Question

Consider an aqueous solution of HCl and Ca(NO₃)₂ with the following concentrations: [HCl] = 0.30 M, [Ca(NO₃)₂] = 0.10 M.

(a) Calculate the conductivity of this solution at 25 ^oC.
(b) Calculate the resistance of a cylinder of this solution with the diameter of 2.0 cm and the length of 10 cm. Electrodes are located at the opposite ends of the cylinder.

Answer 1

there is no direc relation between conductivity and concentration , we can just estimate whether it will increase or decrease with concentraion.

thus i used literature value of m for the solutes and also i assumed teh volume is 1000 l after addition.

m = (1000 X k )/ C

375.9 = (1000 X k)/ 0.3

0.1127 S

and for Ca(NO₃)₂

m =262  =1000 X k/C

k= 0.0262 S

thus total conductivity = k_HCl + k_Ca(NO3)2

=0.1389 S

b

R= l/a

= 1/k

thus = 7.2 Ω⋅cm

or

Area=2πrh+2πr²

thus substituting values

area of cylinder = 69.08 cm²

R = 7.2 X 10/69.08

1.042 Ω