** Refer to

atomic mass

on Periodic Table!!! **

Review

***

a.) 1 a.m.u.

=

1/12

the mass of a ____________ atom

b.) subscript

=

#

of ____________.

Eg.

How many total atoms in

calcium nitrate

?

MOLES

* In Chemistry, we count using moles.*

•

1 Mole

=

6 x 10 23

atoms (particles). •

(1 mole = # of atoms present in 12g of C-12)

Mole vs. Dozen

• To understand “moles” better, we should

compare

1 mole

and

1 dozen

.

•

Q.1. How many apples are in 1 dozen?

•

Q.2. How many atoms are in 1 mole?

•

Q.3. Which has a greater mass, 1 dozen apples or 1 dozen grapes?

•

Q.4. Which has a greater mass, 1 mole of sodium atoms or 1 mole of mercury atoms?

Many names, same concept!

Mass of 1 Mole

= • “

gram atomic mass

”, • “

gram formula mass

”, • “

molar mass

”, • “

formula weight

”, • “

gram molecular mass

”.

Practice

–

Use Periodic Table

•

Eg.

1.)

1 atom

of

H 1 mole

of

H

= 1 a.m.u.

= 1g.

2.)

1 atom

of

C 1 mole

of

C

= 12 a.m.u.

= 12g.

3.)

1 atom

of

Mg

= _____________

1 mole

of

Mg

= _____________ 4.)

2 atoms 2 moles

of

Mg

of

Mg

(or, “

Mg 2

”) = _______________ = ___________ 5.)

1 molecule 1 mole

of

CO 2

of

CO 2

= ____________ = ______________

Atomic Mass

•

Atomic mass – The sum total mass of all present atoms (in a.m.u.

) ** Always give your answer as specific as the question suggests. **

Atomic Mass

Eg.

Give the

atomic mass

for all of the following to the

nearest tenth

. . . 1.)

KCl

2.)

Ca 3 N 2

3.)

(NH 4 ) 2 S

4.)

CCl 4

Gram formula mass

•

Gram formula mass (gfm) (a.k.a. “molecular mass” or “formula mass”)

• the

sum total mass

using grams (

g

) instead of

a.m.u.

• (gfm) always equals 1 mole (mol) of a compound **(

gfm = 1 mole

) *** Q.1. How many molecules are in 1 mole?

Practice

Eg.

Give

a.)

the

total # of atoms

and

b.)

the

gram formula mass (gfm)

for each of the following (

round to whole #

) 1.)

NaCl

2.)

F 2

3.)

K 2 CO 3

4.)

Al(OH) 3

5.)

C 6 H 12 O 6

Hydrates

•

Hydrates:

– Ionic compound with

water

(

H 2 O

) attached.

–

Hydrate

= crystals that contain water molecules.

–

Anhydrous

= substance without water molecules.

Hydrates

Q.1

What is the

mass

of

1 mole

of

H 2 O

(the

gfm

of

H 2 O

)?

Q.2

What is the gram formula mass (

gfm

) of

5 H 2 O

?

Hydrates

• Give the

gram formula mass (gfm)

the following

Hydrates

: for each of

“ ∙ ” = “+”

1.)

CuSO 4 ∙ 5H 2 O

2.)

NiSO 4 ∙ 6H 2 O

3.)

MgCl 2 ∙ 2H 2 O

Mole-Mass Conversions

Total mass (g) = (# of Moles) x (gfm)

Eg.1 What is the

mass

of

3 moles

of

H 2 SO 4

?

Total mass

= (

3 mol

)(

gfm

of

H 2 SO 4

) =_____________ Eg.2 What is

mass

of

.5 moles

of

copper(II) sulfate

?

Eg.1 How many

moles

are there in

88g

of

CO 2

?

Step 1: find the gfm of CO 2 Step 2: solve the equation Eg.2 How many moles are there in 72g of CH 4

Practice Problems

• 1.) What is the

mass

of

2 moles

of

iron(II) nitrite

?

• 2.) How many

moles

are in

46g H 2 SO 4

?

• 3.) What is the

mass

of

0.5 mol carbon dioxide

?

• 4.) How many

moles

are in

544g CaSO 4

?

% Composition

1.) What is the % composition of oxygen in H 2 O?

2.) What is the % composition of hydrogen in H 2 O?

% Composition

•

% Composition

=  

mass

_

of Total

_ _

part mass

 

x

100 %

Eg.1 What is the

% composition

of

Carbon

in

CO 2

?

Step 1: Step 2: Step 3:

get the

gfm

of

C

(“part”) get the

gfm

of

CO 2

(“total”) plug into equation and

solve

.

• Eg.2 Find the

% composition

of

C

,

H

, and

O

in

C 6 H 12 O 6

.

• Eg.3 What is the

% composition CuSO 4 ∙ 5H 2 O

?

of

water

in • Eg.4 What is the

% water

in

NiSO 4

What is the %

Ni

?

∙ 6H 2 O

?

The Element Song

The Element Song

Empirical vs. Molecular Formula

Molecular Formula C 6 H 6 CO 2 C 6 H 12 O 6 C 2 H 4 C 6 H 12 O 11 Empirical Formula CH CO 2 CH 2 O CH 2 C 6 H 12 O 11

Empirical Formula

Empirical Formula

•

Q.

How do we get the Empirical Formula from the Molecular Formula???

** Fill in the

Empirical Formula

for each of the following:

Molecular Formula

C 2 H 2 C 4 H 10 C 5 H 10 C 5 H 9 C 3 H 9 O 3

Empirical Formula

Converting Empirical Formula



Molecular Formula:

Steps

:

1. Identify

the mass of the molecular formula (given)

2. Calculate

the

gfm

of

Empirical formula.

3. Divide molecular mass

(step 1) by

empirical mass

(step 2) and record answer.

x

=  

molecular empirical

_ _

mass mass

 

4. Multiply subscripts

of Empirical formula by the answer in step 3 to get the Molecular formula.

Eg.1: The molecular mass of a substance is

48 a.m.u.

and its empirical formula is

CH 4

. What is the

molecular formula

of this substance?

Eg.2: What is the molecular formula of a substance with a molecular mass of

30g

and an empirical formula of

CH 3

?

Eg.3: A substance has an empirical formula of

CH 2 O

and a molecular mass of

180g

. What is the molecular formula of this substance?

Eg.4: A substance has an empirical formula of

CO 2

and a molecular mass of

44g

. What is the molecular formula of this substance?

Stoichiometry and Balancing Equations

**Chemical Equations – used to represent chemical reactions.

•

In all chemical rxns., 3 types of Conservation take place: 1.) Mass 2.) Energy (Kinetics) 3.) Charge (#e- lost = #e- gained (Redox.))

**Important . . .

Symbol



,



,



, and = Meaning “yield”; separates reactants from products

Stoichiometry

** Stoichiometry – branch of chemistry that deals with the amounts of substances that enters (reactants) and leaves (products) a chemical reaction. **

Stoichiometry

•

Coefficients = # moles of a compound

–

Eg.

5 _

BaCl 2

=

5

moles of

BaCl 2

•

Subscripts = # moles of atoms (inside of a compound)

–

Eg.

3 _

Al 2 S 3

=

____

moles of the compound

Al 2 S 3

,

_____

moles of

Aluminum

atoms and

____

moles of

Sulfur

atoms.

Stoichiometry

1.) __

Na

+ __

O 2

 __

Na 2 O

SOC = 2.) __

Al

+ __

O 2

 __

Al 2 O 3

SOC =

Stoichiometry

3.)

carbon + oxygen



carbon dioxide

SOC =

**Remember “ BrINClHOF ”!!!**

4.)

hydrogen + oxygen



water

SOC =

Stoichiometry

___ AlCl 3 + ____AgNO 3



____AgCl + ____Al(NO 3 ) 3

Link – Balancing Equations (timed) Link 2 – Balancing Equations Handout

Stoichiometry

Rule: 1.) If you change any coefficient in a balanced equation, you MUST change them all.

2.) To change coefficients, you must either multiply or divide by a number.

Stoichiometry

Eg.1: ___KClO 3



____KCl + ____O 2

How many

moles

of Oxygen gas will be produced if you decompose

4 moles

of KClO 3 ?

Stoichiometry

Eg.2: ___Zn + ___CuCl



___ZnCl 2 + ___Cu

How many

moles

of CuCl were used if

10 moles

of copper metal were produced?

Stoichiometry

Eg.3: ___ AlCl 3 + ____AgNO 3



____AgCl + ____Al(NO 3 ) 3

How many

moles

of aluminum chloride must you use in the above reaction to produce

1.5 moles

of silver chloride?