Electroplating - Electrochemistry, Class 12 Video Lecture

hi everybody my name is Paula spencerian
and this is chem class today we be in a
series of videos on electrochemistry I'd
like to begin with a quick demonstration
the demonstration is a single
displacement reaction between silver
nitrate and solid copper when i place
the solid copper into solution it
displaces the silver that's in solution
as you can see the silver is
precipitated out and is collecting on
the copper wire at the same time copper
is replacing silver in solution as a
cation with a plus two charge this
cation has a characteristic color of
blue in solution the electron transfer
theory is used to explain how and why
electrochemical reactions occur what
we're seeing is a transfer of electrons
from the copper to the silver cations in
solution what this does is allows the
car the silver to neutralize its charge
and collect a solid silver on the copper
wire at the same time the copper atoms
are replacing the silver in solution as
a cation
the chemical equation shows all
substances present in solution however
it does not show how the electrons are
transferred from the chemical equation
we can form two half reactions that show
which substance loses electrons and
which substance gains electrons note
that the nitrate anion in this example
neither gains nor loses electrons it is
present to balance the charge of the
solution but does not take part in the
electron transfer process we call this
type of ion a spectator ion the loss of
electron is called an oxidation while
the gain of an electron is called a
reduction by multiplying the molar
coefficients of the half reactions we
can balance the number of electrons lost
to the number of electrons gained this
leaves no electrons unaccounted for the
sum of the two half-reactions is called
the net ionic equation it only shows the
substances that are oxidized and reduced
so to recap the electron transfer Theory
describes the transfer of electrons as a
possible mechanism for electrochemical
reactions the substances that lose
electrons are oxidized while the
substances that gain electrons are
reduced balancing the electrons lost and
gained in the half reactions yield the
sum of these equations called the net
ionic equation electrochemical reactions
are also known as redox reactions
because substances are being reduced
while others are oxidized we can
remember the definition of oxidation and
reduction using a simple memory aid leo
the lion says durer a loss of electrons
means the substance is oxidized while a
gain of electrons means the substance is
reduced that's all the time we have
today thanks for joining us here in chem
class