A2: Electrochemical Cells Flashcards
One essential property of the porous separator?
- unreactive 🙅
* allows IONS to pass 🏃 through it
Function of the electrode?
allow transfer of ELECTRONS
Why might the recharging of a lithium cell lead to release of carbon dioxide?
ELECTRICITY for recharging the cell
comes from power stations
🔥 burning fossil fuels
SALT BRIDGE 🌉
- MOBILE 📲 ions!!!
* provides an ELECTRICAL 💤 connection between two electrodes
Direction of ELECTRON flow through the WIRE?
from the MOST REACTIVE metal —> to the LEAST
Out of Zinc and Copper, which gets oxidised and which gets reduced?
oxZidised = Zinc reduced = Copper
in the Fe2+/Fe3+ conversion, what’s the electrode made out of?
PLATINUM bcos it’s INERT
WHY are standard conditions used to measure Electrode Potentials?
ensures you always get the SAME VALUE for the ELECTRODE POTENTIAL so you can COMPARE VALUES for different cells
Name the standard reference electrode against which all other electrode potentials are measured
Standard hydrogen electrode
what ARE the standard conditions?
298 K and Concentrations at 1 mol dm–3
What is the value of the electrode potential of the Standard hydrogen electrode
0 ZERO V
Identify a secondary standard electrode and give a reason why it is used rather than a standard hydrogen electrode
Ag
Easier to use
More reactive METALS have more _______ standard electrode potentials:
NEGATIVE
More reactive NON-METALS have more _______ standard electrode potentials:
POSITIVE
Why is it impractical to reverse a Zinc-Carbon DRY CELL battery? (2 marks)
- since the ZINC ANODE forms casing of the battery, as it becomes oxidised, casing becomes THINNER so battery can leak/explode
- the ammonium ions produce Hydrogen GAS which escapes from the battery
2 examples of a rechargeable battery?
- NiCad (Nickel-Cadmium) and Lithium ion
How are rechargeable batteries recharged?
a CURRENT is SUPPLIED to force ELECTRONS to flow in the OPPOSITE DIRECTION around the circuit and REVERSE the REACTION. This is possible bcos none of the substances ESCAPE or are USED UP.
+/- of NON-rechargeable batteries? (4 marks)
- Cheaper BUT more frequently REPLACED
- Will work for longer than a rechargeable battery but once it runs out, you can’t recharge it
(-) Non-rechargeable produced more often to creates more waste - landfill
(+) Non-rechargeables less likely to contain TOXIC metals e.g. Cadmium so LESS HAZARDOUS in LANDFILL if contents LEAKS out and POLLUTES water
