSO42H2O ?
Part water = 2 x gfm of water = 2 [2(1.0) +16.0] g/mole = 36.0 g/mole
Whole is the gfm of CaSO42H2O:
GFM ofCaSO42H2O = [40.1 +32.1 4(16.0)]g/mole +2 [2(1.0)+16.0] g/mole
= 172.2 g/mole
% water = (36.0 g/mole/172.2 g/mole) x 100 = 20.9%
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Remember to show units & work! NO Work NO CREDIT!!!!
1. What is the % water in CuSO45H2O ?
# H2O x GFM of H2O:
% H 20 =
GFM of Whole hydrate:
2. What is the % water in BaCl22 H2O ?
# H2O x GFM of H2O:
% H 20 =
GFM of Whole hydrate:
3. What is the % water in CoCl26H2O?
# H2O x GFM of H2O:
% H 20 =
GFM of Whole hydrate:
V. Density of Gasses at STP:
From unit on the gas laws, we will learn that all gases at the same temperature, pressure
and volume have the same number of molecules. At STP (standard temperature and
pressure) 1 mole of any gas has a volume of 22.4 L. We can use this volume to calculate
the density of any gas. Since 1 mole of a gas is its gram formula mass (GFM), we can use
GFM of the gas for the mass and 22.4 L for volume in the density formula. We can also
determine the GFM of an unknown gas at STP if we know its density since its volume will
be 22.4 L!
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Look up on ref table T the density formula and write it below.
Example: What is the density of hydrogen gas (H2) at STP?
Step 1: Calculate the GFM
Gfm= 2(1.0) = 2.0 grams
(the moles would cancel out later, so just
use grams instead of g/mol)
Step 2: Use the density Formula
Volume at STP = 22.4 L/mol
D = 2.0 g/ 22.4 L = 0.089285714 g/L
D = 0.089 g/L
(the moles would cancel out later, so just
use Liters instead of L/mol)
1) What is the density of chlorine gas (Cl2) at STP?
Step 1: Calculate the GFM
Step 2: Use the density Formula
Volume at STP = 22.4 L
2) What is the density of fluorine gas (F2) at STP?
Step 1: Calculate the GFM
Step 2: Use the density Formula
Volume at STP = 22.4 L
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3) What is the density of methane gas (CH4) at STP?
Step 1: Calculate the GFM
Step 2: Use the density Formula
Volume at STP = 22.4 L
4) What is the density of ammonia gas (NH3) at STP?
Step 1: Calculate the GFM
Step 2: Use the density Formula
Volume at STP = 22.4 L
Rearranging the density formula, can allow you to calculate the gram formula mass of an
unknown gas. The volume is still 22.4 L and the density is given. In the following
problems you will solve for the mass in the density equation.
5) What is the gram formula mass of an unknown gas whose density at STP is 1.96 g/L ?
Step 1: Rearrange the density formula to
Step 2: Use this rearranged formula to
solve for mass.
solve for mass.
Volume at STP = 22.4 L
6) The density of a Noble Gas at STP is 5.86 g/L. What is its gram formula mass and
identity?
Step 1: Rearrange the
Step 2: Use this rearranged
Step 3: Look up on
density formula to solve
formula to solve for mass.
the PT !
for mass.
Volume at STP = 22.4 L