Chapter 13 electrochemistry

Question 1

what electrode is connected to the positive terminal

Answer 1

anode

Question 2

What are anodes?

Answer 2

Anions lose electrons to form anode and become oxidised
- Forms molecules
ex 2x- -> x2 + 2-e-

Question 3

What are cathodes

Answer 3

Gain electron to form cations and become reduced
ex: Na+ + e- -> Na

Question 4

Examples of inert electrode

Answer 4

Platnium carbon and graphite

Question 5

Examples of non electrolyte

Answer 5

does not allow electricity to pass through
ex : sugar distileld water and ethanol

Question 6

Advnatage of graphite

Answer 6

High mp
will not melt in molten compounds

Question 7

Disadvantage of graphite

Answer 7

Graphite reacts with oxygen
Under high temp to produce carbon dioxide
- needs to be replaced periodically

Question 8

Advantage of platnium

Answer 8

Does not participate in electrolysis reaction

Question 9

Disadvantage of platnium

Answer 9

Lower mp than graphite
Melt in molten
Used in aqueous

Question 10

method and effect of conduction of metals

Answer 10

Flow of electrons from one end to another
Chemically unchanged

Question 11

Electrolyte conduction by electrolytes
Method and effect

Answer 11

Movement of ions across molten
Electrolyte decomposed to form new substances

Question 12

Half equation for molten sodium chloride

Answer 12

Cathode: Na
Anode: chloride

Question 13

What will never be discharged in concentrated ion

Answer 13

Sundays and nitrate ions

Question 14

Equation of oh- ions in anode
And overall equation of h + oh-

Answer 14

4Oh- (aq) ->2h2o + o2 + 4e-

Question 15

What happens to more reactive metal in electrolyte

Answer 15

More reactive is preferentially oxidised ( anode )
At positive terminal

Question 16

What affects the voltage

Answer 16

Further apart in metallic series, greater voltage produced

Question 17

Advantage of using hydrogen as fuel

Answer 17

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

Question 18

Disadvantages of using hydrogen as a fuel

Answer 18

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.