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Stoichiometry - COMBINATIONS OF ELEMENTS AND THEIR REACTIONS:  Study chemical reactions by reading This is an example of a chemical reaction and a reversal.sections on stoichiometry in chemistry text books and demonstrating them with laboratory experiments.  (See laboratory cautions below). Combining elements to form new combinations is a very important part of chemistry. (If you don't know the meaning of the words here look them up in the "TERMS" links provided below.  Also look up the words in your dictionary for additional understanding.)  Learn about the concept of a MOLE.  Learn more about chemical reactions HERE.

In a simple equation, such as the synthesis of iron(II) sulfide,
iron + sulfur = iron(II) sulfide the equation requires no special balancing:

Fe + S     FeS

Our last stage is to put in state symbols, (s, l, g, aq), as appropriate.

Fe(s) + S(s)     FeS(s)

On a molar basis, we can say that one mole of iron (56g) reacts with one mole of sulfur (32g) to produce one mole of the compound iron(II) sulfide (88g).

You will need the ability in chemistry to describe formulas for any substance you come across.  For ionic compounds the compound formula may be arrived at by knowing the number of charges each ion has.  Memorize this table.  For example sodium (Na) has a charge of +1.  Oxygen (O) has a charge of -2.  Carbon (C) has a charge of -4.  When you see these elements in a formula; substitute the charge numbers and that will tell you how many atoms of each element are needed to balance the equation.

For example if you combine sodium (Na) and chlorine (Cl) that is the same as +1 = -1 = 0 so you only need one of each.  When we say one, it could mean one atom or one mole.  So the formula for  a combination of sodium and chlorine is Na+Cl- or often written with out the superscripts as NaCl.   This is sodium chloride or common table salt.  What about aluminum and chlorine?  +3 = -1 = +2  In this case you need two chlorine (whatever) to balance the equation for the compound.  It would end up as Al3+ 3 Cl- which is AlCl3.  Some elements can have various charges like iron.  They are written with roman numerals to indicate the charge; iron(II) Fe2+, iron(III) Fe3+, etc.


Reactions http://web.jjay.cuny.edu/~acarpi/NSC/6-react.htm
Graphics http://ull.chemistry.uakron.edu/genobc/Chapter_05/
Key Points http://www.chem4kids.com/files/react_intro.html
Common types of reactions http://www.towson.edu/~ladon/react.html
Predicting reactions http://www.spusd.k12.ca.us/chemmybear/preactions.html
Chemical Reactions
Chemistry Experiments you can do at home - http://www.bxscience.edu/~chinyu/2690/exper/exper.htm
Lab Books Online - Phoenix College  http://chemlab.pc.maricopa.edu/labbooks/default.html
Lucid stoichiometry (LSU)
Hints for solving stoichiometry problems (Widener U)
Stoichiometry: mass-mass problems (ChemCentral)
Stoichiometry worksheet (Georgetown College)
Stoichiometry introduction (limiting reagent) (Carnegie Mellon)
Stoichiometry (limiting reagent simulation)
Stoichiometry 1 (Wilton High School)
Stoichiometry 2
(Wilton High School)
Stoichiometry 3 (Wilton High School)
Stoichiometry 4 (Wilton High School)
Stoichiometry (DBHS)
Stoichiometry by the recipe (John Brodemus)
Stoichiometry applet (IrYdium Project)*
Stoichiometry notes (Erik)
What is stoichiometry (Floyd College)
Chemical reaction stoichiometry web site (Smith)
Mass relationships in chemical equations (CSU-DH)
Stoichiometry online (GSU)
BioChemisty/MicroChemistry Software Downloads.
Good Chemistry Tutorial Site
High School Chemistry Tutorials Complete


Press the > button to play the video!

Polyatomic Ions
Formula Name Formula Name
C2H3O2- acetate ion NO3- nitrate ion
NH4+ ammonium ion Cl4- perchlorate ion
CO32- carbonate ion PO43- phosphate ion
CN- cyanide ion SiO44- silicate ion
HCO3- bicarbonate ion SO42- sulfate ion
OH- hydroxide ion SO32- sulfite ion

balancing equations by counting atoms (Wilton High School)
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balancing equations by the method of ox-red (Wilton High School)
balancing equations worksheet (Wilton High School)
the meaning of a chemical equation (Chem Team)
the meaning of chemical equations (Ohio State)
how can I balance an equation?
balancing chemical equations (Fordham Prep)
balancing equations-student page (Fordham Prep)
balancing equation (University of Nebraska-Lincoln)
balancing equations (Chem 111)
balancing equations (Hawaii) 
balancing equations (School Chem) 
balancing chemical equations (Chem Team)
balancing chemical equations (Logan)
balancing chemical equations (Howe HS)
balancing chemical reactions (Ian Wigle)
balancing chemical reactions (CSU-DH)
a tutorial on balancing chemical equations (Ohio State)

chemical equations (Markham HS)
a chemistry equation balancing mystery (Ohio State)
practice balancing equations (Roanoke Valley Governor's School)
chem balancer game Sulan Dun
worksheet : balancing equations Sulan Dun
balancing equations activity (George Washington HS) 
balancing chemical equations quiz (Tennessee Tech) 
exploring the meaning of chemical reactions (Ohio State)
balancing by inspection (Ohio State) 
another example of balancing by inspection (Ohio State)
some chemical equations cannot be balanced (Ohio State)
combustion equations (Barnard)
Chemical Equations, Oxidation States and Balancing of Equations (KiwiWeb, NZ)
chemical equations 1 (Aufbau1)
chemical equations 2 (Aufbau1)
interactive tutorial on balancing equations Yue-Ling Wong
writing and balancing chemical equations (Mr. Hall)

stoichiometry 1 (Wilton High School)
stoichiometry 2 (Wilton High School)
stoichiometry 3 (Wilton High School)
stoichiometry 4 (Wilton High School) 
what is stoichiometry? (Chem Team) 
what is stoichiometry (Floyd College) 
what is stoichiometry (UCDSB)
introduction to stoichiometry (Kathy Beeler)
stoichiometry (Chem Team) 
stoichiometry (KiwiWeb)
stoichiometry (Applewoods Heights Secondary School)
stoichiometry (Chem4Kids)
stoichiometry (Hympton-Sydney College)
stoichiometry (Floyd College)
stoichiometry by the recipe (John Brodemus)
stoichiometry applet (IrYdium Project)*
stoichiometry (CSU-Stanislaus) 
stoichiometry (Purdue) 
stoichiometry (Matthew Shepard)
stoichiometry (Howe HS)
stoichiometry (Takalah)
stoichiometry (North Middlesex Regional HS)
stoichiometry (University of Wisconsin)
stoichiometry (Marymount)
stoichiometry (Clackamas CC)
stoichiometry part 1 (Penn State-York) 
stoichiometry part 2 (Penn State-York) 
stoichiometry part 3 (Penn State-York) 
stoichiometry part 4 (Penn State-York) 
stoichiometry notes (Erik)
stoichiometry online (GSU)
Lucid stoichiometry (LSU)
beginner's guide to stoichiometry web site (stoichiometry.net)
chemical stoichiometry (University of Waterloo)
molar stoichiometry (Plambeck) 
molar stoichiometry (University of Nebraska-Lincoln)

 moles, percents, and stoichiometry (Chem Tutor) 
quantitative information from balanced equations (Markham HS)
stoichiometry hints (Kathy Beeler) 
stoichiometry menu (UCDSB)
stoichiometry spreadsheet (the catalyst)
stoichiometry skeletons (The Catalyst)
stoichiometry: mass-mass problems (ChemCentral)
mass relationships in chemical equations (CSU-DH)
stoichiometric calculations: amounts of reactants and products (SUNY Binghampton)
stoichiometry problems (Logan)
stoichiometry problem solving (Purdue)
stoichiometry: chemical arithmetic formula conventions (ChemmyBear) 
stoichiometry worksheet (Bishop's College High School)
stoichiometry worksheet (Georgetown College) 
stoichiometry quiz (Tennessee Tech) 
the double Y diagram for solving stoichiometry problems (Chem Place)
stoichiometry by the recipe (Brodemus)
equations, formulas, and stoichiometry (Logan)
chemical reaction stoichiometry web site (Smith)
stoichiometry introduction (limiting reagent) (Carnegie Mellon)
stoichiometry (limiting reagent simulation) (Carnegie Mellon)
limiting reactants (Markham HS) 
hints for solving stoichiometry problems (Widener College)
limiting reagent problem set (Widener) 
limiting reactants (Markham HS)
limiting reagent and theoretical yield (Logan)
limiting reagent demos (University of Arizona)

REACTIONS MOVIE: http://video.google.com/videoplay?docid=393752449958147696&q=genre%3Aeducational

Polyatomic Ion Links:

Polyatomic Ions
Polyatomic Ion Calculator
Table of Common Polyatomic Ions
Polyatomic ions
General Chemistry Online: Companion Notes: Compounds: Polyatomic .
Table of Common Polyatomic Ions - Chemistry - Chemistry
Quia - Polyatomic Ions
CHEMystery: Reference: Oxidation States for Common Polyatomic Ions
Polyatomic ion - Wikipedia, the free encyclopedia

Copper (II) Bromide http://www.webelements.com/webelements/compounds/text/Cu/Br2Cu1-7789459.html


Some Common Polyatomic Ions

Ammonium NH4+ Chlorate ClO3- Peroxide O2-2
Acetate CH3COO- Perchlorate ClO4- Chromate CrO4-2
Nitrate NO3- Permanganate MnO4- Dichromate Cr2O7-2
Nitrite NO2- Carbonate CO3-2 Silicate SiO3-2
Hydroxide OH- Sulfate SO4-2 Phosphate PO4-3
Hypochlorite ClO- Sulfite SO3-2 Arsenate AsO4-3
Chlorite ClO2- Thiosulfate S2O3-2 Arsenite AsO3-3
Cyanate CN- Thiocyanate SCN- Borate BO3-3
Bicarbonate HCO3- Bisulfate HSO4- Bisulfite HSO3-


Now that we know something about the make up of compounds lets look at a reaction formula.  Suppose you add sulfuric acid to sodium bicarbonate and obtain as products carbon dioxide gas, sodium sulfate, and water.

NaHCO3  +  H2SO4          CO2    +    Na2SO4    +    H2O

Notice in order to form a molecule of sodium sulfate you must put in two sodium atoms.  To get two sodium atoms you need two molecules of sodium bicarbonate.  Therefore, the "balanced" equation becomes:

2 NaHCO3    +    H2SO4          2 CO2    +    Na2SO4    +    2 H2O

You should also know something about the prefixes used.  Here is a table to help you.

Greek Prefixes      
Prefix Number Prefix Number
mono- one hexa- six
di- two hepta- seven
tri- three octa- eight
tetra- four nona- nine
penta- five deca- ten


1.  Write the unbalanced equation.

            H2SO4    +   Al          Al2(SO4)3  +  H2

2.  Balance the equation.

            3H2SO4  +   2Al         Al2(SO4)3  +  3H2

3. Convert the known masses of the molecules to moles using molecular weight form the periodic table.

             H2SO4:  5x10-1 / 98.079 (g/mol) = 5 x 10-3 moles

4.  Use the balanced equation to set up mole ratios.

            3 mol (H2SO4):   2 mol (Al):   1 mol (Al2(SO4)3):   3 mol (H2)

5.  Use the mole ratios to calculate the number of moles of the desired reactant or product.  If the mass or the mole of only one species in the equation is known, use it to calculate the rest according to the coefficient (mole ratios) of the equation.  Otherwise, find the limiting reagent and use it to calculate the rest.  Since only the moles of H2SO4 is known we multiply it by the corresponding ratio to obtain the moles for other species.

            H2SO4:        5 x 10-3 moles

            Al:                 3 x 10-3  moles

            Al2(SO4)3:    2 x 10-3   moles

            H2:                 5 x 10-3  moles

6.  Convert from moles back to grams using molecular weights.

            H2SO4:        5 x 10-3 moles x 98.07 (g/mol)        =  5 x 10-1 g    

            Al:                 3 x 10-3 moles x 26.98154 (g/mol)  = 9 x 10-2 g       

            Al2(SO4)3:    2 x 10-3 moles x 342.154 (g.mol)    =  6 x 10-1 g     

            H2:                 5 x 10-3 moles x 2.01588 (g/mol)    = 1 x 10-2 g     

Famous scientist quote:
"In many carefully made experiments, Volta has observed that two metals put in contact become electric, and that this is the cause of the phenomena of the electric pile.  Davy later showed that this electrical state increases due to force of mutual affinities of the bodies used, and that this effect can be produced, and even seen, by means of certain precautions, in all bodies which have affinity for each other."  Jons Jakob Berzelius (1779 - 1848)

LEWIS DOT STRUCTURE http://video.google.com/videoplay?docid=5399558061059901856&q=chemistry


ACID and BASE Chemistry http://www.shodor.org/UNChem/basic/ab/
What are ACIDS? http://www.purchon.com/chemistry/acids.htm
History of Acids and Bases http://www.bbc.co.uk/dna/h2g2/alabaster/A708257
The Acids, Alkalis and Salts Crossword http://www.creative-chemistry.org.uk/funstuff/xword/acids.htm
ABOUT Acids and Bases http://chemistry.about.com/cs/acidsandbases/
Acids and Alkalis  http://www.gcsechemistry.com/aa.htm
Acids and Bases http://sciencespot.net/Pages/kdzchem3.html
AMINO Acids http://www.chemie.fu-berlin.de/chemistry/bio/amino-acids_en.html
AP Acids http://www.chemistrygeek.com/c2c15.htm
Properties and Examples http://qldscienceteachers.tripod.com/junior/chem/acid.html

Chem4Kids.com:Reactions:Acids and Bases
Acids & Bases Problem Set
Acids and Bases
Exploring Acids and Bases
Acids & Bases
Acids Bases and Salts
CHEMystery: Acids and Bases
Acids and Bases
Acids & Bases

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