C6- electrolysis 💧 Flashcards
What is electrolysis ? [3]
Hint: compounds
- electrolysis, is the chemical effect of electricity
- on ionic compounds,
- causing them to break up into simpler substances [usually elements]
What is the anode ?
Hint: what’s it connected to?
- the anode, is the positive electrode that is connected to the positive of the battery.
What is the cathode ?
- the cathode, is the negative electrode, that is connected to the negative of the battery
What is an electrode ? [4]
Hint: electricity passes
- an electrode, is a metal rod that is placed in the liquid; through which electricity passes.
- electrodes, can be made be out of carbon [graphite],
- platinum and copper etc.
What is the mnemonic, to remember which electrode is positive and negative ?
- PANIC- positive is anode, negative is cathode.
What is the electrolyte ? [4]
Hint: aqueous, what passes?
- the electrolyte, is a [aqeous] solution
- or molten solid [liquid] of an ionic substance
- , through which the electrical current passes.
- The mass of this ionic substance will decrease during electrolysis, as it is split up.
RECAP: What’s an ionic substance ? [4]
Hint: held together by bonds
- an ionic substance, is a compound that is held together by ionic bonds.
- ; Ionic bonds are created when one element [usually a metal] loses an electron to a non metal.
What is the first key fact about electrolysis? [4]
- solid ionic compounds can’t be electrolysed
- This is because the ions are locked in place,
- due to being held by strong electrostatic forces of attraction
- and therefore, they’re not free to move.
Explain why electrolysis can only occur when an ionic compound is molten or in aqueous solution.
Hint: ions
- solid ionic compounds can’t be electrolysed
- ; when an ionic compound is melted or dissolved in water, the forces of attraction are broken, and the ions are free to move.
- therefore, when an ionic compound is melted or dissolved in water [molten/liquid], they can be electrolysed and conduct electricity.
- [scientists call these liquid or solution electrolytes]
Why do ions become atoms at the electrodes, during electrolysis ⚛️ [5]
Hint: form, positive- gain 🆚️ negative
- during electrolysis, ions become atoms at the electrodes:
- because positive metal ions are attracted to the negative electrode,
where they gain electrons and form metal atoms [cation] - ; negative non-metal ions are attracted to the positive electrode,
where they lose electrons and form non-metal atoms [anions]
What’s the difference between the electrical charge carried through wires 🆚 the electrical charge carried though electrolyte ? [5]
Hint: electrons- why?, number dosen’t equal
- in the electrical charge carried through wires, the electrical charge is carried by electrons.
- This is because, electrons have a negative charge
- due to their behavior in an electric field.
- ; the electrical charge carried though electrolyte, is carried by ions
- because, the number of electrons don’t equal the number of protons in the atom or molecule
What ions do lead bromide contain ?
- lead bromide, contains two ions: the positive lead ion and the negative bromide ion.
What can you tell me about the general idea of the electrodes, in electrolysis ?
Hint: lack of/covered with
Hint #2: conducting material
- in electrolysis, there are two electrodes made of a conducting material [graphite or a metal].
- the negative electrode is known as the cathode, and is attached to the negative terminal of a power pack. [it’s covered with electrodes from the power pack]
- ; the positive electrode, is called the anode and is connected to the positive terminal of the power pack. [it has a lack of electrons]
Briefly explain what happens when we carry out electrolysis, on lead bromide
- the positive lead ions are attracted to the negative electrode because, opposite charges attract.
- ; the negative bromide ion, is attracted to the positive electrode.
What happens when we carry out electrolysis on a molten [melted] ionic compound? [lead bromide]
Hint: gain/lose
- the positive lead ions are attracted to the negative electrode because, opposite charges attract.
- The lead ion will now gain two electrons, to form lead atoms and this is a reduction reaction [as it gains electrons]
- ; the negative bromide ion, is attracted to the positive electrode.
- The negative bromide ion, will lose one electron to form bromide atoms and this is an oxidation reaction [as it loses electrons].
What can you tell me about bromide atoms ?
Hint: pair
- bromide atoms will pair to form a bromide molecule
Why do opposites attract [and like charges repel] ? ❤️
Hint: charged ion
- opposites attract [and like charges repel] because matter wants to possess neutral state.
- a negatively charged ion wants to give away its electrons to become neutral therefore it attracts positive charge towards it.
- ; a positively charged ion requires electrons to become neutral, that is why it moves towards negative charge.
Why do like charges repel] ? 🫸
Hint: place a negative charged particle
- opposites charges attract [and like charges repel] because matter wants to possess neutral state.
Why must the electrolyte be a liquid ?
- the electrolyte must be a liquid, so the ions are free to move to the electrodes
Why do ions move in the electrolyte ?
Hint: cation 🆚️ anion
- ions move in the electrolyte because, opposite charges attract.
- positive ions [cations] are attracted to the negative cathode.
- and negative ions [anions] are attracted to the positive anode.
What is the difference between a cation 🆚 an anion ?
Hint: attracted
- cations, are positive ions that are attracted to the negative cathode.
- ; anions are negative ions that are attracted to the positive anode.
What’s a word equation, to describe the electrolysis of a molten ionic compound
Hint: lead bromide
- the word equation, to show the electrolysis of molten lead bromide is:
- PbBr2( l ) Lead bromide ⟶ Pb ( s ) Lead + Br 2 ( g ) Bromine gas .
- the products are lead bromine gas; the reactants is lead bromide.
Why can electrolysis be described in terms of the movement of ions ?
Hint: electric current, electrolyte, move
- electrolysis can be described in terms of the movement of ions:
- This is because, passing an electric current through electrolytes, causes the ions to move to the electrodes
- as the free moving ions in electrolytes, are attracted to the oppositely charged electrodes- that are connected to the dc supply
When writing half-equations, what is the tip you must remember ?
- when writing half -equations, if there is a positively charged ion, the electron goes before the arrow to balance the charges
