Synthesis of oxalate complexes, post lab question

[natash]

Homework Statement

Okay I'm having trouble with my post lab question. This lab is on the synthesis of Iron(III) Oxalates. I have to figure out the theoretical yield, but i can't seem to even find a balanced equation. I've gone over this a million times but can't seem to figure it out.

here is the procedure
1. a) prepare 10 g of ferrous ammonium sulfate dissolved in 30mL of water containing 2 drops of 6M H2SO4 b) 6g of oxalic acid in 50 mL of water c) 6.6 g of K2C2O4H2O in 18 mL of water d) 1.7 g oxalic acid in 15 mL of water

2. carry out the following preparation in a 250 mL beaker. To the ferrous ammonium sufate solution add, with stirring, the solution of 6 g oxalic acid in water. A yellow precipitate of iron(II) oxalate forms quickly. Carefully heat the mixture to near boiling, stirring constantly to avoid bumping. Allow the precipitate to settle, decant and discard the supernatant liquid.

3. wash the precipitate three times by adding 30mL of hot water, stirring and decanting the liquid. Filtering is not necessary at this stage of the synthesis.

4. add the 6.6g potassium oxalate/18mL water solution to the wet iron (II) oxalate precipitate and heat the mixture to about 50 C. Slowly add 17ml of 6% H2O2 while stirring and maintaining a temperature of about 50 C for at least 15 mins or until al the unconverted iron (II) oxalate is converted.

5. heat the mixture to boiling and slowly add the 1.7g oxalic acid in 15mL water solution ; maintain the temperature near boiling for 10 mins. filter away any precipitate before adding ethanol. Add 20 mL 95% ethanol t the filtrate. cover the beaker with a watchglass, wrap in aluminum foil and place the beaker in your locker until next week.

6.after 1 week, filter the green product crystals with a buchner funnel, and wash twice with a few mL of 50% aqueous ethanol, then with a few mL of 95% ethanol. Continue to aspirate the crystals on the filter for 30 mins. to air dry your samples. Cover with aluminum foil during drying to prevent photocomposition. when dry, isolate and weigh your sample to determine the % yield.

Homework Equations

%yield=actual yield/theoretical yeild *100 for actual yield i got 2.835g

The Attempt at a Solution

I'm not sure do I start out with 10g of ferrous ammonium sulfate and convert to moles to find theoretical yield...im so confused

 

[Borek]

What is formula of the complex you were preparing?

 

[Blueshift5]

I would first suggest going back to the lab procedure and carefully reviewing each step to ensure that you understand what is happening at each stage. It may also be helpful to consult with your lab instructor or classmates if you are still unsure.

To answer your question, yes, you would start with the 10g of ferrous ammonium sulfate and convert it to moles to find the theoretical yield. The balanced equation for the synthesis of iron(III) oxalate is:

Fe(NH4)2(SO4)2 + H2C2O4 + 2K2C2O4 + 2H2O2 → Fe(C2O4)3 + 2(NH4)2SO4 + 4KHSO4 + 2H2O

From this equation, you can see that for every 1 mole of ferrous ammonium sulfate, you should theoretically produce 1 mole of iron(III) oxalate. So, if you have 10g of ferrous ammonium sulfate, you can convert it to moles using its molar mass (you can find this in a periodic table), and then use the molar ratio from the balanced equation to determine the theoretical yield of iron(III) oxalate.

I would also suggest double-checking your calculations and making sure you are using the correct units throughout. It may also be helpful to compare your results with your classmates or the expected theoretical yield provided by your lab instructor. Good luck with your post lab question!