Learning Materials
Features
Discover
Chapter 5: Q29P (page 117)
State when standard additions and internal standards, instead of a calibration curve, are desirable, and why.
The cause of desirability is described in the below steps
Over 30 million students worldwide already upgrade their learning with Vaia!
All the tools & learning materials you need for study success - in one app.
Get started for free
Standard addition graph. Students performed an experiment like that in Figure 5-7 in which each flask contained of serum, varying additions of standard, and a total volume of
(a) Prepare a standard addition graph and find in the serum.
(b) Find the standard deviation and confidence interval for .
Olympic athletes are tested to see if they are using illegal performance-enhancing drugs. Suppose that urine samples are taken and analyzed and the rate of false positive results is 1 %. Suppose also that it is too expensive to refine the method to reduce the rate of false positive results. We do not want to accuse innocent people of using illegal drugs. What can you do to reduce the rate of false accusations even though the test always has a false positive rate of 1 %?
5-28. Ititandard addition. Lead in dry river sediment was extracted with of filtered extract was mixed with other reagents to bring the total volume to was measured electrochemically with a series of standard additions of
(a) Volume is not constant, so follow the procedure of Figures 5-5 and 5-6 to find
extract.
(b) Find the standard uncertainty and confidence interval for the intercept of the graph. Assuming that uncertainty in intercept is larger than other uncertainties, estimate the uncertainty in ppm extract.
Why is it desirable in the method of standard addition to add a small volume of concentrated standard rather than a large volume of dilute standard?
Standard addition. An unknown sample of gave a current of in an electrochemical analysis. When of solution containing role="math" localid="1654761474124" was added to of unknown, the current increased to .
(a) Denoting the initial, unknown concentration as , write an expression for the final concentration, , after role="math" of unknown were mixed with of standard. Use the dilution factor for this calculation.
(b) In a similar manner, write the final concentration of added standard , designated as .
(c) Findin the unknown.
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Exams 
GCSE 
IGCSE 
AS 
A Level 
International A Level 
University Admissions Tests 
Flashcards 
Vaia AI 
Notes 
Study Plans 
Study Sets 
Find a job 
Find a degree 
Student Deals 
Magazine 
Mobile App