How does the Clark polarographic O2 electrode function? a. It ...

[swpotter12]

How does the Clark polarographic O2 electrode function?
 
  a. It measures the magnetic properties of O2 versus N2.
  b. It measures the electrical potential across a Wheatstone bridge.
  c. It uses O2 to produce a reduc-tion-oxidation reaction.
  d. It measures the comparative cooling effect on a heated wire.

Question 2

Under ideal conditions, electrochemical oxygen (O2) analyzers have approximately what degree of accuracy?
 
  a. 1
  b. 2
  c. 3
  d. 4

[joneynes]

Answer to Question 1

ANS: C
This system typically consists of a platinum cathode and a silver-silver chloride anode (Figure 19-1). Oxygen molecules diffuse through the sensor membrane into the electrolyte, where a po-larizing voltage causes electron flow between the anode and cathode. While silver is oxidized at the anode, the flow of electrons reduces oxygen (and water) to hydroxyl ions (OH) at the cath-ode. The more O2 molecules that are reduced, the greater is the electron flow across the poles (current). The resulting change in current is proportional to the PO2, with its value displayed on a galvanometer, calibrated in percent oxygen.

Answer to Question 2

ANS: B
There are two common types of electrochemical oxygen analyzers: (1) the polarographic (Clark) electrode and (2) the galvanic fuel cell. Under ideal conditions of temperature, pressure, and rela-tive humidity, both types are accurate to within 2 of the actual concentration.