revision topic 5 Flashcards
what is the meaning of Electrolysis
it’s the breaking down using electricity, where an electric current is used to break down an ionic substance called an electrolytes
what is the positive electrode?
anode
what is the negative electrode
cathode
what happens during electrolysis in terms of ions
positively charged ions go to the cathode and negatively charged ions go to the anode
in electrolysis, the ions in the anode are always?
oxidized to become balanced i.e neutral
in electrolysis, the ions in the cathode are always?
reduced to become balanced i.e neutral
in a solution what is the rule for the element forming at the cathode
hydrogen is always formed in the cathode unless there is a less reactive positive ion there
in a solution what is the rule for the element forming at the anode
oxygen is always formed in the anode unless there is a halogen present
what is the half equation for hydroxide ions
4OH- ——-> 2H2O + O2 + 4e-
from what ore is Aluminium extracted from
bauxite
what’s the problem with electrolyzing Aluminum ore and how do we solve it
it has a high melting point so it requires a lot of energy to break to avoid that we would use motel cryolite as a catalyst to lower the melting point
in aluminum electrolysis what is formed in the cathode and its half equation
Aluminum is formed and its half equation is:
Al3+ ———-> Al - 3e-
in aluminum electrolysis what is formed in the anode and its half equation
oxygen is formed and its half equation is:
2O2- ——> O2 + 4e-
what are the 3 useful products formed in the electrolysis of brine
chlorine gas, hydrogen gas, and sodium hydroxide solution
in the electrolysis of brine what is formed in the cathode and the half equation
hydrogen gas and it’s half equation is:
H2+ ——> 2H - 2e-
in the electrolysis of brine what is formed in the anode and the half equations
chlorine solution and it’s half equation is:
Cl2- ——> 2CL + 2e-
how can you extract a sodium hydroxide from brine electrolysis?
at the cathode when hydrogen gets extracted from the hydrogen it leaves hydroxide ions which react with sodium to form sodium hydroxide, in order to prevent the mixture of sodium chloride and sodium hydroxide a porous membrane is used to separate the cathode and the anode extracting the pure sodium hydroxide
how can we use chlorine
by making bleach which is made by reacting
how can we use hydrogen
by making margarine which is made by reacting hydrogens with vegetable oil
how can we use sodium hydroxide
by making soup, paper, and bleach
what is an electroplated object
It an objected coated by a thin layer of metal by electrolysis
why would we electroplate an object
- to protect the metal beneath from corroding
- to make an object look more attractive
- to in the hardness of the surface and its resistance to scratching
- to save money by making cheaper jewelry
how does electroplating work
the metal object to be plated is used as the cathode and the plating metal is put in the anode, so the ions from the plating metal would go to the negative cathode plating the mental that’s was placed there
what is the half equation that happens in the anode in an electroplating
product then reactants
what is the half equation that happens in the cathode in the electroplating
reactants then products
what are inert electrodes
they are electrodes that dont take place in electrolysis for example carbon metal electrodes
what are active electrodes
they are electrodes that take place in electrolysis for example metal electrodes
when using active electrodes what happens to the electrodes
the anode would lose mass since the ions in it are positive so they would go to the cathode making the cathode gain mass hence:
the loss in mass of active electrode at the anode = the gain in mass of active electrode at the cathode
