Conductivity in Solutions

Question 1

Ohm’s Law

Answer 1

V = I x R
V = potential difference (V; volt)
I = current (A; Ampere)
R = Resistance (W; ohm)

Question 2

Conductance

Answer 2

G = 1/R
measured in Siemens (S)

Question 3

Conductivity

Answer 3

k = G x L/A
k is (S m^-1)
L is the physical distance

Question 4

What type of solutions can conduct an electrical charge?

Answer 4

Ionic Solutions (electrolytes)
* charged species (ions: cations, anions) migrate towards electrodes, conducting a current

Question 5

What charge are cations and towards which electrode do they migrate?

Answer 5

Positively charged, migrate towards cathode (negatively charged)

Question 6

What charge are anions and towards which electrode do they migrate?

Answer 6

Negatively charged, migrate towards anode (positively charged)

Question 7

What does conductivity (k) depend on?

Answer 7

• on concentration (c) - the more ions in solution the more charge they can move.
• also depends on the electrolyte used and how they dissociate in solution (electrolytes can have varying strengths (strong, intermediate and weak)

Question 8

Types of Electrolytes

Answer 8

1:1 - made up of single charge ions

2:1 - made up of single and double charged ions

2:2 - made up of double charged ions

3:2 - triple charged and double charged (e.g., 3+ and 2-)

Question 9

Molar Conductivity (A without middle line)

Answer 9

is the conductivity of electrolyte when dissolved in solution:
A = k/c
molar conductivity = conductivity/concentration

Question 10

Sum of the anionic and cationic contributions from an electrolyte

Answer 10

In general for a x:y electrolyte:
AyBx

Question 11

What is Ionic Pairing?

Answer 11

• Ion pairing means the ions have no net charge, so
  they won’t migrate towards an electrode, thus
  affecting conductivity.
• The ions can also be attracted to each other
  temporarily through electrostatic force, creating an
  ‘ion pair’.