Which chemical reaction occurs within the Stow-Severinghaus ...

[geodog55]

Which chemical reaction occurs within the Stow-Severinghaus electrode?
 
  a. CO2 + H2O  H2CO3  H+ + HCO3
  b. O2 + 2H2O + 4e  4OH
  c. 4Ag  4Ag+ + 4e
  d. EH+ = 0.0615  pH

Question 2

In a partial pressure of oxygen (PCO2) electrode, carbon dioxide does which of the following?
 
  1. It reacts with potassium chloride.
  2. It reacts with water to form carbonic acid.
  3. It diffuses through a polyethylene membrane.
  4. It diffuses through a semipermeable Teflon membrane.
  a. 2 and 3 c. 1 and 4
  b. 1 and 3 d. 2 and 4

[tjayeee]

Answer to Question 1

ANS: A
The Stow-Severinghaus electrode is the standard PCO2 electrode. Within the electrode, CO2 from the blood diffuses across the Teflon membrane and reacts with water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate. The reaction can be written as CO2 + H2O  H2CO3  H+ + HCO3. The hydrogen ions from the bicarbonate-buffered solution then diffuse across the glass electrode, and the pH of the solution is measured as it is in the pH electrode.

Answer to Question 2

ANS: D
A PCO2 electrode is basically a pH electrode covered with a carbon dioxidepermeable Teflon or silicone (Silastic) membrane. A bicarbonate-buffered solution is held between the Teflon mem-brane and the pH glass electrode by a nylon spacer. CO2 from the blood diffuses across the sem-ipermeable Teflon membrane and reacts with the water to form carbonic acid, which dissociates into hydrogen ions and bicarbonate.

[geodog55]

Thank you

[tjayeee]

No problemo