Electrolysis - Topic 3 - Paper 1
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What type of ions do metals typically form?
Cations
What type of ions do non-metals usually form?
Anions
Define Cation
Positively charged ion
Define Anion
Negatively charged ion
How is a cation formed?
An atom loses electrons, becoming positive, to obtain a full outer shell (typically metals)
How is an anion formed?
An atom gains electrons, becoming negative, to obtain a full outer shell (typically non-metals)
Define Ion
Electrically charged particle formed when an atom or molecule gains or loses electrons
Define charge
Property of matter that causes a force when near another charge
Describe the structure of a cation in terms of subatomic particles
More protons than electrons Full outer shell of electrons
In the electrolysis of aqueous solutions, what is the rule for determining which ion will be reduced (gain electrons) at the cathode (negative electrode)?
Always be the H+ ion, unless Cu2+ is present Always the ion of the least reactive element Copper is the only metal (in the reactivity series that we learn anyways) above less reactive that hydrogen - further down the reactivity series than hydrogen Please - Potassium Stop - Sodium Like - Lithium Calling - Calcium Me - Magnesium A - Aluminium Careless - Carbon Zebra - Zinc It’s - Iron Tiring - Tin Look - Lead How - Hydrogen Can - Copper Shiven - Silver Go - Gold Platinum
In electrolysis, which direction do the electrons travel?
Anode ➔ Cathode Positive to negative - the direction of conventional current
In the electrolysis of aqueous sodium chloride, NaCl (aq), which four ions would be present in the electrolyte?
Sodium ions (Na+) Chloride ions (Cl-) Hydrogen ions (H+) Hydroxide ions (OH-)
In the electrolysis of aqueous sodium chloride, NaCl (aq), which of the four ions will be reduced at the cathode (negative electrode)?
H+ The rule is that it will always be the H+ ion, unless Cu2+ is present - always the atom of the least reactive element - all metals are above Hydrogen in the reactivity series apart from copper (and the inert silver, gold and platinum) In this case the positive ions are H+ and Na+, so it will be the H+ which is reduced.