Calibration data for a bromide ion‑selective electrode (ISE) was collected and recorded in the table. The potential of the ISE was measured against a saturated calomel electrode (SCE). All solutions were buffered at a pH of 7.56. A linear calibration curve can be constructed from this data as a plot of potential (in mV) vs. pBr. Determine the slope and y‑intercept of such a plot of the calibration data given.
Br-M | Potential (mV |
0.300 | -21.6 |
0.0300 |
36.7 |
0.00300 | 96.5 |
0.000300 | 154.8 |
0.0000300 | 224.4 |
slope=
mV
y‑intercept=
mV
Two unknown solutions were tested for [Br−] using the same bromide ISE. The potential reading for unknown 1 was −6.3 mV, and the potential reading for unknown 2 was 198.2 mV. Using the calibration curve you constructed, determine the concentration of Br− in each unknown solution.
unknown 1 [Br−]=
unknown 2 [Br−]=
slope = 61.01 mV
y-intercept = -55.761 mV
unknown 1 [Br-] = 0.155 M
unknown 2 [Br-] = 6.88 x 10-5M
Explanation
The equation of best fit line is : y = 61.01x - 55.761
slope = 61.01 mV
intercept = -55.761 mV
For unknown 1, potential = -6.3 mV = y
From the equation o best fit line,
x = (y + 55.761) / 61.01
x = (-6.3 + 55.761) / 61.01
x = 0.8107
pBr = 0.8107
-log[Br-] = 0.8107
[Br-] = 10-0.8107
[Br-] = 0.155 M
Calibration data for a bromide ion‑selective electrode (ISE) was collected and recorded in the table. The...
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Calibration data for a bromide ion-selective electrode (ISE) was collected and recorded below. The potential of the ISE was measured against a saturated calomel electrode (SCE). All solutions were buffered at a pH of 7.56. A linear calibration curve can be constructed from this data as a plot of potential (in mV) vs. pBr. Determine the slope and y-intercept of such a plot of the calibration data given [Br] (M) Potential (mV) 0.300 0.0300 0.00300 96.4 0.000300 155.1 0.0000300 224.8...
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