Stainless steel is a corrosion resistant alloy composed of nickel, chromium and iron. A lab technician was assigned to determine the mass of chromium in a 2.50 g sample of stainless steel. The sample was first dissolved in acid to convert the chromium metal in the sample into chromium (II) ions. The acidified chromium (II) ions were then titrated with 17.69 mL of 0.125 mol/L perchlorate solution according to the unbalanced equation: ClO4- +Cr2+ -- Cl- + Cr 3+ Calculate the mass of chromium found in the 2.50 g sample of stainless steel.

Question

Stainless steel is a corrosion resistant alloy composed of nickel, chromium and iron. A lab technician was assigned to determine the mass of chromium in a 2.50 g sample of stainless steel. The sample was first dissolved in acid to convert the chromium metal in the sample into chromium (II) ions. The acidified chromium (II) ions were then titrated with 17.69 mL of 0.125 mol/L perchlorate solution according to the unbalanced equation: ClO4- +Cr2+ --> Cl- + Cr 3+ Calculate the mass of chromium found in the 2.50 g sample of stainless steel.

myininaya · Answer

Is there an equation to use?

myininaya · Answer

a mathematical one

anonymous · Answer

yes

myininaya · Answer

do we need to balance the chemical equation first?

myininaya · Answer

wait i don't see how

anonymous · Answer

i think so.. half reactions?

myininaya · Answer

there are no O on the other side

anonymous · Answer

oxidation and reduction half reactions (redox)

myininaya · Answer

was trying to find an example

myininaya · Answer

i think this is definitely beyond my chemistry understanding
i'm sorry i cannot help

anonymous · Answer

it's okay... thanks for trying ! :)

anonymous · Answer

Do you know anyone who is good at chemistry?

myininaya · Answer

http://www.wolframalpha.com/input/?i=balance+ClO4-+%2BCr2%2B+--%3E+Cl-+%2B+Cr+3%2B I don't know if this helps... But it says the molar mass in chromuim(II) is 51.9961 g/mol and chromuim(III) is 51.9961 g/mol

myininaya · Answer

I don't know if molar mass is different during regular mass
or what the relationship is
or how they got those numbers
but maybe somehow you can use it to check any work you have done so far

myininaya · Answer

and for some reason it couldn't balance it

anonymous · Answer

I think you need to separate them into half reactions by using "table of selected Standard Electrode Potentials"

anonymous · Answer

than balancing the electrons and put them in a net equation...

myininaya · Answer

I have to read up on this. I will be back tomorrow.

myininaya · Answer

I sorta found an example but it is with balanced chemical equations

myininaya · Answer

http://wps.prenhall.com/wps/media/objects/3311/3390507/blb0406.html So I'm going to read this...

myininaya · Answer

$$17.69 mL \cdot \frac{1 L}{1000 mL} \cdot ? \frac{mol Cr }{L}$$

myininaya · Answer

I don't know what that question mark should be though

myininaya · Answer

we are not given the mol/L thing for Cr

anonymous · Answer

molar ratio for the question mark

anonymous · Answer

I find this link... http://kcourses.weebly.com/uploads/1/6/8/1/16813808/2.5-redox_stoichometry.pdf

sweetburger · Answer

i think this is a redox titration involving some gravimetrical analyses

anonymous · Answer

yes, it is. im not sure how to approach it.

anonymous · Answer

I know that you need to make half reactions...

sweetburger · Answer

alright first determine the moles of percholorate  .01769L X  .125 mole/1L

anonymous · Answer

it is 0.00221125mol