Is the Positive Electrode the Cathode and Negative Electrode the Anode? Watch

ΘTheta
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So is a positive electrode where Oxidation occurs to produce positive ions which make the solution positive, and the negative electrode where reduction occurs, and so the ions react with the electrons from the oxidation cell, hence meaning that there are less positive ions in the solution, as more ions are being reduced by the electrons from the oxidation cell?

Thanks guys! =)
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JamesRobertson
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Anode = Negative Terminal, Cathode = Positive Terminal
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JasonBrown2K14
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Good way of remembering it:

P - Positive
A - Anode
N - Negative
I - is
C - Cathode

PANIC!


And then for oxidisation and reduction:

O - Oxidisation
I - is
L - lost
R - Reduction
I - is
G - gained

OIL RIG.
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Pigster
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It actually depends on whether you're making electricity or using electricity.
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ΘTheta
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What happens at the negative terminal and positive terminal?
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charco
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(Original post by ΘTheta)
What happens at the negative terminal and positive terminal?
of what?

an electrolytic cell or an electrochemical cell?

In an electrolytic cell the negative electrode (cathode) provides electrons and causes reduction of positive ions.

In an electrochemical cell the negative electrode (anode) sends electrons around the external circuit by oxidation of the metal ions in the electrode.
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ΘTheta
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(Original post by charco)
of what?

an electrolytic cell or an electrochemical cell?

In an electrolytic cell the negative electrode (cathode) provides electrons and causes reduction of positive ions.

In an electrochemical cell the negative electrode (anode) sends electrons around the external circuit by oxidation of the metal ions in the electrode.
I meant in an electrochemical cell. Thanks!
So do the electrons made by the oxidation at the anode, move via the wires through the voltmeter to the cathode where reduction takes place?
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charco
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(Original post by ΘTheta)
I meant in an electrochemical cell. Thanks!
So do the electrons made by the oxidation at the anode, move via the wires through the voltmeter to the cathode where reduction takes place?
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ΘTheta
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(Original post by charco)
Thanks Again.
The voltmeter measures potential difference, what does this mean?
And why does the voltmeter need to be be infinite resistant?
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mphysical
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(Original post by ΘTheta)
Thanks Again.
The voltmeter measures potential difference, what does this mean?
Difference in voltage across two points in a circuit.

And why does the voltmeter need to be be infinite resistant?
A voltmeter contains a large known value resistor across which the p.d. is measured.
This ensures only a small current flows through the sensitive circuitry.
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Plato's Trousers
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(Original post by charco)
of what?

an electrolytic cell or an electrochemical cell?

In an electrolytic cell the negative electrode (cathode) provides electrons and causes reduction of positive ions.

In an electrochemical cell the negative electrode (anode) sends electrons around the external circuit by oxidation of the metal ions in the electrode.
This is kind of annoying, right? (and is a fact that seems to have slipped by me un-noticed throughout my A levels and degree!)

So if it's not the polarity that gives the anode and cathode their name, what is it?
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ΘTheta
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(Original post by mphysical)
The voltmeter measures potential difference, what does this mean?
Difference in voltage across two points in a circuit.

And why does the voltmeter need to be be infinite resistant?
A voltmeter contains a large known value resistor across which the p.d. is measured.
This ensures only a small current flows through the sensitive circuitry.
But here is what I don't understand though, if the electrons are made by the oxidation at the anode, which flow through the wires, is that not reducing the voltage as there is a current (flow of electrons) flowing through the voltmeter? :confused::confused::confused::confused:
Thanks
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charco
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(Original post by Plato's Trousers)
This is kind of annoying, right? (and is a fact that seems to have slipped by me un-noticed throughout my A levels and degree!)

So if it's not the polarity that gives the anode and cathode their name, what is it?
I don't know the derivation of the terms, but I imagine that we are dealing with the nineteenth century bods ...
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ΘTheta
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(Original post by Plato's Trousers)
This is kind of annoying, right? (and is a fact that seems to have slipped by me un-noticed throughout my A levels and degree!)

So if it's not the polarity that gives the anode and cathode their name, what is it?
According to my textbook, the anode is where the anions (from the salt bridge) moves to, and the cathode is where the cations (again from the salt bridge) moves to, in an electrochemical cell.
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charco
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(Original post by ΘTheta)
According to my textbook, the anode is where the anions (from the salt bridge) moves to, and the cathode is where the cations (again from the salt bridge) moves to, in an electrochemical cell.
You are missing the point.

The cathode is negative in an electrolytic cell and positive in an electrochemical cell.
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Plato's Trousers
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(Original post by ΘTheta)
According to my textbook, the anode is where the anions (from the salt bridge) moves to, and the cathode is where the cations (again from the salt bridge) moves to, in an electrochemical cell.

(Original post by charco)
You are missing the point.

The cathode is negative in an electrolytic cell and positive in an electrochemical cell.
Indeed.

My question was essentially how come sometimes the anode is positive and other times it's negative? i.e. what does anode/cathode actually mean if it doesn't refer to the electrical polarity?
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charco
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(Original post by Plato's Trousers)
Indeed.

My question was essentially how come sometimes the anode is positive and other times it's negative? i.e. what does anode/cathode actually mean if it doesn't refer to the electrical polarity?
I can only suggest wiki:

"A cathode is an electrode through which electric current flows out of a polarized electrical device. The direction of electric current is, by convention, opposite to the direction of electron flow—thus, electrons are considered to flow toward the cathode electrode while current flows away from it. This convention is sometimes remembered using the mnemonic CCD for cathode current departs."
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Plato's Trousers
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(Original post by charco)
I can only suggest wiki:

"A cathode is an electrode through which electric current flows out of a polarized electrical device. The direction of electric current is, by convention, opposite to the direction of electron flow—thus, electrons are considered to flow toward the cathode electrode while current flows away from it. This convention is sometimes remembered using the mnemonic CCD for cathode current departs."
Hmm... so I guess the question is really what we mean by "out of"

CATHODE
In a device that provides power (a battery) current flows from the electrolyte to the outside world (so it's the positive terminal), but in a device that consumes power (an electrolytic cell) current flows from the outside world to the electrolyte (so it's the negative terminal).
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mphysical
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(Original post by ΘTheta)
But here is what I don't understand though, if the electrons are made by the oxidation at the anode, which flow through the wires, is that not reducing the voltage as there is a current (flow of electrons) flowing through the voltmeter? :confused::confused::confused::confused:
Thanks
Electrons are not 'made by the oxidation at the anode' they are already present in the circuit wire.
The voltage 'pushes' the electrons around the circuit.
The electrons flowing though the voltmeter are minimal due to the high resistor.
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ΘTheta
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(Original post by mphysical)
Electrons are not 'made by the oxidation at the anode' they are already present in the circuit wire.
The voltage 'pushes' the electrons around the circuit.
The electrons flowing though the voltmeter are minimal due to the high resistor.
So how would the electrons get from the anode to the cathode to reduce species? :confused::confused::confused:
Thanks!
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