Question

Conductivities are often measured by comparing the resistance of a cell filled with the sample to its resistance when filled with some standard solution,such as aqueous potassium chloride. The conductivity of water is 76 mS m^(-1) at 25 C and the conductivity of 0.100 mol dm^(-3) KCl (aq) is 1.1639 S m^(-1) A cell has a resistance of 33.21ohm when filled with 0.100 mol dm^(-3) KCl (aq) and 300.0 ohm when filled with 0.100 mol dm CHaCOOH (aq). What is the molar conductivity of acetic acid at that concentration and temperature?

Answer 1

1200 Sm^2mol^-1

Step-by-step explanation:

Given data :

conductivity of water ( kwater ) = 76 mS m^-1 = 0.076 Sm^-1

conductivity of kcl (aq)( Kkcl ) = 1.1639 Sm^-1

Kkcl = 1.1639 - 0.076 = 1.0879 Sm^-1

Resistance = 33.21 Ω

where conductivity can be expressed as =
`(Cell constant)/(Resistance )`

hence cell constant = conductivity * Resistance

= 1.0879 * 33.21 = 36.13m^-1

conductivity of CH3COOH ( kCH3COOH ) = 36.13 / 300

= 0.120 Sm^-1

Determine the molar conductivity of acetic acid

= ( kCH3COOH * 1000 ) / C

C = 0.1 mol dm

= (0.120 * 1000) / 0.1 = 1200 Sm^2mol^-1