C5 - Electricity and chemistry Flashcards
PANIC
Positive is Anode, Negative Is Cathode
What is electrolysis
the process of splitting an ionic compound when molten or aqueous solution by the passage of electricity
When ionic compounds are melted or dissolved in water the ions are
free to move around in the solution
What is an electrode
rod that conducts electricity (they come in pairs of Pos and neg)
What is a electrolyte
ionic compounds dissolved in water to make a solution that conducts electricity
How do we distinguish a difference between electrolytes and non-electrolytes
By using a complete circuit which shows whether a light bulb will glow or not.
Electrolytes will make the light bulb glow
Non-electrolytes will do nothing
When a voltage (d.c) is applied across an electrolyte where do the charged ions go
Oppositely attract
Positive ions go to negative electrode (cathode)
Negative ions go to positive electrode (anode)
When an ion touches an electrode electrons can be
transferred to form elements.
E.g if Cu2+ ions in a solution move to the cathode due to voltage applied, when they touch the cathode each Cu2+ will gain 2 electrons and form a copper metal
How can ionic compounds under go electrolysis
When ionic compounds are dissolved in a solution or turned molten the ions are free to move.
The solution can then conduct electricity and will attract to a certain electrode.
If copper ions (Cu2+) are in a solution and a voltage is applied, which electrode will they move towards and what will happen when they touch that electrode?
When a voltage is applied across an electrolyte, the charged ions are attracted to the oppositely charged electrodes.
Copper ions (Cu2+) are positively charged, so will move towards the cathode (negative electrode).
When the copper ions (Cu2+) touch the cathode, each ion will gain 2 electrons, forming copper metal:
Cu2+(aq) + 2e- → Cu(s)
What substance are electrodes made out of and why
Usually made out of carbon or platinum as they are inert meaning they won’t undergo the chemical change during electrolysis.
Describe what happens during the electrolysis of molten lead bromide
When PbBr2 is melted the ions are free to move.
The voltage is applied and the positive lead ions move to the cathode
The negative bromide ions move to the anode
The products of the electrolysis are the elements bromine and lead as the ions gain or loss their electrons to form elements.
Silvery deposits of lead form near the cathode and brown bromine vapor form near the anode to show electrolysis occurred.
What are the half equations of electrolysis of molten lead bromide
Pb2+ + 2e- ==> Pb
2Br- ==> Br2 + 2e-
Electrolysis of Aqueous solutions
Water molecules in the solution split up to form H+ ions and OH- ions.
What is formed at the cathode:
If the metal is more reactive than hydrogen, hydrogen is produced.
If the metal is less reactive than hydrogen, the metal is produced.
What is formed at the anode:
If halide ions are present, the halogens form
If halide ions are absent, oxygen forms
Electrolysis of sodium chloride solution NaCl
Ionic compound NaCl dissolves in water.
Sodium and chloride ions separate and are free to move.
Hydrogen and hydroxide ions also are free to move separated from the water.
Sodium is more reactive than hydrogen so, hydrogen ions are discharged and form as molecules at the cathode. The sodium ions stay in the solution
Since there is a presence of a halide ion (chloride), chlorine ions discharge and form chlorine molecules at the anode. OH- ions stay in the solution
BaCl ==> Na+ + Cl-
H2O <==> H+ + OH-
What is dissociation
the process in which water breaks up and forms ions