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