Simplified for May 2013 – Stoi–chi–o–met–try – – Stoi–chi–o–met–try – (Rhymes with “toy-key-ah-met-tree”) (Rhymes with “toy-key-ah-met-tree”) Stoichiometry–

Simplified for May 2013Simplified for May 2013

– – Stoi–chi–o–met–tryStoi–chi–o–met–try – – (Rhymes with “toy-key-ah-met-tree”)(Rhymes with “toy-key-ah-met-tree”) Stoichiometry– The Mole Concept Applied Stoichiometry– The Mole Concept Applied

To Balanced Chemical Equations!To Balanced Chemical Equations!

1. In a factor label problem, 1. In a factor label problem, twotwo substances from the balanced chemical substances from the balanced chemical equation are picked to work with. One of equation are picked to work with. One of the substances will be used as the “the substances will be used as the “givengiven” ” in your word problem, and the other in your word problem, and the other substance will show up as the “want to substance will show up as the “want to know” in your word problem.know” in your word problem.

2. Since the 2. Since the coefficientscoefficients of the chemical of the chemical equation have the unit, “equation have the unit, “molemole”, the ”, the coefficients establish the proportions coefficients establish the proportions (ratios) in (ratios) in molesmoles, that exist between the , that exist between the substances reacting in, and being substances reacting in, and being produced during, a chemical reaction. produced during, a chemical reaction.

3. Until now you were focused on one particular 3. Until now you were focused on one particular substance, and/or the atoms within its formula, substance, and/or the atoms within its formula, for each word problem; but, now you must work for each word problem; but, now you must work with 2 substances for each word problem. The with 2 substances for each word problem. The coefficients will be used as one of your coefficients will be used as one of your factors factors (fractions), and it will be called the (fractions), and it will be called the “mole ratio”“mole ratio” factor. factor.

The The mole ratiomole ratio factor is the only way that you factor is the only way that you may convert (or move) between the one may convert (or move) between the one “given” substance, and the other “want to “given” substance, and the other “want to know” substanceknow” substance. .

4. All of the other parts of the “4. All of the other parts of the “mole road mole road mapmap” still apply to the substances in the ” still apply to the substances in the chemical equation, and are used within a chemical equation, and are used within a stoichiometry problem to convert between stoichiometry problem to convert between molar mass, molar volume, and molar mass, molar volume, and Avogadro’s number for any of the Avogadro’s number for any of the substances in the chemical equation.substances in the chemical equation.

Guided PracticeGuided Practice: :

Given chemical equation:Given chemical equation:

2 Na + Cl2 Na + Cl22 ––> 2 NaCl ––> 2 NaCl

What is the mole ratio between Na and ClWhat is the mole ratio between Na and Cl22??

Answer: Answer: 2 moles Na = 1 mole Cl2 moles Na = 1 mole Cl22

6. What would be the conversion factor 6. What would be the conversion factor necessary in order to convert necessary in order to convert from moles of Nafrom moles of Na to moles of Clto moles of Cl22??

2 Na + Cl 2 Na + Cl22 ––> 2 NaCl ––> 2 NaCl

Namoles

Clmolex

2

.1 2

Na moles 2

Cl mole 1x 2


Given that 34 moles Na reacted, calculate how Given that 34 moles Na reacted, calculate how many moles Cl2 also reacted.many moles Cl2 also reacted.

Namoles

Clmolex

2

.1 2

22 Cl moles 17

Na moles 2

Cl mole 1 x Na moles 34

8. 8. Your TurnYour Turn: Using the above chemical : Using the above chemical equation, if 79.21 moles of NaCl are equation, if 79.21 moles of NaCl are produced, how many moles of Na reacted produced, how many moles of Na reacted during?during?



8. 8. Your TurnYour Turn: :

given: 79.21 moles of NaCl given: 79.21 moles of NaCl

Want to know: moles of NaWant to know: moles of Na

Na moles 79.21 NaCl moles 2

Na mole 2 x NaCl moles 79.21

Putting It togetherPutting It together: Using the above : Using the above chemical equation, if 79.21 moles of NaCl chemical equation, if 79.21 moles of NaCl are produced, what is the are produced, what is the massmass of Na that of Na that reacted during the reaction? reacted during the reaction?

You will need to use 2 factors!You will need to use 2 factors!


Putting It togetherPutting It together: : Given 79.21 Given 79.21 molesmoles of NaCl of NaCl Want to know Want to know massmass of Na of Na You will need to use 2 factors!You will need to use 2 factors!


Na grams 182 Na mole 1

Na grams 22.99 x

NaCl moles 2

Na mole 2 x NaCl moles 79.21

Mole ratio (coefficients)

Molar mass.

10. Using the above equation, if 79.21 10. Using the above equation, if 79.21 moles NaCl are produced, what is moles NaCl are produced, what is the the volumevolume of diatomic chlorine gas (Cl of diatomic chlorine gas (Cl22)) that that

reacted? reacted?


10. Given: 79.21 moles NaCl 10. Given: 79.21 moles NaCl Want to knowWant to know volumevolume of diatomic chlorine gas of diatomic chlorine gas

(Cl(Cl22))


22

22 Cl L 887 Cl mole 1

Cl Liters 22.4 x

NaCl moles 2

Cl mole 1 x NaCl moles 79.21

11. Using the above equation, if 11. Using the above equation, if 8.32 x 10 8.32 x 10 2525 atomsatoms of Cl of Cl are produced are produced, how many , how many moles of Namoles of Na reacted during the reaction? reacted during the reaction?

You will need 3 factors!You will need 3 factors!


Given: 8.32 x 10 Given: 8.32 x 10 2525 atomsatoms of Cl of Cl

Want to know:Want to know: moles of Na moles of Na


Na moles 138. Cl mole 1

Na moles 2

Cl mole 2

Cl mole 1

Cl atoms10 x 6.02

Cl mole 1 x Cl atoms 10 x 8.32

2

223

25

Mole ratio (coefficients)

Avogadro’s number

Formula Change

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Simplified for May 2013 – Stoi–chi–o–met–try – – Stoi–chi–o–met–try – (Rhymes with “toy-key-ah-met-tree”) (Rhymes with “toy-key-ah-met-tree”) Stoichiometry–