** 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 1023 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 a.m.u.

1 mole of H = 1g.

2.) 1 atom of C = 12 a.m.u. 1 mole of C = 12g.

3.) 1 atom of Mg = _____________ 1 mole of Mg = _____________

4.) 2 atoms of Mg (or, “Mg2”) = _______________ 2 moles of Mg = ___________

5.) 1 molecule of CO2 = ____________ 1 mole of CO2 = ______________

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 MassEg. Give the atomic mass for all of the following to the nearest tenth . . .

1.) KCl

2.) Ca3N2

3.) (NH4)2S

4.) CCl4

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?

PracticeEg. Give a.)the total # of atoms and b.)the gram formula mass (gfm) for each of the following (round to whole #)

1.) NaCl

2.) F2

3.) K2CO3

4.) Al(OH)3

5.) C6H12O6

Hydrates• Hydrates:

– Ionic compound with water (H2O) attached.

– Hydrate = crystals that contain water molecules.

– Anhydrous = substance without water molecules.

Hydrates

Q.1 What is the mass of 1 mole of H2O

(the gfm of H2O)?

Q.2 What is the gram formula mass (gfm) of 5 H2O?

Hydrates• Give the gram formula mass (gfm) for each of

the following Hydrates:

1.) CuSO4 ∙ 5H2O “ ∙ ” = “+”

2.) NiSO4 ∙ 6H2O

3.) MgCl2 ∙ 2H2O

Mole-Mass Conversions

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

Eg.1 What is the mass of 3 moles of H2SO4?

Total mass = (3 mol)(gfm of H2SO4) =_____________

Eg.2 What is mass of .5 moles of copper(II) sulfate?

Eg.1 How many moles are there in 88g of CO2?

Step 1: find the gfm of CO2

Step 2: solve the equation

Eg.2 How many moles are there in 72g of CH4

Practice Problems• 1.) What is the mass of 2 moles of iron(II) nitrite?

• 2.) How many moles are in 46g H2SO4?

• 3.) What is the mass of 0.5 mol carbon dioxide?

• 4.) How many moles are in 544g CaSO4?

% Composition

1.) What is the % composition of oxygen in H2O?

2.) What is the % composition of hydrogen in H2O?

% Composition

• % Composition = %100___ xmassTotalpartofmass

Eg.1 What is the % composition of Carbon in CO2?

Step 1: get the gfm of C (“part”)Step 2: get the gfm of CO2 (“total”)

Step 3: plug into equation and solve.

• Eg.2 Find the % composition of C, H, and O in C6H12O6.

• Eg.3 What is the % composition of water in CuSO4 ∙ 5H2O?

• Eg.4 What is the % water in NiSO4 ∙ 6H2O? What is the % Ni?

The Element Song

The Element Song

Empirical vs. Molecular Formula

Molecular Formula Empirical FormulaC6H6 CH

CO2 CO2

C6H12O6 CH2O

C2H4 CH2

C6H12O11 C6H12O11

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 Empirical Formula

C2H2

C4H10

C5H10

C5H9

C3H9O3

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 =

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

massempiricalmassmolecular

__

Eg.1:The molecular mass of a substance is 48 a.m.u. and its empirical formula is CH4.

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 CH3?

Eg.3:A substance has an empirical formula of CH2O

and a molecular mass of 180g. What is the molecular formula of this substance?

Eg.4:A substance has an empirical formula of

CO2 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 Meaning

, , , and = “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 _BaCl2 = 5 moles of BaCl2

• Subscripts = # moles of atoms (inside of a compound)– Eg. 3 _Al2S3 = ____ moles of the compound Al2S3,

_____ moles of Aluminum atoms and ____ moles of Sulfur atoms.

Stoichiometry

1.) __ Na + __ O2 __ Na2O SOC =

2.) __ Al + __ O2 __ Al2O3 SOC =

Stoichiometry

3.) carbon + oxygen carbon dioxide SOC =

**Remember “BrINClHOF”!!!**

4.) hydrogen + oxygen water SOC =

Stoichiometry

___ AlCl3 + ____AgNO3 ____AgCl + ____Al(NO3)3

Link – Balancing Equations (timed)

Link 2 – Balancing Equations Handout

StoichiometryRule:

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.

StoichiometryEg.1: ___KClO3 ____KCl + ____O2

How many moles of Oxygen gas will be produced if you decompose 4 moles of KClO3?

StoichiometryEg.2:

___Zn + ___CuCl ___ZnCl2 + ___Cu

How many moles of CuCl were used if 10 moles of copper metal were produced?

StoichiometryEg.3:

___ AlCl3 + ____AgNO3 ____AgCl + ____Al(NO3)3

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

1.5 moles of silver chloride?