# EDTA titration lab help

by higherme
Tags: edta, titration
 P: 129 My question is: Using the average [EDTA], find the weight% of Ca2+ in the unknown My attempt: so, the[EDTA] i found from standardizing was 0.005 M; I used 29.85mL to of EDTA to titrate my 25.00mL unknown and the weight of my unknown used was 0.2505 g this is what i did: [EDTA] = 0.005M * 0.02985L = 1.489E-4 mol EDTA = mol Ca2+ so that is the moles of Ca2+ , my question is do I have to convert this moles to moles in 250mL, because the unknown was prepared in a 250mL volumetric flask, and only 25.00mL was taken out from that flask for titration. Does that mean 1.489E-4 moles (calculated above) is only the amount of moles in 25.00mL??????? any help appreciated :P
HW Helper
PF Gold
P: 3,724
 Quote by higherme My question is: Using the average [EDTA], find the weight% of Ca2+ in the unknown My attempt: so, the[EDTA] i found from standardizing was 0.005 M; I used 29.85mL to of EDTA to titrate my 25.00mL unknown and the weight of my unknown used was 0.2505 g this is what i did: [EDTA] = 0.005M * 0.02985L = 1.489E-4 mol EDTA = mol Ca2+ so that is the moles of Ca2+ , my question is do I have to convert this moles to moles in 250mL, because the unknown was prepared in a 250mL volumetric flask, and only 25.00mL was taken out from that flask for titration. Does that mean 1.489E-4 moles (calculated above) is only the amount of moles in 25.00mL??????? any help appreciated :P
Of course!
 P: 129 so do i have to use m1v1=m2v2 to find the moles that is in 250mL can i just use the number in moles for m1.... or do i have to change it to concentration first (1.489E-4 mol)(25.00mL) = m2 (250mL) m2 = 1.489 E-5 moles in 250mL ??? this is the moles of Ca2+ in the unknown... i divide by the total weight of the unknown to find the % Ca2+
 Sci Advisor HW Helper PF Gold P: 3,724 EDTA titration lab help You are given the weight of the unknown as 0.2505. You dissolved this into 250 mL and analyzed a 25 mL aliquot of this unknown using 29.85 mL of 0.005 M EDTA. You used 25 mL out of a solution of 250 mL. What fraction of 250 mL is 25 mL? That math is pretty simple.
 P: 129 so in 250mL i have 1.48E-4 mol 25 ml /250 ml = 0.1 0.1*1.48E-4 mol = 1.48E-5 mol.... which will be the same as what i got using mv=mv