A researcher is testing the concentration of Lithium in lake water after four ti

ID: 941350 • Letter: A

Question

A researcher is testing the concentration of Lithium in lake water after four times the average signal is 4.463 mV. Determine the concentration of lithium in the water and find the uncertainty of the calculated concentration.

So for the concentration I just graphed it to find the Y=mx+b and plug the signal into the y value to find my concentration is that correct?

I really need help with uncertainty not sure how to go about determing that from the information given

Lithium (ppb) Signal (mV) 0 0 2 0.384 10 0.928 20 1.69 30 2.419 40 7.973 50 4.267 60 5.003 75 6.039 100 7.886 125 8.357 150 8.811

Explanation / Answer

S No

Lithium (ppb)

Signal

(mV)

0.384

0.928

1.69

2.419

3.973

4.267

5.003

6.039

100

7.886

125

8.357

150

8.811

Consider Lithium (ppm) as X axis and signal (mV) as Y axis

Find slope from above table: since X=0, Y=0 shows that this straight line does not have origin with the general formula Y=mX, where m is slope (Y/X)

Average of the slope we will get from the above data is 0.07

(Y3-Y2)/(X3-X2) = (0.928-0.384)/(10-2) = 0.068

(Y4-Y3)/(X4-X3) = (1.69-0.928)/(20-10) = 0.076

Do the same for other data you will get slope average of 0.07 now construct the equation using this slope,

Signal (mV), Y= 0.07*X, lithium(ppb)

Thereore, 4.463 = 0.07*X

So, X = 4.463/0.07 = 63.76 ppb