7-15. A cyanide solution with a volume of 12.73 mL was treated with 25.00 mL of Ni²+ solution (containing excess Ni?+) to convert the cyanide into tetracyanonickelate(II): 4CN + Ni²+ → Ni(CN); The excess Ni²+ was then titrated with 10.15 mL of 0.013 07 M ethylenediaminetetraacetic acid (EDTA): Ni?+ + EDTA'- → Ni(EDTA)² Ni(CN); does not react with EDTA. If 39.35 mL of EDTA were required to react with 30.10mL of the original Ni²+ solution, calculate the molarity of CN in the 12.73-mL cyanide sample.

Hh.88.

7.00 mL of 6.00 x 103 M Fe(NO3)3 (6.00 times 10 to the minus 3rd power MFe (NO3)3) is added to 4.00 mL of 8.00 x 103 M KSCN (8.00 times 10 to the minus 3rd power M KSCN) along with 7.00 mL of water. The concentration of [F e(SCN)2+] was found to be 1.00 x 103 M (1.00 times 10 to the minus 3rd power M) at equilibrium. How many initial moles of SCN (SCN minus) are present in the solution? Express your answer as a decimal number (no exponents). Your Answer: Answer units

9.00 mL of 6.00 x 103 M Fe(NO3)3 (6.00 times 10 to the minus 3rd power M Fe (NO3)3) is added to 5.00 mL of 6.00 x 10-3 M KSCN (6.00 times 10 to the minus 3rd power M KSCN) along with 4.00 mL of water. The concentration of [F e(SCN)2*] was found to be 1.00 x 10-4 M (1.00 times 10 to the minus 4th power M) at equilibrium. How many moles of SCN" (SCN minus) are present in the solution at equilibrium? Express your answer as a decimal number (no exponents). Your Answer: Answer units

What is the concentration of S2- in equilibrium with MnS(s) (Ksp [S²] = M = 4.6 x 10-¹4) and 0.098 M Mn²+?

25.00 mL 0.01000 M Ni2+ is titrated with 0.01000 M EDTA in a solution buffered to pH 5.0. Given that the formation constant for the Ni-EDTA (NiY2–) chelate is 4.2 x 1018 and the 4 value at pH 5.0 is 3.54 x 10–7 An indicator (Ind) forms a metal-indicator complex with Ni2+ (NiInd), giving aconditional formation constant of 1.00 x 108 at pH 5.0. It is generally assumedthat human eyes can detect about 1 part of one color in 10 parts of another;therefore, the first discernible color change will occur when the [NiInd]:[Ind]ratio changes from 10 to about 0.1.

25.00 mL 0.01000 M Ni2+ is titrated with 0.01000 M EDTA in a solution buffered topH 5.0. Given that the formation constant for the Ni-EDTA (NiY2–) chelate is4.2 x 1018 and the 4 value at pH 5.0 is 3.54 x 10–7. Explain briefly why EDTA is an important reagent used in complexometrictitrations.