please & thank you! 9. & 10. & 11. EDTA titration curve: Titrate 50.0 mL of 0.04
ID: 695570 • Letter: P
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please & thank you!
9. & 10. & 11. EDTA titration curve: Titrate 50.0 mL of 0.0400 M Excess EDTA strontium(lI) solution (Sr2) with 0.0800 M EDTA, with the reaction buffered to pH 10.00. The K/ value is 1.6x108 Excess metal 10 Ca2* 1.3 × 1010 a. At 14.0 mL of titrant added, calculate [Sr2-] and pSr2 b. At25.0 mL of ti tran t added, calculate [Sr2+] andps c. At 31.0 mL of titrant added, calculate [Sr2] and pSr2 d. Consult lecture 20 for an example worked out for Ca+ Sr Ca2 equivalence point Kj 1.6 10 sequvalence point The labelled titration curve is for the current strontium problem. 0 5 10 15 20 25 30 35 Volume of EDTA (mL)Explanation / Answer
Calculate the concentration of Sr2+ by adding 14 mL as follows:
Calculate moles of Sr2+ as follows :
Moles of Sr2+= 0.04 M x 50 mL
= 2 mmol
moles of EDTA added = 0.08 M x 14 mL = 1.12 mmol
excess [Sr2+] = 0.88 mmol/64 mL = 0.01375 M
pSr2+ = -log[Sr2+] = 1.86
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2)
Calculate the concentration of SrY2- for the addition of 25 mL EDTA added
moles of Sr2+ = 0.04 M x 50 mL = 2 mmol
moles of EDTA added = 0.08 M x 25 mL = 2 mmol
Equivalence point [SrY2-] formed = 2 mmol/75 mL = 0.0267 M
Let us assume, the change of amount is x and was observed in concentraion of SrY2- at equilibrium
Kf' = [SrY2-]/[Sr2+][EDTA]
1.6 x 10^8 = 0.0267/x^2
By solving x, we get x = 1.3 x 10^-5 M
x = [Sr2+] = 1.3 x 10^-5 M
pSr2+ = 4.90
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3) Calculate the concentration of SrY2- for the addition 31 mL EDTA added as
moles of Sr2+ = 0.04 M x 50 mL = 2 mmol
moles of EDTA added = 0.08 M x 31 mL = 2.48 mmol
[SrY2-] formed = 2 mmol/81 mL = 0.025 M
Calculate concentration of left EDTA as follows:
[EDTA] left = 0.48 mmol/81 mL = 0.006 M
[Sr2+] = 0.025/1.6 x 10^8 x 0.006 = 2.64 x 10^-8 M
pSr2+ = 7.58
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