Final answer:
Potassium oxalate acts as an anticoagulant by removing calcium ions from blood serum, which is essential for preventing coagulation. The necessary amount is calculated based on the initial concentration of calcium ions and the volume of serum in the blood sample.Answer is OPTION A.
Step-by-step explanation:
The mode of action of potassium oxalate, K2C2O4, is as an anticoagulant in blood collection. It works by chelating calcium ions (Ca2+) in the blood serum, forming an insoluble salt, calcium oxalate monohydrate (CaC2O4 H2O), which removes the calcium ions that are necessary for the coagulation process. To calculate the mass of potassium oxalate needed to prevent coagulation, we consider the concentration of calcium ions in normal serum and the proportion we must leave unprecipitated to keep the blood from clotting.
Given that the blood serum contains 9.5 mg of Ca2+ per 100 mL, we can find out how much calcium is in a 5.5 mL serum of a 10 mL blood sample (which is 55% serum by volume). Then we'll determine the amount of calcium that must be left (1.0%) to maintain its anticoagulant function. Finally, we'll use the stoichiometry of the reaction between calcium ions and potassium oxalate to find out the required mass of K2C2O4.