The manganese concentration in a sample is determined using the Standard Additio

Question

The manganese concentration in a sample is determined using the Standard Additions method, with constant volume. The data is given below.

A plot of blank-corrected signal as a function of added [Mn] in ppm gives a best straight line with the equation y = 0.169 x 0.437 What is the concentration of manganese in the original sample?

Final answer should be in ppm

Volume sample, mL Volume 5.0 ppm Mn Volume distilled water, Analytical Signal, mv standard solution, mL mL 000 200 0.031 0.00 1.00 1.00 0.468 0.00 0.75 1.00 0.25 0.574 1.00 0.678 0.50 0.50 1.00 0.75 0.25 0.786 1.00 000 1.00 0.890

Explanation / Answer

Here you have been given the equation which has already been corrected for blank, and is given by:

y = 0.169*x + 0.437 ( I assume that the equation that you intended to write must have been this, because otherwise the equation provided in the text above makes no sense. Even if I assume the equation written alongside, it doesn't account for blank correction because y does not equal 0 when x=0. Nevertheless lets proceed with this assumption, or else provide a corrected equation)

Now, lets assume that the conc. of [Mn] in the sample is 'c'.

Consider the second row of the data provided. Here the volume of sample taken is 1 mL and volume of standard is zero.

Since final volume is 2 mL, this means that sample gets diluted by a factor of 2.

Thus, [Mn] in the mixture due to sample = c/2

Putting this in the equation above gives:

0.468 = 0.169*(c/2) + 0.437

Solving we get:

c = 0.366 ppm

Consider the third row, here volume of sample is 1mL and of standard is 0.25mL

Sample gets diluted 2 times while standard gets diluted 8 times, since final volume is 2 mL.

Thus, equation becomes:

0.574 = 0.169*( c/2 + 5/8 ) + 0.437

Solving we get:

c = 0.371 ppm

In this way calculate 'c' from all rows and get an average value for it.

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.