September 25: Biodiesel and Stoichiometry Lab

Biodiesel and Stoichiometry Lab

Today, we conduced another lab about finding the percentage yield of biodiesel in the lab "Biodiesel and Stoichiometry Lab", in Section 1.31.

Equation used: Glycende (veg. oil) + 3CH3OH = Biodiesel + Glycerol

Purpose of Lab: Students will learn about the process of creating biodiesel. Biodiesel is created from fat or oil. This fat or oil can sometimes be feedstock fat or oil. It is reacted with an alcohol, in our case methanol, with a catalyst (sodium hydroxide).  Biodiesel can be used to as fuel for cars. Also the Glycerol can be used to create soap. 

Today in class most students did all two steps in the lab. First was the reaction, second was the separation. 

Procedure Part 1: 

1. Measure out 25 (we halved the amounts) ml of methanol (3CH3OH).
2. Weight 1.12 grams of KOH (catalyst).
3. Combine methanol and KOH, stir until the KOH dissolves. You know have potassium methoxide.
4. Measure out 125 ml of vegetable oil and add to methodixe mixture. 
5. Heat mixture to in-between 55-60 Celsius. Stir on plate, however, keep it constantly around 55-60 Celsius. Do this for around 45 minutes. 
6. After 45 minutes pour into separation funnel and let it sit for 10-15 minutes. 

Procedure Part 2: 

1. Slowly drain the bottom layer into a small beaker. This is the layer of glycerol. When all glycerol is done stop the plug. 
2. Drain the rest of the biodiesel and measure the mass. 

Measuring the masses of the starting materials: 

1. Mass = Density x Volume
2. Mass of KOH  
1. 1.11 (±) 0.1 g
3. Mass of methanol  (3CH3OH) 
1. 0.79 (density) x 25 (volume) = 19.75 g
4. Mass of oil 
1.  0.9 (density) x 125 (volume) = 112.5 g

Finding the Limiting Reactant: 

1. Mole of the Oil is .127 g 
1. mass/ molar mass = mole
2. 112.5/ 885.4 (given) 
3. .127 
2. Mole of 3CH3OH is .616
1. Mass/ molar mass = mole
2. 19.75/ 32.05
3. .616
3. The ratio is 1:3 
1. times .127 by 3 you get .39 
2. You have more then .39 mole of 3CH3OH 
3. So 3CH3OH is in excess and the oil is the limiting factor 

Finding the theoretical yield of the biodiesel:

1. How much of the product will be created in ideal conditions
2. Multiply the amount of moles of the limiting reagent by the ration of the limiting regent 
1. .127  x 3 
2. .39
3. Multiple that by the molar mass.
1. 0.39  = mass/ 292 
1. 292 is the molar mass of the biodiesel 
2. theoretical yield= 113.8

Finding the actual yield of biodiesel:

1. How much of the product will be created 
2. 104.85 g 
1. Difference from others is we spilled some of our biodiesel so we will have less. 

Finding the Percentage Yield: 

Actual Yield/Theoretical Yield x 100 = Percentage Yield

104.85/113.8 x 100 = 92.13%

Homework: Finish lab and other questions. Quiz next class about topic 1.2.