Stoichiometry: Chemical Reactions are like Recip

es

How much reactant is needed to make a certain amount of

product?

Dozen = 12

Case = 24

Ream = 500

Units A dozen eggs = 12 eggs A case of coke = 24 cans A ream of paper = 500 sheets A century = 100 years

In Chemistry, we use…Mole: It is a unit equal to 6.022 x 1023 ato

ms or molecules

This number is called Avogadro’s Number, in honor of Amadeo Avogadro.

How Big is a Mole?

-One mole of marbles would cover the entire Earth (oceans included) for a depth of three miles.-One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 milliontimes.

Molar Mass Molar Mass: The mass of 1

mole of substance. 1 mole of carbon contains

6.022 x 1023 atoms and has a mass of 12.0107 grams. Unit: g/mol Carbon’s molar mass is 12.01

g/mol

Molar Mass

ZnCl2:

1 Zn: 1 x 65.39 g/mol = 65.39 g/mol

2 Cl: 2 x 35.45 g/mol = 70.90 g/mol

Molar Mass: 136.29 g/mol

Molar Mass

ZnSO4:

1 Zn: 1 x 65.39 g/mol = 65.39 g/mol

1 S: 1 x 32.07 g/mol = 32.07 g/mol

4 O: 4 x 16.00 g/mol = 64.00 g/mol

Molar Mass = 161.46 g/mol

General Plan for Converting Mass, Amount, and Number of Particles

Mass of

substance

(grams)

Amount of

Substance in

Moles

Number of Atoms

or molecule

s

Use the molar mass

Use Avogadro

’s Number

Sample Problem 1.

A chemist has a jar containing 388.2 g of iron. How many moles of iron does the jar contain?

Sample Problem 2.

A student needs 0.366 mol of zinc for a reaction. What mass of zinc in grams should the student use?

Sample Problem 3.

How many moles of lithium are there in 1.204 x 1024 lithium atoms?

Chemical Equations are like

Cooking Recipes

Recipe makes 5 dozen cookies.

Velasquez has 5 eggs. How many dozens of cookies can she make?

3/4 c. brown sugar1 tsp vanilla extract2 eggs2 c. chocolate chips

2 1/4 c. flour1 tsp. baking soda1 tsp. salt1 c. butter3/4 c. sugar

5 eggs 5 doz.

2 eggs= 12.5 dozen cookies

“Mole Ratio” of eggs to cookies

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Recipe makes 5 dozen cookies.

Henkels has 9 cups of chocolate chips. How many dozens of cookies can he make?

3/4 c. brown sugar1 tsp vanilla extract2 eggs2 c. chocolate chips

2 1/4 c. flour1 tsp. baking soda1 tsp. salt1 c. butter3/4 c. sugar

5 eggs 5 doz.

2 eggs= 12.5 dozen cookies

“Mole Ratio” of eggs to cookies

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Proportional Relationships: S’more Activity2 Gc + 1 M + 4 Cp 1 Sm

If each student is to make one S’more, and I have 30 students, how many graham crackers & chocolate pieces will I need?

Given: 30 S’moresUnknown: ? Gc, ? Cp

30 S’mores 2 Gc

1 S’more

= ?

“Mole Ratio”

30 S’mores 4 Cp

1 S’more

= ?

“Mole Ratio”

Stoichiometry Diagram

Mass

Particles

VolumeMole

Mole

Mass

Volume

Particles

Given Unknown Substance A Substance B

Use periodic table

1 mole = m

olar mass (g)

Mole RatioUse coefficientsfrom balanced

chemical equation

1 mole = 22.4 LSTP

1 mol

e =

6.0

22 x 1

023 p

artic

les

(ato

ms or

mol

ecule

s)

1 mole = 22.4 L STP1 m

ole = 6.022 x 10 23

particles

(atoms or m

olecules)

Use p

erio

dic ta

ble

1 mol

e =

mol

ar

mas

s (g)

(gases) (gases)

Mole Ratio2Al2O3(l) 4Al(s) + 3O2(g)

2 molecules 4 atoms 3 molecules2 dozen 4 dozen 3 dozen2 moles 4 moles 3

moles-The coefficients of this equation tells us that for every

2 moles of aluminum oxide, it produces 4 moles of solid aluminum and 3 moles of oxygen molecules.

-The mole ratio, a conversion factor between two amounts in a chemical reaction. It is indicated by the coefficients of the chemical equation.

Mole Ratios:2 mol Al2O3 4 mol Al4 mol Al 2 mol Al2O3

2 mol Al2O3 3 mol O2

3 mol O2 2 mol Al2O3