Conductivity of Electrolytes

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Page ID: 128802

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Required Training	Required PPE
UC Lab Safety Fundamentals	Lab coat, safety glasses/goggles, nitrile gloves

Equipment	Chemicals
Conductivity apparatus with light bulb (7.5 W, 110V	100ml 1 M Hydrochloric acid
7 150 mL beakers labeled	100ml 1 M Sodium hydroxide
DI water squirt bottle	100ml 1 M Sodium chloride
Kimwipes	100ml 1 M Acetic acid
Ring stand	100ml 1 M Ammonium hydroxide
	100ml DI water
	100ml Tap water

Procedure:

Ensure the light bulb is not burnt out by inspecting the filament.
Wash with DI water and test the conductivity apparatus before each use before an audience.
Submerge the electrode of the conductivity apparatus fully into the DI beaker first (the wires within the yellow safety covers are about 3 cm further back)
Wash the apparatus with DI water after each beaker to avoid contamination, especially with the two water samples

Discussion:

This demonstration shows the effects of electrolytes on a solution’s conductivity. Although this demonstration only shows a qualitative difference, the brightness can be differentiated between acetic and hydrochloric acids, etc. The theory behind this demonstration is as follows. Ions are atoms or molecules which have gained or lost an electron. In liquids, these molecules are free to move around. Negative ions are attracted to the positive electrode, while positive ions are attracted to the negative electrode. This flow of ions (electrons) is what completes the circuit and allows the AC power to light the light bulb.

Hazards:

DO NOT TOUCH THE LIQUID WHILE THE CONDUCTIVITY APPARATUS IS IN PLACE. SHOCK HAZARD. This demo is wired such that the 110v AC does not come into contact with the solution. Advise students not to try this at home, and use caution when dealing with electrical phenomena. Wear all appropriate safety PPE when dealing with acids and bases.

SOP:

Corrosive – Ammonium Hydroxide, Hydrochloric Acid, Sodium Hydroxide

Disposal (by Storeroom)

Return the demonstration setup to the storeroom after rinsing the conductivity apparatus’ probes with DI water.