(a) Why the chloride concentration of RBC in venous blood is more than that of RBC in arterial blood ?

Explanation

(a) During `CO_(2)` transport by venous blood `KHCO_(3)` formed in RBC dissociates into `K^(+) and HCO_(3)^(-)` ions. At the same time NaCl in plasma dissociates into `Na^(+) and Cl^(-)` ions.
To maintain acid-base and ionic balance, ` HCO_(3)^(-)` ions move from RBC to plasma and `Cl^(-)` ions move from plasma to RBC in exchange to that. (RBC membrane is impermeable to `Na^(+) and K^(+)` ions). That is why RBC in venous blood contains more chloride than RBC of arterial blood.
(b) During `CO_(2)` transport by venous blood, `CI^(-)` ions move with `H_(2)O` (chloride and water shift) from plasma to RBC. That is why the volume of RBC in venous blood is more than RBC in arterial blood.