[confus3d]

Can you guys help me check my answer? I don't know if I did it right =/

Pb+ was obtainable from the water-soluble salt lead (II) nitrate (Pb(NO₃)₂), which the student decided to make by the following reaction. (The desired product was to be isolated by the slow evaporation of the water).

PbO (s) + 2HNO₃ (aq) → Pb(NO₃)₂ (aq) + H₂O (l)

Losses of product for various reasons were expected, but a yield of 86.0% was expected. In order to have 5.00 grams of product at this yield, how many grams of PbO should be used? (Assume that sufficient nitric acid would be used.)
I got 3.92 g of PbO

2. The potassium salt of benzoic acid, potassium benzoate (KC7H5O2), can be made by the action of potassium permanganate (KMnO4) on toluene (C7H8) as follows:

C₇H₈ + 2KMnO₄ → KC₇H₅O₂ + 2MnO₂ + KOH + H₂O

If the yield of potassium benzoate cannot realistically be expected to yield more than 71%, what is the minimum number of grams of toluene needed to achieve this yield while producing 11.5 grams of potassium benzoate?
I got 9.32 g C₇H₈

3. Based solely on the amount of carbon available, how many grams of sodium oxalate (Na₂C₂O₄) could be obtained from 125 grams of C₆H₆? (Assume that no loss of carbon occurs.)
This one I don't really understand at ALL

4. Aluminum sulfate (Al₂(SO⁴)₃) can be made by the following reaction:

2AlCl₃ (aq) + 3H₂SO₄ (aq) → Al₂(SO₄)₃ (aq) + 6HCl (aq)

It is quite soluble in water, so to isolate it the solution has to be evaporated to dryness. This process drives off the volatile HCl, but the residual solid has to be heated to a little over 200 C to drive off all the water. Two experiments were conducted, and each used 25.00 grams of AlCl₃.

In the first experiment, 50.00 grams of H₂SO₄ was used. Which of the reactants is limiting?
H₂SO₄
In the second experiment, the amount of H₂SO₄ was in perfect stoichiometric ratio with the AlCl3. There was eventually isolated 28.36 grams of pure Al₂(SO₄)₃. Calculate the percent yield.
88.4%

[Yggdrasil]

1. correct
2. correct
3. how many moles of carbon are in 125g of benzene?  how many grams of sodium oxalate contain that amount of carbon?
4. a. I get that the aluminum chloride is limmiting.  If you show your work maybe I can see where the error is.
b.  correct

[confus3d]

for 4a. I did
2/3 = x/50g
x= 33.33 g
You'd need 33.33 g of AlCl3
And since I need 33.33g but I have 25.00 g of AlCl3, then isn't the H2SO4 limiting?

For number 3, how would you determine the moles of just carbon?
I don't know if this is right but I did..
125 g C6H6 X 1 mol/ 78 g= 1.60 mol C6H6 = 1 mol C6
bc I think I read yesterday that one mol of a formula = one mol of what it's made of? I forgot but is that right? or not at all?

[Yggdrasil]

The 2/3 is a ratio of moles not mass.  You first need to find out how many moles of sulfuric acid and aluminum chloride you have and then use the ratios from the balanced chemical reaction.

For number three, the subscript 6 in C₆H₆ means that each molecule of benzene contains six atoms of carbon.  Therefore, one mole of benzene contains six moles of carbon atoms.