Mole to Mass and Mass to Mole

•  some questions will give you an amount of moles and ask you to determine the the mass. 
•  converting moles to mass only requires one additional step

                                        MOLES ------------- MOLES
                                             I                                  I
                                             I                                  I
                                             I                                  I
                                        MASS                         MASS

EXAMPLES:

--How many grams of (Al2O3) are required to produce 3.5 mol of pure aluminium.

1. Balance the equation                                          Al2O3 -->    Al  +     O2
                                                                         2  Al2O3 --> 4 Al  +  3   O2
2.Find the molar mass of (Al2O3) = 102g
3. Solve the problem                                  3.5mol Al x 2 Al2O3 x 102g  = 178.5g --> 1.8x 10 power of 2
                                                                                       4 Al        1 mol

-- How many grams of water are produced of 0.84 mol of (H3PO4) is completely neutralized barium hydroxide?

2H3PO4 + 3Ba(OH)2  --> 6H(OH) + Ba3 (PO4)2

0.84 mol x 6 x 1.8g  = 45.36g --> 45g
                 2   1mol
Nicole H

Classifying Chemical Reactions

Direct Combination Reaction: 2 or more reactants come together to form a single product
EX.  A + B ---> AB
        2Na + Cl2 ---->2NaCl
        S + O2 ---->SO2

Decomposition: a single compound is broken down into 2 or more smaller compounds or elements
EX.  AB ---> A + B
        2 H2O ----> 2H2 + O2
        CaCo3 ----> CaO + CO2

Single-Replacement: an uncombined element displaces an element that is part of a compound
EX.  A + Bx ---> Ax + B
         Mg + CuSO4 ----> MgSO4 + Cu
         Cl2 + 2KI ----> FeSO4 + Cu

Double-Replacement: atoms or ions from 2 different compounds replace eachother
EX.  Ax + By ----> Ay + Bx
        CaCO3 + 2HCl ----> CaCl2 + H2CO3

Janine R

Molecular Formulas

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

Example :
-- The empirical formula for the substance CH2O and its molar mass is 60.0 g/mol . Determine the molecular formula.

                                                        EMPIRICAL                      MOLECULAR
                                                             CH2O             x2                  C2H4O2
M.M.=12.0+2(1.0) +16.0
         = 30.0                                       30.0g/mol           x2                  60.0g/mol


*watch this video to help you solve empirical and molecular formulas*

http://www.youtube.com/watch?v=AFqwtY7m2PI

Nicole H

Empirical Formula

Empirical formula: are the simplest formula a compound
  - shows the simplest ratios, not the actual atoms

EXAMPLE:

 this is the difference between an empirical formula and a molecule formula

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

- to determine the ratio we use this table to help us solve the problem:

ATOM   MASS(g)    MOLAR MASS   MOLES             MOLE                        RATIO

                                                               (g/mol)       SMALLEST MOLE

please refer to this link on how to solve empirical probblems:

http://video.about.com/chemistry/Empirical-Formula.htm 

Nicole H

December 12-Density and Moles/Density of Gas

Density and Moles

These are the equations for density.
-density is measured in g/L or g/mL


EX.
How many moles are in 11.5mL of water? (H2O=18)

11.5g x 1mol = 0.639g<---don't forget about
             18 g                       significant digits




EX.
A small sample of silver contains 1.23x10(23) silver atoms. If the density is 10.5g/mL what is the volume of the silver sample?
-this is a multi-step conversion so you will have to go from atoms->moles->mass->density

1.23x10(23) atoms x      1mol      x 107.9g x 1mL = 2.1mL
                                 6.02x10(23)    1mol      10.5g

Density of Gas

-@STP we can find density by:
   mm                molar mass-->g/mol
22.4L/mol        molar volume-->L/mol

EX.
Determine the density of methane(CH4=16g) at STP.

16g
1mol  = 0.71g
22.4L
mol

Janine Roldan

December 3 - Moles of Iron and Copper Lab

Today we were assigned to do a lab. In this lab we had to determine the number of moles of copper produced in the reaction of iron and copper (ii) chloride, the number of moles of iron used up in the reaction of iron and copper (ii) chloride, the number of atoms and formula units involved in the reaction and, the ratio of moles or iron to moles of copper. 

This is our procedure:

• First of all we weighed a dry 250 mL to find its mass.
• Then we added about 8 grams of copper (II) chloride crystals into the beaker and weighed it.
• After, we added 50 mL of water to the beaker
• Then weighed the 2 nails and placed them into the copper (II) solution
• Then saw a formation happening to the nails and after a couple of minutes we carefully used tongs to pick up the nails and removed any of the remaining copper from it.
• After we dried the nails and removed the copper, we then weighed the nails again to find its new mass.
• The excess solution was poured into the beaker carefully through a funnel and filter paper.
• At last we placed the copper in a drying oven and then find the new mass of the beaker and the copper 

1. Janine Roldan

Multi-Step Conversion Review