Question

If 26.223 mL of potassium permanganate solution is required to titrate 1.041 g of ferrous ammonium sulfate hexahydrate, { FeSO4(NH4)2So46H2O }, calculate the molarity of the KMno4 solution.

and the equation the lab gave me was

Mn04(-) + 8H(+) + 5Fe(+2) ----> Mn(2+) + 4H2O + 5 Fe(+3)

Answer 1

1. calculate the molecular mass of the ferrous salt. RMM

2. calculate the number of moles of ferrous salt. 1.041/RMM

3. from the equation 1 mole of permanganate reacts with five moles of the ferrous salt, hence the number of moles of permanganate is 1/5 of the number of moles of ferrous salt.

4. 26.223 ml is 0.026223 L. So the molarity of the permanganate solution is the number of moles from step 3 divided by 0.026223 L.

Does this make sense?

Answer 2

Yes but I come up like this
MW Fe = 55.845 divided by 342.0 = 0.16329 Moles of Fe

If 1 mole of KMnO4 is used for 5 Moles of Fe then Moles of KMnO4 = .03268 M

Molarity = Moles/Liter
Moles of KMnO4 = .03268 Moles
and 26.223 mL / 1000mL/Liter = .02633 L


Then answer should be around 1.241


55.845 / 342.0 =0.16329 moles Fe
/5 = .03268

/ .026223 = 1.245 M/L =1.245 M

Answer 3

Why 55.845/342?

1. I get the RMM to be 392 g mol-1 (please check my maths!)

So step 2. is

1.041g/392 g mol-1 = moles

which gives you the number of moles of Fe in the starting mass of the salt.

Now go from here....

Answer 4

That is what I get too.

But after dividing the concentration by 5 I get an answer of 1.245M

The answer is wrong! Or the teacher gave us the wrong answer.....

Answer 5

I was wondering if you (we) got the answer correct - I figure the RMM of the FASH to be to be 392g,mole .... so the 1.041g/392g/mole = number of moles. Then the number of moles of KMnO4 is 1/5 of that and then the rest is easy.
Number of moles of Fe = 55.845 / 392 = .142461734 Moles Fe
Number of moles of KMnO4 is .142461734 / 5 moles of Fe per mole KMnO4 = .028492346 Moles KMnO4
Molarity of solution is Moles/liter = .028492346 moles KMnO4 / .026223 liters KMnO4 = 1.09 Molar

Answer 6

I was wondering if you (we) got the answer correct - I figure the RMM of the FASH to be to be 392g,mole .... so the 1.041g/392g/mole = number of moles. Then the number of moles of KMnO4 is 1/5 of that and then the rest is easy.
Number of moles of Fe = 55.845 / 392 = .142461734 Moles Fe
Number of moles of KMnO4 is .142461734 / 5 moles of Fe per mole KMnO4 = .028492346 Moles KMnO4
Molarity of solution is Moles/liter = .028492346 moles KMnO4 / .026223 liters KMnO4 = 1.09 Molar maybe. LOL KUS UMAK IL MITNAKAH