You are measuring Ca2+ in drinking water using an ISE. You diluted 1 mL of the d
ID: 936782 • Letter: Y
Question
You are measuring Ca2+ in drinking water using an ISE. You diluted 1 mL of the drinking water with 19 mL ddH2O. You have standards of Ca2+ in ddH2O. You add 1 mL of a commercial ISA reagent to 20 mL of each standard or the diluted sample. You then measure the ISE response of each sample using the voltmeter. The following data are obtained:
ID
mV
Ca2+ (?g/L)
Standard
22.07
0.12
Standard
45.11
1.08
Standard
75.92
11.5
Standard
100.34
178
Standard
116.97
1,206
Standard
161.55
20,045
Sample
67.83
?
What is the concentration of Ca2+ in the diluted drinking water (?g/L)?
ID
mV
Ca2+ (?g/L)
Standard
22.07
0.12
Standard
45.11
1.08
Standard
75.92
11.5
Standard
100.34
178
Standard
116.97
1,206
Standard
161.55
20,045
Sample
67.83
?
Explanation / Answer
use the values to prepare a line and you can calculate the concentration trough the linear equation
(are you sure about the values? I didn`t use the value at 116. its to far away and at 100 i used 17,8 otherwise it will not fit
y = 0.1597*67.83 -2,8458 = 7.99 = conc of Ca+ in sample
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