Mass to Volume Conversion

- At a specific pressure and temperature one mole of any gas occupies the same volume.

- At 0 degrees Celsius and 101.3 kilo Pascals 1 mol = 22.4 L

- This temperature and pressure is called STP

- 22.4 L/ mol is the molar volume at STP

Example:

How many litres will 2.5 mol of hydrogen gas occupy at STP

1) 2.5 mol hydrogen gas = 22.4 L/ 1 mol = 556 L

litres to mols

2) 11.6 L = 1 mol/ 22.4 L = 0.518 mol

Example:

At STP a sample of oxygen gas contains 11.5 mol.
How many litres of oxygen gas are there?

11.5 mol = 22.4 L/ 1 mol = 258 L

150ml x 1 L/ 1000 ml = 0.15 L

0.15 L x 1 mol/ 22.4 L = 0.00670 mol

Extra Notes:
-In conversions mols will almost always equal 1
-Remember to convert values to the appropriate units when asked for a different unit
-Also remember to use significant figures because these are very important in conversions

Molar Mass Mass of Atoms

 Molar Mass
-The mass ( in grams ) of 1 mole of a substance is called the molar mass
- It can be determined from the atomic mass on the periodic table
- Measured in g/mol

Molar Mass of Compounds

- To determine the molar mass of a compound add the mass of all atoms together

Example

Element                  Molar Mass              *Significant Digits

H2O                   2 + 16 = 18.0g/mol  
NO2                  14 + 32 = 46.0g/mol
NaCl                  23 + 35.5 = 58.5g/mol  
FeO                   55.8 + 16 = 71.8g/mol
NaNO3             23 + 14 + 48 = 85.0g/mol

 Converting between moles and mass
- To convert between moles and mass we use molar mass as the conversion factor
- Be sure to cancel the appropriate units

Examples

How may grams is there in 1.5 mol of O2?


1.5mol O2 x 32.0g   = 48g
                  1 mol O2


Example

A sample of HCl contains .54 mol. How many grams of HCl is this?

.54mol HCl x 36.5g     = 20g HCl
                    1 mol HCl


Example

A compound is made of phosphorus and chlorine. It is found to contain 0.200 mol and has a mass of 27.5g
- Determine the molar mass of the compound
- Suggest a possible formula

0.200mol x 27.5g  =  137.5g/mol            Formula = PCl3
                        1 mol

Naming Compounds

Chemical Nomenclature

-Today, the most common system is IUPAC for most elements like,

1. Ions
2. Binary Ionic
3. Polyatomic Ions
4. Molecular Compounds
5. Hydrates
6. Acids/Bases

Chemical Formulas

-Beware of the differences between Ion and Compound Formulas

Eg.


Zn^2+ (The 2+ means an Ion Charge)
BaCl2   (The 2 means the number of Ions)

Multivalent Ions

-Some elements can form more than one ion.
  -Eg. Iron > Fe^3+ or Fe^2+
  -Eg. Copper > Cu^2+ or Cu^1+
-The top number on the P.T. (Periodic Table) is more common
-IUPAC was uses roman numerals in parenthesis to show the charge
-Classical (i.e. Old) systems uses latin names of elements and the suffixes like '-ic' (larger charge) and '-ous' (smaller charge)
  -Eg. Ferric Oxide
            /\
      Refers to Iron (Fe)
      '-ic' refers to larger charge
      So iron's charge would be +3 not +2

Other Classical Names
-Ferr - Iron
-Cupp - Copper
-Mercur - Mercury
-Stann - Tin
-Aunn - Gold
-Plumb - Lead

Eg.  FeCl2 - Ferrous Chloride
       SnO2 - Stannic Oxide
       Pb(NO3)2 - Plumbous Nitrate

Hydrates

-Some compounds can form lattice that bond to water molecules

   -Copper Sulfate
   -Sodium Sulfate                                   Without water, the compounds is often preceeded by 'anhydrous'


-These crystals contain water inside them which can be released by heating
-To name hydrates

1. Write the name of the chemical formula
2. Add a prefix indicating the number of water molecules (mono, di, tri, tetra, penta etc..)
3. Add hydrate after the prefix

Eg. Li(ClO4) 3H2O - Lithium Perchlorate Trihydrate

Molecular Compounds

-Write names of the following compounds

N2O4 - Dinitrate Tetraoxide

Naming Acids/Bases

-Hydrogen compounds are acids
   HCl > Hydrochloric acid

Naming Bases

-Caution and OH
   -NaOH - Sodium Hydroxide

Trends on the Periodic Table

-Elements close to each other on the periodic table display similar characteristics
-There are 7 important periodic trends
1. Reactivity
2. Ion charge
3. Melting point
4. Atomic Radius
5. Ionization energy
6. Electronegativity
7. Density*

Reactivity

-Metals and non-metals show different trends

-Te most reactive metal is Francium; the most reactive non-metal is Fluorine

Ion charge

-Elements ion charges depend on their group (column)

Heres a picture of the Ionic charges:http://www.chemprofessor.com/ptable4.gif

Melting point

-Elements in the center of the table of the highest melting point

-Noble gases have the lowest melting points

-Starting from the left and moving right, melting point increases (until the middle of the table)

Atomic Radius

-Radius decrease to the up and the right

-Helium has the smallest atomic radius

-Francium has the largest atomic radius

Ionization Energy

-Ionization energy is the energy needed to completely remove an election from an atom

-It increases going up and to the right

-All noble gases have high ionization energy

-Helium has the highest ionization energy

-Francium has the lowest ionization energy

-Opposite trend from atomic radius

Electronegativity

-Electronegativity refers to how much atoms want to gain electrons

-Same trend as ionization energy

Electronic Structure

Drawing Electron Dot Diagrams

-The nucleus is represented by the atomic symbol. 

- For individual elements determine the number of valence electrons.

- Electrons are represented by dots around the symbol.

- 4 orbitals (one of each side of the nucleus).

each holding a maximum of 2e. 

Lewis Diagrams for Compounds & Ions

- In compounds electrons are shared

1. Determine the # of valence e- for each atom.

2. Place atoms so that valence e- are shared to fill each orbital.

Double and Triple Bonds

- Sometimes the only way covalent compounds can fill all their valence levels is if they share more than one electron.

Ionic Compounds

- In ionic compounds electrons transfer from one element to another.

- Cation (metal - positive charge)

- Anion (non-metals - negative charge) 

Lewis Diagrams for Polyatomic Ions

1. Determine the # of valence e- for each atom in the molecule.

2. Subtract one electron for each positive charge.

3. Add one electron for each negative charge. 

Links:

The link giving step by step instructions on how to draw an electron dot diagram (shown in class)

1. http://www.youtube.com/watch?v=y6QZRBIO0-o

more info on Lewis structures of atoms, ions, and compounds.

2. http://www.ausetute.com.au/lewisstr.html

Jomar Delos Santos