Unit 3/4 Chemistry-Y12 REDOX Flashcards
REDOX-12THAUG TEST
Oxidation can be identified by?
Gain in oxidation number
Loss of electrons
Gain of oxygen
Loss of hydrogen
Reduction can be identified by ?
Loss in oxidation number
Gain of electrons
Loss of Oxygen
Gain of hydrogen
In oxidation where are the electron in the redox half equation?
RHS.
In reduction where are the electrons in the redox half equation?
LHS.
Important Oxidation rules?
- Fluorine is always -1
- When hydrogen is bonded to non-metal it is +1, but when it bonded to metals it is -1.
- Oxygen is -2 in compounds, but in peroxides, it is -1 e.g. Na2o2.
- Group 7 elements are -1 but if 2 group 7 elements are present in a compound then the more electronegative one is the one that carries the -1.
A electrochemical series compares and help us do?
It compares the relevant strength of oxidants and reductants and it helps us determine whether a reaction will occur spontaneously or not.
What would be the impact of a failure of a salt bridge/ if it was removed/stopped working in a galvanic cell?
Without the salt bridge/ if it stops working/fails to work , the electron flow will not happen inside the galvanic cell, so it will not be able to generate electricity or the electric current.
Oxidation always occurs at the?
Anode.
Reduction always occurs at the?
Cathode.
What is a galvanic cell?
A galvanic cell is a chemical system that produces an electric current (DC) from a spontaneous redox reaction.
How to calculate cell potential?
E(cathode) - E(anode).
what are the state symbols for the reactants that are molten ionic compounds in electrolytic cells?
Liquid.
what are the state symbols for the products that are molten ionic compounds in electrolytic cells?
Liquid or gas.
Why is an external power supply used in an electrolytic cell?
An external power supply is used to supply electrical energy to force a non-spontaneous chemical reaction to occur.
What are the electrodes called in an electrolytic cell and what are the charges?
Anode which is +.
Cathode which is -.
What are the electrodes called in a galvanic cell and what are the charges?
Anode which is -.
Cathode which is +.
Electron flow is always?
From the anode to the cathode.
Why is a mesh divider used in an electrolysis cell?
A mesh divider is used as some of the reactants might spontaneously react otherwise.
Which type of cell uses a chemical reaction to produce electricity?
Galvanic cell.
What part of a galvanic cell contains and inert electrolyte, and is necessary to complete the circuit and prevent build up of charge?
Salt bridge.
EXAM Q: Draw and label the apparatus you could use in the laboratory for the electrolysis of molten potassium chloride?
electrolytic cell draw it and use book to mark it pg.49
EXAM Q: List some industrial applications of electrolysis?
Electroplating, electrorefining and electrolysis of water.
EXAM Q: State the method for the extraction of aluminum? NOT NEEDED
- Treat bauxite with Naoh to remove impurities.
- Dissolve the al2o3 in molten cryolite, the cryolite has a lower melting point
than alumina ( 10009 deg compared to 2072 deg), which reduces operating
costs. - Electrolyze using graGphite electrodes.
Oxidation half equation: 202-(l)->o2(g)+ 4e-
Side reaction: Co(l)+o2(g)–> Co2(g)
Describe the KOHES PROCESS not exam question but need to know to balance equations….
- Balance no. of electrons of the element that changes in oxidation no.
- Balance oxygen atoms by adding water.
- Balance hydrogen atoms by adding H+ ions.
- Balance charges on both sides by adding electrons to the more positive side.
- Add state symbols.
Galvanic Vs Direct Contact
- Direct contact: oxidant and reductant react with one another and there is an electron transfer between them that cannot be detected. Energy is realised in the form of heat.
- Galvanic cell: The electrons move from the reductant to the oxidant and are forced to travel along the external wiring to reach the oxidant. This can be detected by a voltmeter. This flow of electrons creates a direct electric current and thus the chemical energy of the reactants is transformed into heat energy.
Draw a Danielle cell with (Zn and Cu) the zn and cu will remain the same if exam question is draw a Danielle cell
Daniell cell:
- draw a little wave of water IF THIS IS NOT THERE U WILL GET 0MARKS
- Anode is zinc. Anode half eq: zn(s)- zn2+ (aq) + 2e. Anode solution is zinc nitrate solution.
- Cathode is copper. Cathode half eq: cu2+(aq)+2e– cu(s). Cathode solution is copper(II) nitrate solution.
- Salt bridge (K+) goes into the cathode and (NO3-) goes into the anode.
- Indicate that anode is zn(s) and cathode is cu(s) and point an arrow to the respective electrodes to show this.
- Eelectron flow from anode to cathode
- Label that Oxidation is at the anode and reduction is at the cathode.
Galvanic cell cathode+ or -?
- (+).
Galvanic cell anode+ or -?
- (-).
In oxidation, electrons are on the LHS OR RHS?
RHS.
In reduction, are electrons on the LHS OR RHS?
LHS.
In an electrolytic cell is the cathode + or -?
- (-).
In an electrolytic cell is the anode + or -?
- (+).
What part of the galvanic cell contains an inert electrolyte, and is necessary to complete the circuit and prevent the build-up of charge?
- The salt bridge.
Molten VS Aqueous/ solution: NaCl list the reactants for both molten and aqueous/solution.
- NaCl (l)/molten= Na+ and Cl-
- NaCl (aq)/solution= Na+, cl- and H2o.
When electroplating which electrode will the electroplated metal be deposited?
- Cathode.
Electrorefining is and example of?
- Is an example of purifying metals using electrolysis.
In electrorefining where would the pure and impure metal be?
- Pure is at cathode and impure is at anode.