Question

A solution containing 30.00 ml of 0.0500 M metal ion buffered to pH = 10.00 was titrated with 0.0400 M EDTA. Answer the following questions and enter your results with numerical value only. Calculate the equivalence volume, Ve, in milliliters.

Calculate the concentration (M) of free metal ion at V = 1/2 V_e.

Calculate the fraction (α_Y^4-) of free EDTA in the form Y^4-. Keep 2 significant figures.

If the formation constant (K_f) is 10^12.00. Calculate the value of the conditional formation constant K_f’ (=α_Y^4- * K_f) and enter your result as scientific notation form.

Calculate the concentration (M) of free metal ion M⁺ at V = V_e. (Use the K_f' calculated above)

I'm stuck because theres no other information is provided nor given.

Answer 1

Equivalence Volume = (Concentration of metal ion x Volume of metal ion)/concentration of EDTA

= (0.05 x 30)/0.04

= 37.5 ml

Volume of free metal ion at {V = 1/2 Ve = 18.75 ml} = 15 ml

Volume of total solution at {V = 1/2 Ve = 18.75 ml} = 30+18.75 = 48.75 ml

concentration (M) of free metal ion at {V = 1/2 Ve = 18.75 ml} = (0.05 x 15)/48.75

= 0.01538 M

fraction (αY4-) of free EDTA in the form Y4- = α_Y4- x concentration of EDTA

= 0.36(taken from literatute for pH = 10)x 0.04

= 0.0144 M

conditional formation constant Kf’ = 0.36 x 1012

= 364.32