[learner101]

Hi guys,
I have an assessment soon and I'm having trouble with some past question. If someone could help please.

A vitamin and mineral beverage sample containing an unknown concentration of Ca2+ (aq) gave an absorbance of 0.2 in atomiic absorptiion. "Spiking" the beverage sample with aliquots of Ca2+ (aq) led to the data plotted with a solid line in a graph. the second, dotted trace was obtained by adding equivalent amounts of Ca2+ (aq) to deionised water instead.

a) Suggest why the gradients of the two plots may differ
b) What concenration of Ca2+ (aq) would be determined for the beverage sample using the regular (dotted) calibration line for Ca2+ (aq) in deionised water?
c) Use the absorbance data for the spiked beverage samples to estimate the Ca2+ (aq) concentration.
d) What name is given to the approach taken in part (c), and under what circumstances should it be used?

[learner101]

Also,

I have a few more questions. Should I post them in this thread or  new ones?

[Arkcon]

Lets work together to begin to solve this one, and see how further questions on this topic goes.  Questions on a totally different topic should go in their own thread ... but ... don't expect us to do all you work for you (and yes, you have asked us to do all you work for you, this question, itself, asks 5 separate questions.)  We like to give hints, to help you understand for yourself.

OK.  Part a, that is a pretty advanced topic, we'll see what insights we can get.  Can you use the chart to answer b. and c.?  The two questions in part d are a definition.  We can't help you with a definition, you can look it up in a reference, like your textbook, class notes, or maybe an online search.

[learner101]

Hi,

Thanks for the reply

I don't understand the question at all and that is why I posted it. I don't expect a straight up answer. I just want an explanation as to how to go about this question.

 

[Arkcon]

Use the chart, as if it was a reference:  The uninspired sample gives an absorbance of 0.2, what concentration added to deionized water gives the same absorbance?

[learner101]

Use the chart, as if it was a reference:  The uninspired sample gives an absorbance of 0.2, what concentration added to deionized water gives the same absorbance?

0.1?