Calcium levels in blood can be determined by adding oxalate ion to precipitate c
ID: 528554 • Letter: C
Question
Calcium levels in blood can be determined by adding oxalate ion to precipitate calcium oxalate, CaC2O4, followed by dissolving the precipitate in aqueous acid and titrating the resulting oxalic acid (H2C2O4) with KMnO4:5H2C2O4(aq)+2MnO4(aq)+6H+(aq)10CO2(g)+2Mn2+(aq)+8H2O(l)
Part A
How many milligrams of Ca2+ are present in 10.5 mL of blood if 21.42 mL of 9.90×104 M KMnO4 solution is needed for the titration?
Calcium levels in blood can be determined by adding oxalate ion to precipitate calcium oxalate, CaC2O4, followed by dissolving the precipitate in aqueous acid and titrating the resulting oxalic acid (H2C2O4) with KMnO4:5H2C2O4(aq)+2MnO4(aq)+6H+(aq)10CO2(g)+2Mn2+(aq)+8H2O(l)
Part A
How many milligrams of Ca2+ are present in 10.5 mL of blood if 21.42 mL of 9.90×104 M KMnO4 solution is needed for the titration?
mCa2+ = mgExplanation / Answer
from the balanced equation,
moles of H2C2O4, n1 = 5 mol and moles of MnO4-, n2 = 5 mol
Formula,
M1 V1 / n1 = M2 V2 / n2
M1 * 10.5 / 5 = 9.90 * 10-4 * 21.42 / 2
M1 = molarity of oxalic acid = 5.05 * 10-3 M
Moles of Ca2+ = 5.05 * 10-3 * 10.5 / 1000 = 5.30 * 10-5 mol
Now, mass of Ca2+ = 5.30 * 10-5 * 20 = 1.06 * 10-3 g. = 1.06 mg.