(a)
Interpretation:
The calibration of calcium ion selective electrode is used for the determination of pCa and the table for this data is shown below-
5.00 | -53.8 |
4.00 | -27.7 |
3.00 | +2.7 |
2.00 | +31.9 |
1.00 | +65.1 |
The relation between potential and the and the pCa is linear. Using the data, a least square straight line is to be plotted using the spreadsheet.
Concept introduction:
The least square method is a method in which the best result is obtained for the set data point by minimizing the sum of offset or residuals from the plot of curve statistically.
(b)
Interpretation:
The least square expression is to be determined for the best straight line through the point.
Concept introduction:
The least square method is a method in which the best result is obtained for the set data point by minimizing the sum of offset or residuals from the plot of curve statistically.
(c)
Interpretation:
The standard deviation is to be determined for the slope and the intercept of the least-square line.
Concept introduction:
The slope of line is also called as gradient of line which is used to define the direction and steepness of the line.
The intercept line is the y −axis of line at which point it crosses X −axis.
(d)
Interpretation:
The value pCa of serum solution is to be determined in which the electrode potential value is 10.7mV. The absolute and relative standard deviation for pCa is to be determined when obtained result is from the single voltage measurement.
Concept introduction:
The standard deviation method is used for the quantification of the amount of variation or for the dispersion for the set of the data values.
(e)
Interpretation:
The absolute and relative standard deviation for pCa is to be determined when the result obtained from the part (d) in millimeters is the mean value of two replicate measurements and this calculation is to be repeated for the eight measurements.
Concept introduction:
The standard deviation method is used for the quantification of the amount of variation or for the dispersion for the set of the data values.
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Chapter A1 Solutions
Principles of Instrumental Analysis
- An ion-selective electrode (ISE) produces voltage output (mV) proportional to solution pH. You have three standard pH solutions (4, 7, and 10). Assuming that pH 7 buffer solution is used together with pH 4 for calibration prior to measuring acidic solutions and together with pH 10 before measuring alkaline solutions, produce a flowchart of the calibration routine for a single pH ISE.arrow_forwardThe table below describes a procedure in preparing standard solutions of a protein sample with different concentrations. (A) Determine the concentrations of each tube if the starting concentration of the protein is 500 mg mL (B) Determine the equation of the line if the concentration (x-axis) was plotted vs the absorbance (y-axis). (C) What is the concentration, in mg mL, of the diluted unknown protein sample if the absorbance at 595 nm is 0.333? L-1. Tube Volume of protein, Volume of water, Final concentration, Absorbance #3 mL mL (at 595 nm) mg mL-1 0.00 5.00 0.113 12 0.70 4.30 0.184 3 1.40 3.60 0.251 14 2.10 2.90 0.329 15 2.80 2.20 0.385 3.50 1.50 0.454 17 4.20 0.80 0.503 8 5.00 0.00 0.577 Suppose that the unknown protein (diluted) sample in 4.C was diluted from a protein stock solution. Determine the concentration of the original unknown protein stock solution if 2.00 mL of the protein solution was mixed with 8.00 mL of water to create the unknown protein (diluted) sample in 4.C.arrow_forwardA chemist obtained the following data for percent lindane in the triplicate analysis of an insecticide preparation: 7.23, 6.95, and 7.53%. Calculate the 90% confidence interval for the mean of the the three data, assuming that (a) the only information about the precision of the method is the precision for the three data. (b) on the basis of long experience with the method, it is believed that s---->σ lindane. (c) If s=0.28 is good estimate of σ, how many replicate measurement should be made in order for the mean for the analysis of sample to be within 0.2% of the true mean 90% of the time.arrow_forward
- A water sample was analyzed for Fe content using the iron-phenanthroline method. The following data were obtained from the analysis: Determine the value of the slope (m), y-intercept (b), and the coefficient of determination (r2)arrow_forwardAn analyst wants to find out the active surface of his electrode before conducting his analyzes. To do this, he carried out a series of measurements by cyclic voltammetry (CV) using a 1 mM solution of K4Fe(CN)6 dissolved in 0.1M NaCl. He recorded the anodic peak intensity (ip) corresponding to the oxidation of Fe(II) to Fe(III) as a function of the scanning speed (v) of the CV (see table). What is the active surface of the electrode? Data: Fe diffusion coefficient (CN)64-, D = 6.67x10-6 cm2/s Randles-Sevcik equation ip = (2,69x105)n3/2ACD1/2v1/2 rate (v/s) ip (A) 5,00E-02 5,75E-05 1,00E-01 7,68E-05 2,00E-01 9,94E-05 5,00E-01 1,42E-04 1,00E+00 2,07E-04arrow_forwardCalibration of a glass electrode gave a reading of 126.5 mV with a 0.05 m potassium hydrogen phthalate buffer standard ( pH = 4.015), and a reading of -73.7 mV with a 0.008695 m potassium dihydrogen phosphate, 0.0343 m disodium hydrogen phosphate buffer standard (pH = 7400), both measured at 30 C. What is the observed slope (mV/pH unit) of the calibration curve? slopeurd= -59.17 mV/pH What is the theoretical slope at 30 C? 0.984 mV/pH slopeeical= What is 8. the electromotive efficiency, to three significant figures?arrow_forward
- Calibration of a glass electrode gave a reading of 134.9 mV with a 0.05 m potassium hydrogen phthalate buffer standard ( pH = 4.015), and a reading of -69.1 mV with a 0.08 m HEPES, 0.08 m NaHEPES, 0.08 m NaCl buffer standard (pH = 7.454), both measured at 30 °C. What is the observed slope (mV/pH unit) of the calibration curve? slope observed slope theoretical What is the theoretical slope at 30 °C? pH -58.1 5.29 Incorrect What is the pH of an unknown that gives a reading of 41.4 mV with this electrode at 30 °C? Incorrect Incorrect mV/pH mV/pHarrow_forwardQ4 (a) Analyze the importance of dropping mercury electrode on polarography. (b) (i) Calculate the molarity of MgSO4 in a solution containing 1.5 g ofMgSO4 in a volume of 250 mL?(ii) Calculate the weight of MgSO4 in grams which is present in 100mL of 0.076 M MgSO4?(c) Evaluate the key differences between paper chromatography and gaschromatographyarrow_forward(3) A nitrate -selective electrode and a reference electrode were dipped into a solution of nitrate with an activity of 1.00 x10 ³M, and the potential of the nitrate selective electrode was found to be -22.4 mV. The same electrode couple was then dipped into a solution containing nitrate and chloride each of which had an activity of 1.00 x 10³M. The potential of the nitrate- selective electrode in this solution was -124.8 mV. Th temperatures of both solutions were 25°C. Calculate the selectivity coefficient of the nitrate -selective electrode for chloride.arrow_forward
- Calibration of a glass electrode gave a reading of 139.3 mV with a 0.05 m potassium hydrogen phthalate buffer standard ( pH = 4.015), and a reading of -160.7 mV with a 0.01 m borax buffer standard (pH = 9.139), both measured at 30 °C. What is the observed slope (mV/pH unit) of the calibration curve? slope observed What is the theoretical slope at 30 °C? = slope theoretical pH : What is the pH of an unknown that gives a reading of 42.5 mV with this electrode at 30 °C? = = mV/pH mV/pHarrow_forwardProvide as many error sources in your calibration of the ion-selective electrode (ISE) as you can.arrow_forwardThe sensitivity of a coulometer is governed by the delivery of its minimum current for its minimum time. Suppose that 5 mA can be delivered for 0.1 s.(a) How many moles of electrons are delivered at 5 mA for 0.1 s? (b) How many milliliters of a 0.01 M solution of a two-electron reducing agent are required to deliver the same number of electrons?arrow_forward
- Principles of Instrumental AnalysisChemistryISBN:9781305577213Author:Douglas A. Skoog, F. James Holler, Stanley R. CrouchPublisher:Cengage Learning