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Citra Angraini
Indri Savitri
Yuliana
Group 13
Multiplication Equations (2:56) with z+ produces 2 = - v z - z + and multiplication Equation (2:56) with z – generating v-z -
2 = -v+ z+ z -.
Summing both produce:
)()(v 22 vvzzvvzzzvz (2.57)
By using the value - the value of SI for = 78.38, kg / m3 for water at 25 ° C and 1 atm into equation (2:58) then:
A = 1.1744 (kg / mol) 1/2,
B = 3.285 x 109 (kg / mol) 1 / 2m-1.
Because negative. Debye-Huckel equation substitution (2.50) into equation (2:54) followed by the use of equation (2:57) yields:
2/1
2/1
1ln
m
m
BaI
AIzz
(2.58)
With mensubsitusikan value - the value of A and B into Equation (2:58) and dividing A by 2.3026 to convert it into a log shape, we obtain:
2/1
2/1
)/)(/(328,01510,0log
om
o
om
mIAa
mI
zz
(2.59)
For very dilute solutions, very small and the second term in the denominator of equation (2:59) is negligible compared to 1. Therefore, for very dilute solutions:
2/1log mAIzz (2.60)
and for very dilute solutions with solvent water at 25 ° C:
2/1)/(510,0log om mIzz
Equation (2.60) is called the Debye-Huckel law limited (Debye-Huckel Limiting Law, DHLL), because it applies only to the limit of infinite dilution.
Application of Equilibrium Constants Determination DHLL on Ion
Equilibrium constants Weak Acid
Determination of the equilibrium constant can help calculation of activity coefficients and vice versa. The procedure can be illustrated with reference to the dissociation of acetic acid, CH3COOH CH3COOH(aq) H
+(aq) + CH3COO-
(aq)
Equilibrium constants is given by:
uCOOHCH
COOCHHa
COOHCH
HCOOCHa
K
a
aaK
3
3
3
3
(2.61)
With mengganti by and by taking the logarithm Equation (2.61) becomes:
log2loglog
3
3 oKCOOHCH
COOCHH
which we can then write:
log2log
1log
2oK
c (2.62)
If the only solution containing acetic acid, ionic strength, given by:
cccI 22 )1(12
1
Further usual plot left side of equation (2.62) for = 0 gives the price Ko, as shown in Figure 2.14.
The results of solubility constant time
Now we will look at an example, in this case the solubility product of silver chloride, that disclosure would be more accurate to liveliness.AgCl(s) ↔ Ag+
(aq) + Cl-(aq)
101010
2
log2loglog ClAgK
ClAg
ClAgaaK
sp
ClAgsp
for a solution that does not have a namesake ions, solubility is:
101010
10102
10
loglog2
1log
log2loglog
sp
sp
Ks
Ks
ClAgs
Extrapolation to zero ionic strength, giving the log price = 0, and provide price ½ log Ksp obtained as a cut point.