Empirical Formula, Limiting Reactant, and Percent Yield

Working through the analysis and conclusion questions, we are working to determine the empirical formula, limiting reactant, and percent yield for the experiment involving calcium chloride and sodium bicarbonate. 

HW: Complete the analysis and conclusion questions for the experiment.

Below are some hints to assist with your work:

Analysis:
1. You measured the mass of calcium chloride that I put into your baggie.  Use percent composition to determine the mass of calcium present in your baggie.

40.078g Ca
------------------
110.978g CaCl2

2. This is the mass of material in your filter.
3. This is the mass of material in your filter minus the mass of Ca in your bag.
4. Using answers from #1 and #3, convert grams Ca and CO3 to moles.
5. Divide larger number by the smaller number to get the mole ratio of Ca to CO3.

Conclusion:
4. The reaction is: CaCl2 + 2NaHCO3 -> CaCO3(s) + 2NaCl(aq) + H2O(l) + CO2(g)

6. What is the limiting reactant (all of the substance is used up in the reaction)?

• From your mass in grams, determine the number of moles of calcium chloride that you had in your baggie. 
• Now, looking at the reaction, how many moles of sodium bicarbonate react with one mole of calcium chloride? (2)
• Multiply your number of moles of calcium chloride by 2 to find the number of moles of sodium bicarbonate needed to react with all of your calcium chloride.
• Convert the number of moles of sodium bicarbonate to grams of sodium bicarbonate.
• Compare your calculated mass of sodium bicarbonate to your measured mass (from the lab) of sodium bicarbonate.  If your calculated mass is greater than your measured mass, then you did not have enough sodium bicarbonate to react with your calcium chloride (sodium bicarbonate is your limiting reactant).  If your calculated mass is less than your measured mass, then you had more than enough sodium bicarbonate to react with all of your calcium chloride (calcium chloride is your limiting reactant).

 7. What was the percent yield (actual mass of product/theoretical mass of product) from the experiment?

• Given a measured amount of your limiting reactant (assuming that it all reacted), you should be able to produce a certain amount of product.
• Convert the measured mass of your limiting reactant to moles.
• Now, looking at the reaction, how many moles of calcium carbonate are produced one mole of your limiting reactant?
• Using this ratio, convert the moles of limiting reactant to moles of calcium carbonate.
• Convert the moles of calcium carbonate to grams of calcium carbonate.  This is your theoretical mass of calcium carbonate.
• Calculate the % yield by

       actual measured mass of calcium carbonate

% yield = ------------------------------------------------------------ x 100

theoretical mass of calcium carbonate