Density and Moles

Density:

- is a measure of mass per volume.
- is measured in g/mL or g/L
- Formula for density is
         

Example:

Oxygen has a density of 1.0 g/ml. Determine the mass of 11.5 mL of oxygen gas.

11.5 mL x 1.0 g      = 11.5 g
                  1 mL

How many moles are there in 11.5 mL of oxygen?

11.5 g x 1 mol   =  0.639 mol
                18 g


http://www.youtube.com/watch?v=REtBibhIqfo


Density of gases:

The density of gases can vary with the temperture.
If the temperature is at STP, we can find density by "

Molar Mass
22.4 L/mol

Example:

32g/mol       = 1.4 g/ L
22.4L/mol

-Candace Chan

Converting between Moles to Molecules to Atoms

In this conversion, A mole of any substance is 6.02×10²³ molecules of that substance.

To convert moles to atoms, you first convert the mole to molecules then use the element's subscripts and multiply it to the answer.

0.001 moles water ×

(

6.02×1023 water molecules 1 mole water

)

= 6.02×1020 water molecules

100 water molecules ×

(

1 mole water 6.02×1023 water molecules

)

= 1.66× 10-22 moles water

http://www.youtube.com/watch?v=21tLXgeYALc

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
• measure in grams over moles (g/mole)

Molar Mass of Compounds

• to determine the molar mass of a compound add the mass of all the atoms together

Element:

FeO- 55.8=16.0=71.8 g/mol

NO- 14=2(16)= 46.0 g/mol

PCl˅5- 31.0+5(35.5)= 208.5 g/mol

Na˅2SO˅4- 2(23.0)=32.1+4(16.0)= 142.1 g/mol 

H˅2O- 2(1.0)=16.0= 18.0 g/mol 

AlCl˅3- 27.0=3(35.5)= 133.5 g/mol

http://www.youtube.com/watch?v=ZqS38Il8--s

By: Krysta Del Rosario :D

Moles to Volume Conversion

At a specific pressure and temperature, one mole of any gas always have the same volume.
1) At 0 degree C and  101.3 kPa: 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 4.7 mol of O2 have at STP?

4.5 mol x  22.4 L  = 1.0 x 10^2 litres
                  1 mol




http://www.youtube.com/watch?v=AHqNiEwcXiE

- Candace Chan

Mole Conversions (Converting between grams and moles)

Converting between moles and mass(grams):
1) To convert the units, we use molar mass as the conversion factor. Molar mass is the number of atomic mass added together.
2) Be sure to cancel out the appropriate units.
* remember about the significant digits!
Examples:

How many grams are in 2.5 mol of Cl2?

2.5 mol x   71g      = 1.8 x 10^2 grams
                1 mol
           
How many moles are there in 205g of BeF2?

205g x   1 mol  = 4.36 mol
                47 g



http://www.youtube.com/watch?v=ehepBBtSbDc

-Candace Chan

Avogadro's Number- 6.02 x 10^23

• Atoms and molecules are extremely small
• Macroscopic objects contain too many to count or weight individually
• Amedeo Avogadro proposed that the only number of atoms in 12.00000g of Carbon be equal to a constant (= 1 mol of C)
• This value is now called Avogadro's number and forms the basis of all quantitative chemistry
• 1.0 mol= 6.02 x 10^22 atom
• 1 pair= 2
• 1 dozen= 12
• 1 century= 100
• 1 mol= 6.02 x 10^23
• One mole represents a huge number of particles

Particle

Atom- element- 6.02 x 10^23/1 mol

Molecule- covalent compound- 6.02 x 10^23/ 1 mol

Formula unit- ionic compound- 6.02 x 10^23/1 mol

Example: 2.47 x 10^25 atoms x 1 mol/ 6.02 x 10^23 atoms = 41 mol

http://www.youtube.com/watch?v=AsqEkF7hcII

By: Krysta Del Rosario :)

Hydrate Lab

  The purpose of this experiment is to determine the empirical formula of a hydrate.
               - Hydrates are ionic compounds that contain an inorganic salt compound loosely bound to water.

In this lab, we try to determine the anhydrous (without water) mass of the hydrate.

We had to determine the mass of water by boiling the substance over the bunsen burner and measure the test tube with the substance to find out how much water was in that substance.

We determuine the percent by using the formula:

% Error= measured - accepted    x 100
                       accepted

- Candace and Reo