chemistry week 26 please get out your calculator!
TRANSCRIPT
Chemistry Week
26
Please get out your calculator!
March 11, 2013
AGENDA:1 – Agenda/ Bell Ringer 2 – CN: Limiting
Reagent and Percent Yield
3 – Summary4 – Classwork Time
Today’s Goal:Students will be able to
determine a limiting reactant and calculate a percent yield.
Homework1. Stoichiometry and
Limiting Reactant.2. If you missed Friday’s
Quiz you must come make it up by Friday.
Monday, March 11th
Objective: Students will be able to determine a
limiting reactant and calculate a percent yield.
Bell Ringer: 2 C4H10 + 13 O2 8 CO2
+ 10 H2O
How many grams of H2O are formed from 5.5 g of O2?
5.5g O2 x ______ x ______ x ______ = g H2O
30 seconds Remaining…
Monday, March 11th
Objective: Students will be able to determine a
limiting reactant and calculate a percent yield.
Bell Ringer: 2 C4H10 + 13 O2 8 CO2
+ 10 H2O
How many grams of H2O are formed from 5.5 g of O2?
5.5g O2 x ______ x ______ x ______ = g H2O
March 11, 2013
AGENDA:1 – Agenda/ Bell Ringer 2 – CN: Limiting
Reagent and Percent Yield
3 – Summary4 – Classwork Time
Today’s Goal:Students will be able to
determine a limiting reactant and calculate a percent yield.
Homework1. Stoichiometry and
Limiting Reactant.2. If you missed Friday’s
Quiz you must come make it up by Friday.
Monday, March 11th
Objective: Students will be able to determine a
limiting reactant and calculate a percent yield.
Bell Ringer: 2 C4H10 + 13 O2 8 CO2
+ 10 H2O
How many grams of H2O are formed from 5.5 g of O2?
5.5g O2 x 1mol O2 x 10molH2O x 18 g H2O =
32 g O2 13 mol O2 1mol H2O
2.4 g H2O= 5.5 x 1 x 10 x 18 g H2O =32 x 13 x 1
Obj: SWBAT determine a limiting reactant and calculate a percent yield.
Date: 3/11/2013What is
a Limitin
gReacta
nt?
• In a chemical reaction, the amount of product that can be produced is limited by the reactant that can produce the least amount of products based upon the ratios in which they react.
• The reactant that produces the least amount of product is called the limiting reactant.
Example
How many bikes can be made if you have:• 18 wheels• 10 handlebars• 12 seats• 10 frames
• You can make 9 bikes• Wheels are the
limiting reactant.
Example #1
All limiting reactant problems start with a balanced chemical equation.
4 FeCl3 + 3 O2 2 Fe2O3 + 6 Cl2
How many moles of Cl2 can be produced if 5 moles of FeCl3 react with 4 moles of O2?5 mol FeCl3 x
6 mols Cl2 =
4 mols FeCl3
7.5 mol Cl2
4 mol O2 x 6 mols Cl2 =
3 moles O2
8 mol Cl2
• FeCl3 is the limiting reactant because 7.5 moles of Cl2 were produced.
• O2 was the excess reactant.
Example #2
2 C2H6 + 7 O2 4 CO2 + 6 H2O
How many grams of H2O can be produced if 15 grams of C2H6 react with 45 grams of O2?
Molar masses: C2H6 = 30 g/mol; O2 = 32 g/mol; H2O = 18g/mol15 g C2H6
x
1mol C2H6 x30 g C2H6
6 mol H2O x
2 mol C2H645 g O2 x 1 mol O2 x
32 g O2
21.7 g H2O
• O2 is the limiting reactant• C2H6 is the excess reactant
18 gH2O =1 mol H2O
27 g H2O
6 mols H2O x
4 moles O2
18 g H2O =
1 mol H2O
What is Percent Yield?
• The ratio of the actual yield (what you actually produced) to the theoretical yield (what you calculated) for a chemical reaction expressed as a percentage.
• It’s a measure of the efficiency of the reaction. (think of it like a grade for the reaction)Exampl
e
Percent Yield = Actual Value x 100 Theoretical ValueWhat would be the percent yield of the previous reaction if only 20 g of H2O were produced?Percent Yield = 20 g H2O x 100 = 21.7 g H2O
92.2 %
Obj: SWBAT determine a limiting reactant and calculate a percent yield.
Date: 3/11/2013
Set-Up Help
Balanced Chem Eq: aA bB1. Calculate the molar masses of both
compounds in the problem2. Convert: remember Given and WantGiven(g) x1 mol Given x mol Want x Mol.mass Want =
Mol.mass Given mol Given 1 mol Want3. Multiply everything in numerator. 4. Multiply everything in the denominator5. Divide Numerator by Denominator.
Set-Up Help
Balanced Chem Eq: aA bB Mole A Mole B Gram B:Mole A x b Mole B x Molar Mass B = Gram B
a Mole A 1 mol B
Gram A Mole A Mole BGram A x 1Mole A x b Mole B = Mole B
Molar Mass A a mol A