Question

when u 7-6.Calculate the activity coefficient of Zn2 when p using (a) Equation 7-6; (b) linear interpolation in Table 7-1 0.083 M by 0.083 M by .3+..ban

Answer 1

a)

We have Debye Huckel equation : log = ( - 0.51 z ²) / ( 1 + ( / 305)

Where is activity coefficient, z is charge on ion, is ion size and is ionic strength.

For Zn ²⁺, z = +2 , = 600 pm and _$\mu$ = 0.083 M

log = ( - 0.51 (+2) ²0.083 ) / ( 1 + (600 0.083 / 305 )

log = ( - 0.5877 ) / ( 1 + 0.567)

log =   ( - 0.5877 ) / 1.567 = - 0.3750

= 10 ^{- 0.3750} = 0.4216 = 0.422

ANSWER : Zn ²⁺ = 0.422

b)

$\mu$	Zn 2+
0.1 M	0.405
0.05 M	0.485

When $\Delta$$\mu$ = ( 0.10 M - 0.05 M ) = 0.05 M , $\Delta$ Zn ²⁺ = 0.485 - 0.405 = 0.08

At an ionic strength of 0.083 M , we get

$\Delta$$\mu$ = ( 0.100 M - 0.083 M ) = 0.017 M

$\Delta$ Zn ²⁺ = (0.017 / 0.05 ) $\times$ 0.08 = 0.0272

Therefore, $\Delta$ Zn ²⁺ = 0.405 + 0.0272 = 0.432

ANSWER : $\Delta$ Zn ²⁺ = 0.432