Calibration graph question...help

[Tonychet2]

question 13.....2012 tsfx chem practice exam

Many breakfast cereals are fortified with added vitamins and minerals. In one particular brand of bran flakes, extra iron is added. To determine the iron concentration in the bran flakes, 2.00g of the cereal was mixed with 20.0 ml of concentrated hydrochloric acid to liberate the iron. The solution was filtered and mae up to 50.0 ml using deionised water. 5.00 ml was then analysed using atomic absorption spectroscopy. An absorbance reading of 40.00 absorbance units was recorded for the sample/ A series of standard solution containing iron were then analysed under identical conditions to generate the calibration graph shown below.


concentration from reading graph = 2.67mg/L

A standard serving of bran flakes is considered to be 45.0g. How many milligrams of iron are in one standard serve?

A. 2.93mg
B. 0.130 mg
C. 14.6 mg
D. 0.59 mg

[bentennason]

2.67mg Fe -> 1000mL
x                -> 5mL

x= 0.00001335g Fe in 5mL

In 50mL, there is 0.0001335g Fe.
m(Fe) in 50mL= m(Fe) in 2g cereal

In 45g of cereal, m(Fe)= 3mg

Is that the right way to approach?

[Tonychet2]

yes that should be right... i cant believe i couldnt understand this question last night was so tired from overstudying i guess lol