[bloomfieldboss]

 

I'm trying to wrap my head around this one. 

Oxidation of Iodide to Iodine; Spectroscopic measurement of TriIodide ion.
IO3- + 5 I- + 6 H+ --> 3 H2O + 3 I2 (standard)
H2O2 + 2 I- + 2 H+ --> 2 H2O + I2 (unknown)
I- + I2 --> I3-


STANDARD: Put into a clean 250 mL volumetric flask exactly . 0.90 ml
of 1.00 mM iodate STANDARD.
Add an excess of 1M KI and 1M Sulfuric Acid and let stand for 5 minutes. Dilute to volume.

UNKNOWN: Pipet into a clean 250 mL volumetric flask 1.00 mL of your UNKNOWN and dilute to volume with distilled water.
Put into a clean 250 mL volumetric flask exactly . 0.90 mL
of this diluted H2O2 UNKNOWN.Add an excess of 1M KI and 1M Sulfuric Acid and let stand for 5 minutes. Dilute to volume (250 mL). Measure STANDARD and UNKNOWN spectroscopically at 360 nm using the same cuvet throughout.

% Transmission of BLANK.... 98.3 %
% Transmission of STANDARD..... 58.7 %
% Transmission of UNKNOWN... 51.7 %
(g) Absorbance of STANDARD.....… ___________________
(h) Absorbance of UNKNOWN...… ___________________
(i) Molarity of original UNKNOWN... ___________________ M


Okay I get the absorbance questions and how to do (i) but what Concentration do I use for C1 in the Beer's Law equation?? 

Side note -- When ever I ask my Chem teach a question he responds what's the problem?  Is this obvious am I missing something??

[Hunter2]

C1 is the amount of iodine optained from your standard. See equation.

[bloomfieldboss]

I realize that Hunter, I'm trying to figure out what Iodine's concentration is after diluting.  Thanks though.

[Hunter2]

The dilution is not the point. The 0.9 ml is your basic for standard and unknown probe.

[Arkcon]

Okay I get the absorbance questions and how to do (i) but what Concentration do I use for C1 in the Beer's Law equation?? 

Side note -- When ever I ask my Chem teach a question he responds what's the problem?  Is this obvious am I missing something??

Yes, I'm afraid you are missing something obvious, for this particular problem.  Let's try again.  Can you write out Beer's Law Equation, and underneath it, write in your known values in the correct position?  Let's see if it all comes together for you.