Chapter 13 electrochemistry Flashcards
what electrode is connected to the positive terminal
anode
What are anodes?
Anions lose electrons to form anode and become oxidised
- Forms molecules
ex 2x- -> x2 + 2-e-
What are cathodes
Gain electron to form cations and become reduced
ex: Na+ + e- -> Na
Examples of inert electrode
Platnium carbon and graphite
Examples of non electrolyte
does not allow electricity to pass through
ex : sugar distileld water and ethanol
Advnatage of graphite
High mp
will not melt in molten compounds
Disadvantage of graphite
Graphite reacts with oxygen
Under high temp to produce carbon dioxide
- needs to be replaced periodically
Advantage of platnium
Does not participate in electrolysis reaction
Disadvantage of platnium
Lower mp than graphite
Melt in molten
Used in aqueous
method and effect of conduction of metals
Flow of electrons from one end to another
Chemically unchanged
Electrolyte conduction by electrolytes
Method and effect
Movement of ions across molten
Electrolyte decomposed to form new substances
Half equation for molten sodium chloride
Cathode: Na
Anode: chloride
What will never be discharged in concentrated ion
Sundays and nitrate ions
Equation of oh- ions in anode
And overall equation of h + oh-
4Oh- (aq) ->2h2o + o2 + 4e-
What happens to more reactive metal in electrolyte
More reactive is preferentially oxidised ( anode )
At positive terminal
What affects the voltage
Further apart in metallic series, greater voltage produced
Advantage of using hydrogen as fuel
renewable source of energy as hydrogen is obtained from electrolysis of water
Hydrogen fuel cells produce water
as the only product of combustion
of hydrogen. Water has no
adverse effect (harmless) to
human health.
2H2(g) + O2(g) → 2H2O
Hydrogen is more efficient source
of energy, which provides more
than twice the amount of energy
compared to many other fuels.
A larger percentage of the
chemical energy stored in the fuel
ends up as useful electricity in a
Disadvantages of using hydrogen as a fuel
It is difficult to find a cheap source of
hydrogen. Obtaining hydrogen from
electrolysis is an expensive process.
- Hydrogen is currently obtained from non-
renewable energy sources such as cracking
petroleum.
* It is difficult to store and transport hydrogen
safely as hydrogen is a highly flammable
gas at room temperature and pressure.
Hydrogen is often transported in high-
pressure cylinders which can be dangerous
to handle.
* Hydrogen is very light and is a gas at room
temperature, and thus requires larger
storage volumes compared to other fuels.
* storage of fuel requires pressurised tank
which might be costly / explosive / need to
store under high pressure
* Processes involved in obtaining
hydrogen from cracking petroleum and
electrolysis of water will require the
burning of fossil fuels which release
pollutants such as CO2, CO and SO2.
* A large amount of energy is needed to
produce hydrogen from electrolysis.
**However, this can be mitigated by using
renewable sources like solar and wind
energy to power electrolysis.
