DAILY QUESTIONS
• Circle the oxidized element, underline the reduced
element.
2Sr +O2 2SrO
Fe+2 +O2 FeO
• Define what happens to elements that are oxidized and
reduced.
OBJECTIVES:
C5.1 State that electrolysis is the chemical effect of electricity on ionic
compounds, causing them to break up into simpler substances, usually
elements
C5.2 Use the terms electrode, electrolyte, anode and cathode
C5.4 Describe the electrode products, using inert electrodes, in the
electrolysis of:
• molten lead bromide
• aqueous copper chloride
• dilute sulfuric acid
ELECTROLYSIS APPARATUS
Electrode - an
electrical conductor
which carries charge
to or from a liquid
undergoing
electrolysis.
Electrode
Electrode
Electrolyte - a molten
or aqueous solution
through which an
Electrolyte
electrical current can
flow.
ELECTROLYSIS APPARATUS
Anode:
The positively charged
electrode. Attracts negatively
charged ions (anions).
Anode
+
-
Cathode:
The negatively charged
electrode. Attracts positively
charged ions (cations).
Cathode
Electrolyte
• Electrolysis only happens in:
- molten ionic liquids or
- aqueous solutions containing ions.
• There must be a complete circuit.
• A lamp or ammeter can be used to
show that electricity is flowing
around the circuit.
ELECTROLYSIS OF ZINC CHLORIDE
In your journal:
Describe what is
occurring during
the electrolysis of
zinc chloride.
ELECTROLYSIS
• Introducing electricity to a mixture can cause a
chemical reaction to occur.
• However, this requires that the atoms involved
become ions
• Define ions
FORMING IONS
Na
Cl
FORMING IONS
Na
Cl
Na+
Cl-
BONDING
The outer shell is full, but the ions are not
neutral. How can neutrality be achieved?
Na+
Cl-
IONIC BONDING
An ionic bond is a strong
electrostatic force of attraction
between oppositely charged
ions
[Na]+ [Cl]-
LET’S TRY A FEW
• Lithium & Fluorine
• Magnesium & Fluorine
CONDUCTIVITY
Conductivity is the ability of a substance to
conduct electricity.
For a substance to conduct electricity,
“free” electrons have to be available
Free electrons = electrons that are able to
move
CONDUCTIVITY IN METALS
•
•
•
•
Electrons move
Metals can be in solid or liquid form
No chemical change takes place
Examples: copper wire; aluminum pan
CONDUCTIVITY IN IONIC COMPOUNDS
• Ions move
• Ionic compounds can be in liquid (molten)
form or in aqueous solution
• Chemical change takes place
• Examples: molten lead bromide, sodium
chloride solution, copper(II)sulfate solution
AT THE ELECTRODES
Cathode (-)
(negative electrode)
Positive ions go here
(cations).
As metal ions are positive,
they go to the cathode.
Ions gain electrons. They are
reduced and become
neutral atoms.
Anode (+)
(positive electrode)
Negative ions go here (anions).
As non-metal ions are
negative, they go to the
anode.
Ions lose electrons. They are
oxidised and become neutral
atoms
(which react together to
form molecules).
ELECTROLYSIS OF COPPER CHLORIDE
In your journal:
For the electrolysis of copper
chloride:
1. Identify the ions present
in the electrolyte.
2. Describe the movement
of ions.
+
Electrolyte:
CuCl2 (aq)
ELECTROLYSIS OF SOLUTIONS – CATHODE
For solutions of highly reactive
metals: Hydrogen gas, not the
metal, is produced at the
cathode.
For metals that are more reactive
than hydrogen, the metal will stay
in the solution and hydrogen gas
will be produced.
ELECTROLYSIS OF SOLUTION - CATHODE
ELECTROLYSIS OF SOLUTIONS-ANODE
The product at
the anode depends on:
The negative anions
present in the solution.
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•
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Homework:
Read the lab report
Grade based on the
rubric provided
Missing CourseworkCome in Thursday
Missing homework- fill
form then turn in.