Determination of Deprotonation Constant of Glycine in 10, 20 and 30% Dioxane in Dioxane-Water System and Related Thermodynamic Quantities at 308.15K by E.M.F. Measurement
DOI:
https://doi.org/10.32628/IJSRSET23103102Keywords:
Deprotonation constant, aquo-organic system, thermodynamic quantities.Abstract
The deprotonation constant (pK1) of glycine in 10, 20 and 30% dioxane in dioxane-water system at 308.15K was determined by potentiometric method using calomel electrode with the help of modified Davies equation, the dissociation of glycine is given as:
ZH+ Z± + H+
m2(1-?) m2? m2?
where ZH+ = NH3+-CH2-COOH
Z± = NH3+-CH2-COO- (Zwitter ion)
and Z = NH2-CH2-COOH = glycine
k1 = acidic dissociation constant
k1 is given by:
log k1 = log k1(A) - (2A¢√μ/(1+ √μ)) + ?1μ
where k1 real dissociation constant
k1(A) = Apparent Dissociation Constant
Rearrangingthe above equationwe have:
log K1 - ?1μ = logK1(A) - (2A1√μ) / (1 + √μ)
= q where q = log K1(A) - (2A1√μ) / (1 + √μ)
or q = log K1- ?1μ
-q = pK1 + ?1μ
The constant value of mH+ was calculated by:
log mH+ = (E0 - E)/K - log mCl_ + (2A¢√μ/(1+ √μ)) - ?1μ
The value of deprotonation constant was calculated by extrapolating graph at μ = 0 where is μ is ionic strength.The related thermodynamic quantities ΔG0, ΔH0 and ΔS0 and free energy transfer ΔGt were calculated by the following least square method.The deprotonation constant was calculated by least square method:
log K1 = -A*/ T + D*-C*T
The related thermodynamic quantities ΔG0, ΔH0 and ΔS0 and free energy transfer ΔGt was calculated by the following least square method:
ΔG0 = -19.1438(-A* + D*T - C*T2)
ΔH0 = -19.1438(-A*- C*T2)
ΔS0 = -19.1438(D* - 2C*T)
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