ELECTROLYSIS -- 5.4.3.5 Reactions at electrodes as half equations Flashcards
(17 cards)
What are half equations?
Half-equations show what happens to ions at each electrode during electrolysis and balance the charge by showing electrons gained or lost.
What occurs at the cathode (-) during electrolysis?
Positive ions gain electrons (Reduction).
What is the mnemonic to remember the processes of oxidation and reduction?
OIL → Oxidation Is Loss
RIG → Reduction Is Gain (of electrons).
What happens to positive metal or hydrogen ions at the cathode?
They gain electrons in a reduction reaction.
Write the half-equation for the formation of hydrogen gas (H₂) from H⁺ ions.
2H⁺ + 2e⁻ → H₂
What is the half-equation for the formation of copper metal (Cu) from Cu²⁺ ions?
Cu²⁺ + 2e⁻ → Cu
What occurs at the anode (+) during electrolysis?
Negative ions lose electrons (Oxidation).
Write the half-equation for the formation of oxygen gas (O₂) from OH⁻ ions.
4OH⁻ → O₂ + 2H₂O + 4e⁻
What is the half-equation for the formation of chlorine gas (Cl₂) from Cl⁻ ions?
2Cl⁻ → Cl₂ + 2e⁻
What is the key rule for balancing half equations?
Make sure the total charge is balanced on both sides.
What is the example of the electrolysis of water (H₂O) at the cathode?
2H⁺ + 2e⁻ → H₂
What is the example of the electrolysis of water (H₂O) at the anode?
4OH⁻ → O₂ + 2H₂O + 4e⁻
True or False: At the cathode (-), electrons are added to the right (products) for reduction.
False
True or False: At the anode (+), the number of electrons lost must equal the number of electrons gained.
True
Fill in the blank: At the cathode (-), electrons are added to the ______ for reduction.
left (reactants)
Fill in the blank: At the anode (+), electrons are added to the ______ for oxidation.
right (products)
What should you learn regarding common half-equations?
Learn common half-equations like hydrogen, oxygen, chlorine, and copper.
