[Einadin]

how do i solve this? i read arond 7 books.. these problems are the ones i cant solve... please i need to learn how to do the methods in solving them.. cause i have to self study due to the fact that i wasnt offered the laboratory course of analytical chemistry...

Calculate the volume of 0.050 M EDTA needed to titrate
a. Ca in 0.1973g of CaCO3
b. The Ca in 0.5140g mineral specimen that is 81.4% brushite CaHP04*2H20(172.09g/mol)
c. Ca and MG in a 0.1414g sample that is 92.5% dolamite CaCO3*MgCO3(184.44g/mol)

2. sulfide ion was determined by indirect titration with EDTA to a solution containing 25ml of 0.04332M Cu(ClO4)2 plus 15ml of 1M acetate buffer (PH. 4.5) were added to 25ml of unknown sulfied solution with vigorous stirring. the CuS precipitate was filtered and washed with hot Water. then ammonia was added to the filtrate which contained the excess Cu2+ until the blue color of Cu(NH3)4^2+ was observed titration with 0.03927M EDTA required 12.11ml to reach the murexide end point Calculate the concentration of sulfide in the unknown

[Einadin]

need your help guys that badly.. i came on this forum desperate for answers i need to grad this year baaad

[AWK]

1,2. Hint
EDTA reacts with Cu²⁺, Ca²⁺ and Mg²⁺ in 1 mole to 1 mole ratio.
2. Hint
Moles of Cu²⁺ in perchlorate = moles of Cu₂S + moles of Cu₂₊ titrated by EDTA

[Einadin]

ok with question one.. so Ca in CaCO3 do i do this...
0.01973/MM which is 100.09 = moles of CaC03

then

Moles of CaCO3 x 40.08 (mass of Ca)

then divide by 0.050 Mole of EDTA?

is that it?

[Einadin]

also i stated earlier that this subject was ON the analytical chem laboratory class.. and since i wasnt able to enroll in it due to conflict in my schedule i had to self study so i dont get some of the hints sorry 

[Einadin]

can anybody guide m?

[DrCMS]

As AWK told you already

1,2. Hint
EDTA reacts with Cu²⁺, Ca²⁺ and Mg²⁺ in 1 mole to 1 mole ratio.
2. Hint
Moles of Cu²⁺ in perchlorate = moles of Cu₂S + moles of Cu₂₊ titrated by EDTA

For Q1
How many moles of Ca are in 1 mole of CaCO₃?
How many moles is 0.1973g of CaCO₃?
How many moles of EDTA react with that much Ca?
How many mls of 0.05M EDTA contain that many moles?

[Einadin]

so its

40.08/100.09 (grams of Ca/Molecularmass of CaC03) = moles of Ca

then

(moles of CA X 0.1973ml (convert grams to ml))/0.050

i got 1.580 ml

correct?