This set of Analytical Instrumentation Questions and Answers focuses on “Ion Selective Electrodes-Principle and Types”.
1. Which of the following is not the characteristic of ion selective electrodes?
a) It is fragile
b) Easy to use
c) Available in different sizes and shapes
d) It is insensitive to many ions
View Answer
Explanation: Ion selective electrode is rugged in construction. It is highly selective to a particular ion.
2. In glass membrane electrode, the glass containing 11% Na2O, 18% Al2O3, 71% SiO2 is highly sensitive to which of the following ions?
a) Sodium
b) Hydrogen
c) Nitrogen
d) Chlorine
View Answer
Explanation: In glass membrane electrode, the glass containing 11% Na2O, 18% Al2O3, 71% SiO2 is highly sensitive to sodium ions. Glass electrodes can be used to measure various ions by changing the glass membrane composition.
3. In liquid membrane electrode, the liquid ion exchanger is held in a porous disc of _____________
a) Solid material
b) Semi-permeable membrane
c) Hydrophobic material
d) Water absorbing material
View Answer
Explanation: In a liquid membrane electrode, the liquid ion exchanger is held in a porous disc of hydrophobic material. It is water repelling material.
4. In recent liquid membrane electrodes, the porous liquid membrane is replaced with which of the following?
a) Polyvinyl chloride
b) Polyacryl chloride
c) Polyester membrane
d) Polyacryl amide
View Answer
Explanation: In recent liquid membrane electrodes, the porous liquid membrane is replaced with polyvinyl chloride membrane. The measured potential is a direct measure of the concentration of specific ion.
5. Which of the following is used in potassium electrode in liquid membrane electrodes?
a) Ionomycin
b) Valinomycin
c) Nonactin
d) Gramicidin
View Answer
Explanation: Valinomycin is used in potassium electrode in liquid membrane electrodes. It is a doughnut shaped electron rich pocket.
6. In solid state membranes, the body of the electrodes are made of which of the following?
a) Polyvinyl chloride
b) Plastic
c) Polythene
d) Teflon
View Answer
Explanation: In solid state membranes, the body of the electrodes are made of Teflon. The membrane is held in position using epoxy resin.
7. Which of the following is not the characteristic of ion selective electrodes?
a) Simple to use
b) Inexpensive
c) Narrow concentration range
d) Operates in wide range of temperature
View Answer
Explanation: Ion selective electrodes have a wide concentration range. It is highly selective to a particular ion.
8. Ion selective electrode are unaffected by colour or turbidity of the solution.
a) True
b) False
View Answer
Explanation: Ion selective electrode are unaffected by colour or turbidity of the solution. It operates in wide range of temperature.
9. Which of the following is not a problem of ion selective electrodes?
a) Interference with other ions
b) Output is influences by ionic strength
c) Drift in electrode potential during a sequence of measurements
d) Can measure only positive ions
View Answer
Explanation: Ion selective electrodes can measure both positive and negative ions. It is affected by interference from other ions.
10. Which of the following is the effective concentration measured at the electrode head?
a) Selectivity coefficient
b) Ionic strength
c) Activity
d) Activity coefficient
View Answer
Explanation: Activity is the effective concentration measured at the electrode head. Concentration is different from the activity.
11. The value of activity coefficient is always in which of the following ranges?
a) Zero
b) Less than zero
c) Less than 1
d) Greater than 1
View Answer
Explanation: The value of activity coefficient is always less than 1. It is the ratio of activity divided by concentration.
12. Which of the following specifies the relation between ionic strength and activity coefficient?
a) Directly proportional
b) Inversely proportional
c) Equal
d) No particular relation
View Answer
Explanation: Activity co-efficient and ionic strength are inversely proportional to each other. If the ionic strength increases, the value of activity decreases.
13. The difference between measured activity and actual concentration becomes higher at higher concentration. Is this statement true or false?
a) True
b) False
View Answer
Explanation: The difference between measured activity and actual concentration becomes higher at higher concentration. Similarly, it decreases at lower concentrations.
14. Given below is the diagram of liquid membrane electrode. Identify the unmarked component.
a) Solid material
b) Semi-permeable membrane
c) Hydrophobic material
d) Water absorbing material
View Answer
Explanation: The unmarked component is porous hydrophobic material. It holds the liquid ion exchanger.
15. Ion selective electrodes have ________ linear range and _________ detection limit than the pH electrode.
a) Lower, lower
b) Lower, higher
c) Higher, lower
d) Higher, higher
View Answer
Explanation: Ion selective electrodes have a lower linear range and higher detection limit than the pH electrode. It works on effectively narrow pH.
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