When blood is donated, the receiving bag contains sodium oxalate (Na2C2O4) solution which precipitates the Ca2+ions as CaC2O4 to prevent clotting. If normal blood has 11.5 mg Ca2+/100 mL and a receiving bag collects 500 mL of blood, what is the minimum concentration of sodium oxalate needed to precipitate all the Ca2+? Assume that 10.0 mL of sodium oxalate solution are added to the bag and that all the calcium precipitates.

Question

When  blood  is  donated,  the  receiving  bag  contains  sodium  oxalate  (Na2C2O4)  solution  which precipitates the Ca2+ions as CaC2O4  to prevent clotting. If normal blood has 11.5 mg Ca2+/100 mL and a receiving bag collects 500 mL of blood, what is the minimum concentration of sodium oxalate needed to precipitate all the Ca2+? Assume that 10.0 mL of sodium oxalate solution are added to the bag and that all the calcium precipitates.

aaronq · Answer

do you have an idea of how to approach the question?

anonymous · Answer

nope but i know i must use the 57,5 mg of ca2+ but i got stuck and things fell apart
pls help

anonymous · Answer

i used the number of moles of ca2+ which is 1.43 moles and shares a 1:1 ratio with Na2C2O4 if this fact is true i managed to get an answer of 143,46M...is this correct?

anonymous · Answer

help?

aaronq · Answer

how did you get 1.43 moles? you only had 57.5 mg (or 0.0575 g)

aaronq · Answer

your train of thought is correct. 

after you found the moles of Ca2+, you used:

M1V1=M2V2, right?

anonymous · Answer

yep sorry i didnt notice it mg i thought it was just grams.tnx

aaronq · Answer

watch your units, dude !

anonymous · Answer

tnx man they love to penalize us on that!!!!