March 15th

Guess what guys? There are no stoichiometry calculations today! Instead, we are doing a lab!

A lab? I can hardly wait!

Lab 6D:

Determining the Limiting Reactant and Percent Yield in a Precipitation Reaction

In this lab, our main objectives are to observe the double replacement reaction of sodium carbonate and calcium chloride, to determine which reactant is the limiting one and which reactant is the excess one, and to obtain a theoretical mass and an actual mass, and then calculate the percent yield using the two pieces of information.

Phew! That was a mouthful!

In this lab, we need two 25mL graduated cylinders...

...and one 250mL beaker.

We'll fill one of the cylinders with a Na2CO3 solution, and the other one with a CaCl2 solution. Then we pour both of these solutions into the beaker and wait for five minutes while the solution sits.

Next, we take a piece of filter paper and put our group names on it with a pencil. We weigh the filter paper, then fold it into a fan and place it into a filter funnel. Finally, we pour the solution into the filter funnel, and then remove the wet filter paper filled with the CaCO3 precipitate. We put that on a paper towel in a safe place and wait for it to dry.

A new formula is introduced in this lab to calculate percent yield:

% Yield:

actual mass produced (in grams)           x     100%

theoretical mass produced (in grams)        

Now that we have our formula, we need our mole ratio. How do we obtain that? Simple! Using the word equation, we can write out a double replacement equation!

1 CaCl2(aq) + 1 Na2CO3(aq) ----> 

1 CaCO3(s) + 2 NaCl(aq)

 

 

Next time, we'll measure out the CaCO3 we have left, and we'll use the % yield formula to calculate the theoretical yield!