# Basic Stoichiometry Phet Lab

Pages: 8 (1190 words) Published: April 30, 2013
Basic Stoichiometry PhET Lab rvsd 2/2011
Let's make some sandviches!
_
Introduction:
When we bake/cook something, we use a specific amount of each ingredient. Imagine if you made a batch of cookies and used way too many eggs, or not enough sugar. YUCK! In chemistry, reactions proceed with very specific recipes. The study of these recipes is stoichiometry. When the reactants are present in the correct amounts, the reaction will produce products. What happens if there are more or less of some of the reactants present?

Procedure: Load the "Reactants, Products, and Leftovers" simulation by going to http://phet.colorado.edu/ or googling "phet." You may have to download or update the version of Java on your computer. Complete each exercise on your own. Remember to use proper units and labels. PhET Simulations _ Play with the Sims _ Chemistry _ Reactants, Products, and Leftovers_ If a yellow bar drops down in your browser, click on it and select "Allow Blocked Content"

Part 1: Making Sandviches: _
The _ is a simulation of a two-reactant synthesis reaction. In this case, one reactant will be limiting, while the other will be in excess. Take some time and familiarize yourself with the simulation. Set the reaction to a simple mole ratio of 2:1:1_

Complete the table below while making tasty cheese sandwiches: Bread Used
Cheese Used
Excess Cheese

5 slices
5 slices
2 sandwiches
1 slice
3 slices

4 slices
3slices
2 sandwiches
0 slices
1 slice

5 slices
2 slices
2 sandwiches
1 slice
0 slices

6 slices
7 slices
3 sandwiches
0 slices
4 slices

Part 2: Real Chemical Reactions: _
_Now let's work with real chemical reaction, one that creates a very entertaining BOOM! What is the mole ratio for the reaction of hydrogen and oxygen to produce water? The mole ratio is 2 to1 to 1_ Complete the table below while making water H2O from hydrogen H2 and oxygen O2: Hydrogen Molecules H2

Oxygen Molecules O2
Water Molecules H2O
Excess H2
Excess O2

4 molecules
4 molecules
2 molecules
0 molecules
2 molecules

7 molecules
6 molecules
3 molecules
1 molecule
3 molecules

8 molecules
4 molecules
4 molecules
0 molecules
0 molecules

9 moles
8 moles
4.5 moles
0 moles
3.5 moles

9 moles
4 moles
4 moles
1 moles
0 moles

4.0 moles
2.5 moles
2 moles
0 moles
.5 moles

1.5 moles
.75 moles
1.5 moles
0 moles
0 moles

_Notice that the labels changed from molecules to moles. This does not change the mole ratio, as a mole is simply a large number of molecules. How many molecules is a mole?6.023 x 10^23 _________________

Now try producing ammonia, a very important chemical in industry and farming. What is the mole ratio for the production of ammonia? Ratio is 1:3:1_ Complete the table below:
Moles N2
Moles H2
Moles NH3
Excess N2
Excess H2

3 moles
6 moles
2 moles
1 mole
0 moles

6 moles
3 moles
1 mole
5 moles
0 moles

4 moles
12 moles
4 moles
2 moles
0 moles

1.5 moles
4.0 moles
1 mole
.5 moles
1 mole

Combustion of hydrocarbons like methane CH4 produce two products, water and carbon dioxide CO2. What is the mole ratio for the combustion of methane? Ratio is 1:2_ Complete the table below: WATCH FOR FRACTIONS

mol CH4
mol O2
mol CO2
mol H2O
Excess mol CH4
Excess mol O2

4 mol
4 mol
2 mol
4 mol
2 mol
0 mol

3 mol
6 mol
3 mol
6 mol
0 mol
0 mol

2 mol
4 mol
2 mol
4 mol
0 mol
0 mol

3 mol
6 mol
3 mol
6 mol
0 mol
0 mol

The BEST PART: _.

Basic Stoichiometry Post-Lab Exercises rvsd 2/2011

Vocabulary:Before your begin, please define the following. The following site has a good chemistry glossary - http://antoine.frostburg.edu/chem/senese/101/index.shtml

Limiting Reactant:The reactant that limits the amount of product produced in a chemical reaction. Excess Reactant:...