How to solve my chemistry question?

Posted on 2015-08-18 11:33:00 in Chemistry by LYND

Question 1 

f a Fe stock solution has a concentration of 1.6 mg/mL, what is the concentration when 2 mL of this stock solution is diluted to 50. mL? Keep 2 sig figs for the answer. 



Question 2 



What is the absorbance if the % transmittance is 43%? Keep 2 sig figs for the answer. 



Question 3 



The Total Cereal has a Fe concentration of 0.6 g Fe per g of Cereal. However, it is very common for students to get less than 0.6. Which of the following can be contributors to this lower experimental result than the manufacturer listed value? There are three correct answers and find all of them. 



1-Under-digestion of cereal sample 



2-Complexing agent was occupied by excess amount of H+ and did not have a chance to complex with Fe 



3-Other materials from Cereal sample absorbs too much light 



4-The Fe was oxidized from 2+ ion to 3+ ion 



5-Some Fe was lost during a few transfers between glassware 



Question 4 



A=ebc, where A is absorbance, which is unit-less, b is path length that is 1 cm for the cuvette used. If the concentration c uses mol/L, what unit should the extinction coefficient e have? 



A-mol/L 



B-L/(mol*cm) 



C-(cm*L)/mol 



D-(cm*mol)/L

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