Hi Expert! Please answer all the following parts: a) Potassium ion in 250.0 (±0.
ID: 902740 • Letter: H
Question
Hi Expert!
Please answer all the following parts:
a) Potassium ion in 250.0 (±0.1) mL water sample was precipitated with sodium tetraphenylborate.
K+ + (Ph)4B- ==> KB(Ph)4 (s); The precipitate was filtered, washed, dissolved in an organic solvent, and treated with excess Hg(EDTA)2-:
4HgY2- + (Ph)4B- + 4H2O ==> H3BO3 + 4PhHg+ + 4HY3- + OH-
The liberated EDTA was titrated with with 28.73 (±0.03) mL of 0.0437 (±0.0001) M Zn2+. Find [K+] and its absolute uncertainty in the original sample.
B) A 25.00 mL sample containing Fe3+ and Cu2+ required 16.06 mL of 0.05083 M EDTA for complete titration. A 50.00 mL sample of the unknown was treated with NH4F to protect the Fe3+. The Cu2+ was reduced and masked by thiourea. Addition of 25.00 mL of 0.05083 M EDTA liberated Fe3+ from the fluoride complex to for an EDTA complex. The excess EDTA required 19.77 mL of 0.01883 M Pb2+ to reach a zylenol orange end point. Find the [Cu2+] in the original sample?
Thank you in advance!
Explanation / Answer
solution:-
2) the reaction for the lead EDTA complex is
Pb+2 + EDTA-4 -> Pb+2-(EDTA)
25 mL unknown
EDTA to be added =6.06 mL x 0.051 M of EDTA or 0.819 mMoles
50 mL sample requires 0.897 mMoles to react with Fe+3
Half of that is requires = 0.897/2=0.449
=> therefore the remainder is 0.819-0.449 = 0.370 mMoles of Cu^+2
this is 1:1 Cu+2-EDTA complex
therefore the number of mMoles of Cu+2= 0.370mMoles
The Concentration of [Cu^+2] = 0.370mMoles/25 ml =0.0418 M Cu^+2
The answer is [Cu^+2]= 0.0418 M