Mole to Mole Conversions

- Coefficients in balanced equations tell us the number of moles reacted or produced. 

- They can also be used as conversion factors.

Rule for conversion:

*WHAT YOU NEED OVER WHAT YOU HAVE

*Coefficients have to be in moles.

Example 1: 

A + 3B > 2C

6 mol      ? mol

6 mol B x 1A (what we need)= 2 mol of A

                 --------------------------  

                 3B (what we have)

Example 2:

A + 7 B > 9c

       -   

       2    

0.25 mol of A x 3.5 B  = 0.88 mol

                          ------

                          1A

Jomar Delos Santos

Stoichiometry Quantitative Chemistry

- Stoichiometry is a branch of chemistry that deals with the quantitative analysis of chemical reactions
- It is a generalization of mole conversions to chemical reactions
- Understanding 6 types of chemical reactions is the foundation of Stoichiometry

6 types of Reactions

1. Synthesis ( formation )
2. Decomposition
3. Single Replacement ( SR )
4. Double Replacement ( DR )
5. Neutralization
6. Combustion

Synthesis

- A+B ---> AB
- usually elements ---> Compounds

Decomposition

- AB ---> A+B
- Reverse of synthesis
- Always assume the compounds decompose into elements during decomposition

Single Replacement (SR)

- A+BC ---> B+AC

Double Replacement (DR)

- AB+CD ---> AD+BC

Neutralization

- Reaction between an acid and a base

Combustion

- Reactions of something (usually hydrocarbon) with air
- Hydrocarbon combustion always produces CO2 and H2O

MULTISTEP CONVERSIONS

Density->Mass - Use the formula d=m/v
Mass->Mole - Take the weight and multiply by 1mol/it's total molar mass
Mole->Mass - take the number of moles and multiply by STP (22.4L)
Mole->Molecules - Take the number of moles and multiply by avogadros number

Multistep Tutorial
http://www.schooltube.com/video/465930e6ab6bb972a1dc/Multiple-Step-Mole-Conversion-Tutorial



K.P

Empirical and Molecular Formulas

Empirical Formulas 

-Empirical formulas are the simplest formula of a compound 

-They show only the simplest ratios, not the actual number of atoms

-Molecular formulas give the actual number of atoms 

-To determine the empirical formula we need to know the ratio of each element 

Example: A sample of an unknown compound is found to contain 8.4 g of Carbon 2.1g of Hydrogen and 5.6g of Oxygen. Determine the empirical formula: 

Atom /     Mass/   Molar Mass/  Moles/  Mole - Smallest  Mole/ Ratio

C        /      8.4g/         12.0       / 0.7      /                 2                    /  2   >  C(2) 

H        /      2.1g/          1.0       /    2.1   /                  6                   /    6  >  H(6)

O        /      5.6g/         16.0      /    0.35 /                  1                    /    1 >  O (1)

C2 H6 O = Empirical Formula 

The simplest ratio may be decimals. For certain decimals you need to multiply by a certain number.

Decimal                 Multiplying Co-efficient

0.5                                         2

0.33 or 0.66                           3

0.25 or 0.75                           4 

0.2, 0.4, 0.6, 0.8                    5 

Molecular Formulas 

-If you know an empirical formula, to find the molecular formula you need the molar mass

Example: 

The empirical formula for a substance is CH2O

and its molar mass os 60.0g/mol. Determine the molecular formula 

Empirical               Molecular

CH2O  >>>x2>>>> C2H4O2

30.0 g/mol  >>>x2>> 60.0 g/mol

Jomar Delos Santos

               

LAB: Iron and and Copper Chloride

Problem: What is the ratio of moles of Copper formed to moles of Iron reacted in the chemical reaction described below?

To find the answer to this question our group placed an Iron nail in a solution of Cupric Chloride after measuring the filter paper and mass of the nail. We observed an immediate change in the color of the nail; it turned a rusty red. We learned that the iron was dissolving. These dissolved iron particles will combine to form Ferric Chloride. After, we removed the nail form the solution and dried it then we transfered the solution in to a separate beaker using filter paper. We measured the mass of the nail. It took a long time for the solution to filter. We determined the mass of Iron consumed  by comparing the mass of the nail before and after the reaction. After the solution had filtered we transferred the Ferric Chloride and the filter paper to dry in the drying oven. We have yet to measure its mass then we can determine the mass mass of the Ferric Chloride formed.

Group: Jennifer, Jomar, Paulette

Density and Moles

Density
-Density is a measure of mass per volume d = m
                                                                      V
-measured in g/L or g/mL

Example
-Water has a density of 1.0g/mL. Determine the mass of 11.5mL of water
-How many moles are in 11.5mL of water?

1.0g/mL x 11.5mL = 11.5g
11.5g x 1 mol = 0.64 mol
             18 g

Density of Gases

-The density of gases varies with temperature

-At STP we can find density by:  MM              molar mass               

                                               22.4L/mol        molar volume

Example
-Calculate the density of 02 STP

32.0g/mol = 1.43g/L
22.4L/mol

-An unknown diatomic gas has a density of 1.696g/mol STP
 -Find its molar mass
 -What is the chemical formula

1.696g/L x 22.4L/ 1 mol = 37.99g/mol = 38g/mol
                                                                  2
                                                            = 19g/mol
Chemical formula : F2

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