Quantitative Analysis Chemistry

Question

Calculate [HY3−] in a solution prepared by mixing 10.00 mL of 0.0335 M VOSO4, 9.90 mL of 0.0335 M EDTA, and 10.00 mL of buffer with a pH of 4.00. At ph 4 Values of α_Y⁴_- for EDTA at 25°C and μ = 0.10 M is 3.0x10^-9.

Answer 1

The Total Volume = 10.00mL+9.90mL+10.00mL=29.90mL=0.0299L

The moles of EDTA in the solution are:

Moles of EDTA=Molarity×Volume (L) =0.0335 M× (9.90/1000) =3.3165×10⁻⁴ mol

The concentration of EDTA in the final solution is:

Concentration of EDTA= Moles of EDTA / Total Volume ​=3.3165×10^−4​/0.0299 = 0.0111M

At pH 4, most EDTA exists as HY³, with α_Y^4-−=3.0×10⁻⁹

The fraction of HY³⁻ is approximately 1−α_Y⁴, so the concentration is:

[HY³⁻]=0.0111 M × (1−3.0×10⁻⁹)≈0.0111 M