stoichiometry

During the end of November, 2014, I reviewed five types of chemical reactions and predicting the products: Synthesis on 11/14/2014; Decomposition on 11/17/2014; Single Replacement on 11/21/2014; Double Replacement on 11/23/2014; and, Combustion of a Hydrocarbon on 11/25/2014.

With this information and a balanced chemical reaction, you can calculate the theoretical (ideal) yield of a chemical reaction, perform the lab and compare it to an actual yield of product collected.

A useful explanation of “stoichiometry” is:
“Stoichiometry is a section of chemistry that involves using relationships between reactants and/or products in a chemical reaction to determine desired quantitative data. In Greek, stoikhein means element and metron means measure, so stoichiometry literally translated means the measure of elements. (http://chemwiki.ucdavis.edu/Analytical_Chemistry/Chemical_Reactions/Stoichiometry_and_Balancing_Reactions )

Stoichiometry can be approached a few different ways – I find that using Dimensional+ Analysis or The Factor-Label Method (discussed on 09/02/2014) is a very clear way for students to work on these problems.

Here is a 16 minute video about Stoichiometry problems.  The beginning discussion of conversion factors is for the use of Dimensional Analysis in solving these problems:

I approach these problems with the same math, but focus on the problem left-to-right just because it’s the way we read English.  I like to write the mole ratio under each part of the chemical reaction.  For example,
 
                      2  Mg  +  1 O2  à  2 MgO

                           2      :     1      :     2  

I also point out that all of the conversion factors combine to form one big fraction.  For example,
 

3.00 g Mg      1 mol Mg        1 mol O2      32 g O2  
-------------------------------------------------------------------   =  1.98 g O2
                       24.3 g Mg       2 mol Mg     1 mol O2


Here are some worksheets using the skills of balancing equations and stoichiometry:


This worksheet only has two problems, but it could be projected for classroom lecture use:

http://woodridge.k12.oh.us/ourpages/users/dweaver/Chemistry/PracticeWorksheets/ReactionWorksheets/StoichiometryWorksheet1.pdf

 
The page contains an overview of the skills required for stoichiometry and answers:

http://academic.evergreen.edu/curricular/matterandmotion/chem_phys%5Cpractice_problems.htm

 
This worksheet with answers focuses on gas stoichiometry problems:

http://wolgemuthe.psd401.net/chemistry/09%20-%20pvt/documents/Gas_Stoichiometry%20Practice%201.pdf

 
This post contains several pages and answers related to stoichiometry:

http://chemislife.weebly.com/uploads/9/6/2/7/9627863/stoichiometry_worksheet.pdf

 
This posting is a good resource of stoichiometry questions and answers:

http://plaza.ufl.edu/ctoyota/worksheet%2013cgt.pdf

 
Check out the Topic List to help you to find past Blog entries.  I hope it helps!
 
The holidays approach, so buy my lab book "Chemistry on a Budget" (or ask for it as a gift) -- it is available for $20 at amazon.com or $23 at lulu.com. It will take a few weeks to get to you, so order now!

http://www.amazon.com/Chemistry-Budget-Marjorie-R-Heesemann/dp/0578129159/ref=sr_1_1?s=books&ie=UTF8&qid=1389410170&sr=1-1&keywords=chemistry+on+a+budget

http://www.lulu.com/shop/marjorie-r-heesemann/chemistry-on-a-budget/paperback/product-21217600.html

“Chemistry on a Budget” includes the lab A Chemical Reaction that focuses on the stoichiometry of a simple reaction that provides very good results!

This book contains 13 labs using consumable materials purchased from local stores.  There are two versions of each lab, one with a ten-question conclusion and one with directions for a full lab report.  This way the teacher has the option!  Each lab is two pages to allow for one two-sided handout.

Have a great weekend!