Homework Help: Chemistry

Posted by Bailey on Wednesday, November 7, 2012 at 4:21pm.

I am stuggling with my chemistry experiment.
I am given thr following:
The reaction of citric acid and sodium bicarbonate is written as
H3C6H5O7(aq) + 3NaHCO3(aq) --> Na3C6H5O7(aq) + 3H2O(l) + 3CO2(g)

1.) Mass of cup A, water, and stirrer = 54.3 g
2.) Mass of sodium bicarbonate = 1.00g
3.) Mass of citric acid = .76g
4.) Total Mass = 56.06g
5.) Total Mass after reaction= 55.63g
6.) Differnece 0.43g

I'm asked to calculate the theoretical yield of carbon dioxide from 1.00g of sodium bicarbonate. And to calculate the precentage yield in the plastic cup A.

I am totally lost and don't know how to even begin to set up equations to solve. Any help appreciated.

Chemistry - DrBob222, Wednesday, November 7, 2012 at 7:01pm
Several problems, including a limiting reagent problem, all rolled into one.
mol NaHCO3 = grams/molar mass = ?
mols citric acid = g/molar mass = ?

Convert mols NaHCO3 to mols CO2 using the coefficients in the balanced equation.
That's ?mol NaHCO3 x (3 mols CO2/3 mols NaHCO3) = ? mol NaHCO3 x 1/1 = ?mol CO2.

Do the same with citric acid.
? mols citric acid x (3 mols CO2/1 mol H3C6H5O7) = ?mols citric acid x 3 = ?

It is likely that these two values for mols CO2 will not agree which means one of them is wrong. The correct value in limiting reagent problems is ALWAYS the smaller value and the reagent producing that value is the limiting reagent. Then smaller value mols CO2 x molar mass CO2 = grams CO2. This is theoretical yield (TY).
The actual yield (AY) in the problem is 0.43 g CO2.
%yield = (AY/TY)*100 = ?
Chemistry - Bailey, Wednesday, November 7, 2012 at 7:43pm
Am I doing this right?
mol NaHCO3 = grams/molar mass = 1/85 = 0.0117647059*3=0.0352941176
mols citric acid = g/molar mass = 1/316 = .003164557*3=0.009493671
So, the second one is correct and is the limiting reactant.
0.009493671 mols CO2 x 44 CO2 = 0.417721524 = .42 grams CO2. This is theoretical yield (TY).
The actual yield (AY) in the problem is 0.43 g CO2.
%yield = (0.43/0.42)*100 = 102.3809524 = 102%

is any of this right?
Chemistry - DrBob222, Wednesday, November 7, 2012 at 10:03pm
The procedure is right because you're following my directions; however, your numbers are wrong.
1. The molar mass NaHCO3 is not 85.
2. The molar mass citric acid is not 316.
3. The mass citric acid is not 1 g (from the problem.

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