This is in response to the fact that my experiment had me come up with my own.. I was supposed to measure out as close to 1g as possible of sodium bicarbonate as possible.. This is my lab procedures:
Plastic Cup A
1. Measure out 50 mL of distilled water with a 100-mL graduated cylinder. Transfer water to a plastic cup A and
place a coffee stirrer inside the cup.
2. Do not use the tare function to exclude the mass of a plastic cup and a stirrer. Place the mass of the plastic cup A
with water and a coffee stirrer inside on the balance. Measure the mass of the cup, water, and the stirrer together.
3. Place a weighing dish (use a cup cake paper) on the balance and press “tare”. Measure 1.00 g of sodium
bicarbonate as closely as you can. Record the mass of sodium bicarbonate you measure.
4. Transfer sodium bicarbonate to the plastic cup A.
5. Place a weighing dish (use a cup cake paper) on the balance and press “tare”. Measure 0.76 g of citric acid
as closely as you can. Record the mass of citric acid you measure.
Steps 6 and 7 need to be performed as quickly as possible to avoid the evaporation of water.
6. Transfer citric acid to the plastic cup A. Immediately you will see bubbles of carbon dioxide generated. Stir the
solution without spilling out the solution until all visible bubbles disappear.
7. Place the cup with the solution and the stirrer on the balance. Do not use the tare function to exclude the mass
of the cup and the stirrer. Measure the mass of the cup, the solution, and the stirrer together.
Now, For Cup A I had :
Mass of cup water & stirrer: 54.66
mass of sodium bicarbonate: 1.02g
mass of citric acid: .77g
total mass of all: 56.45
mass of cup, solution, stir after reaction: 56.21
difference (CO2 mass) = 0.24g
But my questions for post lab ask me :
The reaction of citric acid and sodium bicarbonate is written as
H3C6H5O7(aq) + 3 NaHCO3(aq) → Na3C6H5O7(aq) + 3 H2O(l) + 3 CO2(g)
Part A: Equivalence Amounts
Plastic Cup A
1. Show that the equivalence amount of citric acid for 1.00 g of sodium
bicarbonate is 0.76 g.
** this is where I just used the numbers it gave me! instead of plugging in my exact numbers of 1.02 g sodium bicarbonate and 0.77g of citric acid.. ?? Am I supposed to use my numbers? or just show the calculations of the equivalence?
2. Calculate the theoretical yield of carbon dioxide from 1.00 g of sodium bicarbonate.
How do I do this? and do I use 1.00g sodium or do I use the 1.02 g that I measured?
3. Calculate the percentage yield in the plastic cup A.
Is this where I use my exact numbers of my lab and calculate of plastic cup A? using 1.02g and 0.77 g? or should I have used those all along? I'm confused as to what to do now??
You did the 1 g NaHCO3 vs 0.76 g citric acid (as you posted earlier) correctly.
For #2 you use YOUR numbers.
mols in 1g NaHCO3 = 1.02/84 = about 0.012
Convert to mols CO2. That's approx 0.012 x 1 mol CO2/1 mol NaHCO3 = about 0.012 mols CO2.
Convert to grams CO2. 0.012 mol x 44 = 0.52. That's the theoretical yield. You measured 0.24 or about 46% yield
Great! Thanks again! I got it now! I can finish the rest of my lab from these questions... I have 4 cups to do ! lol
To answer your questions:
1. In order to show the equivalence amount of citric acid for 1.00 g of sodium bicarbonate, you should use the numbers provided in the lab procedures. The lab procedures state that you should measure 1.00 g of sodium bicarbonate and 0.76 g of citric acid. So, in this case, you would use those numbers to show the equivalence amount.
2. To calculate the theoretical yield of carbon dioxide from 1.00 g of sodium bicarbonate, you need to use the balanced chemical equation provided. According to the equation, 3 moles of carbon dioxide are produced for every moles of sodium bicarbonate. You would need to convert the mass of sodium bicarbonate to moles, and then use the mole ratio to calculate the moles of carbon dioxide. Finally, you can convert the moles of carbon dioxide to grams. As for which value to use, you should use the mass of sodium bicarbonate that you measured in your experiment, which is 1.02 g.
3. To calculate the percentage yield in plastic cup A, you need to compare the actual yield of carbon dioxide (which you calculated as 0.24 g, the difference in mass) to the theoretical yield (which you calculated in the previous step using the mass of sodium bicarbonate you measured). The percentage yield is calculated by dividing the actual yield by the theoretical yield, and then multiplying by 100. So, in this case, you would use the mass of sodium bicarbonate that you measured (1.02 g) and the actual yield of carbon dioxide (0.24 g) to calculate the percentage yield.