1.12: Electrochemical Measurements
- Page ID
- 125322
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- The antibiotic Valinomycin has a high affinity for:
- sodium
- lithium
- potassium
- calcium
- magnesium
- In the Nernst equation, E0 represents:
- measured volume
- gas constant
- electrons transferred
- Faraday constant
- standard half cell potential
Match the items in Column B with the definitions in Column A for questions 3-7:
B
|
A
|
- The K ion electrode has an absolute specificity for K and therefore has interferences from no other cations.
- true
- false
- The PCO2 electrode reduces O2 to H2O and measures the resulting decrease in current
- true
- false
- The statement which most correctly describes the measurement of pH with a glass electrode is:
- hydrogen ions pass through a special kind of permeable glass
- the internal and external half-cells have the same potential
- a special kind of glass sensitive to hydrogen ions is used
- the temperature knob on the pH meter compensates for the influence of temperature
- temperature is not involved with pH measurements
- In potentiometric measurements, the voltage difference between the indicator and reference electrodes is proportional to:
- ion concentration (mmol/L)
- ion activity
- log of ion concentratioin (mmol/L)
- log of ion activity
- ion concentration (mg/L)
- In the PCO2 electrode, all of the following are true except:
- carbon dioxide from the sample chamber diffuses through a membrane and dissolves in electrolyte solution
- the PCO2 electrode measures pH change caused by the production of carbonic acid
- the measuring electrode is a CO2 specific electrode
- the measuring and reference electrodes are combined into one unit
- the CO2 measurement can be related to total CO2
Use the following Key to answer Questions 13 - 19:
- 1, 2, and 3 are correct
- 1 and 3 are correct
- 2 and 4 are correct
- only 4 is correct
- all are correct
- The CO2 electrode works by:
- measuring a potentiometric change
- measuring a change in current
- measuring a change in pH
- using an enzymatic reaction with CO2
- Ion selective electrodes:
- allow ion exchange on surface resulting in a change of potential
- are pH dependent
- are temperature dependent
- do not require a reference electrode
- Potentiometry:
- is the measurement of the electrical potential difference between two electrodes in an electrochemical cell
- measures voltage
- applications include pH and PCO2 measurements
- principles are used for measuring potassium using valinomycin membrane
- Which of the following devices are considered to be of the amperometric—coulometric type?
- PO2 electrode
- pH electrode
- Chloridometer (Cotlove)
- PCO2 electrode
- A KCl salt bridge, widely utilized in electrochemical cells, has all of the following functions except:
- lowers liquid—junction potentials
- conducts electricity
- allows ions to migrate
- measures the potential between two solutions
- The PCO2 electrode of a blood gas instrument measures:
- reduction of CO2 at the cathode
- change in pH of the electrode solution
- the time required for CO2 to pass through a special membrane
- partial pressure of CO2
- Which statement(s) is/are false concerning the chloridometer?
- generating anode generates silver ions
- electrons from the generating electrodes combine with hydrogen ions to form hydrogen gas
- automatic timer is initiated at the start of the silver ion generation
- AgCl is sensed by the detector electrode
- Answer
-
- c (p. 277)
- e (p. 274)
- d (p. 282)
- c (p. 285)
- b (p. 283)
- a (p. 282)
- a (p. 282)
- b (p. 277,280)
- b (p. 279-282)
- c (p. 278-279)
- d (p. 274,276)
- c (p. 279)
- b (p. 279)
- a (p. 276-277)
- e (p. 273-274)
- b (p. 282-285)
- d (p. 273)
- c(p. 279)
- c (p. 285)