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Reaction Types in Grade 11 discussed oxidation , reduction and redox reactions . Oxidation involves a loss of electrons and reduction involves a gain of electrons . A redox reaction is a reaction where both oxidation and reduction take place. What is common to all of these processes is that they involve a transfer of electrons and a change in the oxidation state of the elements that are involved.

Oxidation and reduction

  1. Define the terms oxidation and reduction .
  2. In each of the following reactions say whether the iron in the reactants is oxidised or reduced.
    1. F e F e 2 + + 2 e -
    2. F e 3 + + e - F e 2 +
    3. F e 2 O 3 + 3 C O 2 F e + 3 C O 2
    4. F e 2 + F e 3 + + e -
    5. F e 2 O 3 + 2 A l A l 2 O 3 + 2 F e
  3. In each of the following equations, say which elements in the reactants are oxidised and which are reduced.
    1. C u O ( s ) + H 2 ( g ) C u ( s ) + H 2 O ( g )
    2. 2 N O ( g ) + 2 C O ( g ) N 2 ( g ) + 2 C O 2 ( g )
    3. M g ( s ) + F e S O 4 ( a q ) M g S O 4 ( a q ) + F e ( s )
    4. Z n ( s ) + 2 A g N O 3 ( a q ) 2 A g + Z n ( N O 3 ) 2 ( a q )
  4. Which one of the substances listed below acts as the oxidising agent in the following reaction? 3 S O 2 + C r 2 O 7 2 - + 2 H + 3 S O 4 2 - + 2 C r 3 + + H 2 O
    1. H +
    2. Cr 3 +
    3. SO 2
    4. Cr 2 O 7 2 -

In Grade 11, an experiment was carried out to see what happened when zinc granules are added to a solution of copper(II) sulphate. In the experiment, the Cu 2 + ions from the copper(II) sulphate solution were reduced to copper metal, which was then deposited in a layer on the zinc granules. The zinc atoms were oxidised to form Zn 2 + ions in the solution. The half reactions are as follows:

C u 2 + ( a q ) + 2 e - C u ( s ) (reduction half reaction)

Z n ( s ) Z n 2 + ( a q ) + 2 e - (oxidation half reaction)

The overall redox reaction is:

C u 2 + ( a q ) + Z n C u ( s ) + Z n 2 + ( a q )

There was an increase in the temperature of the reaction when you carried out this experiment. Is it possible that this heat energy could be converted into electrical energy? In other words, can we use a chemical reaction where there is an exchange of electrons, to produce electricity? And if this is possible, what would happen if an electrical current was supplied to cause some type of chemical reaction to take place?

An electrochemical reaction is a chemical reaction that produces a voltage , and therefore a flow of electrical current. An electrochemical reaction can also be the reverse of this process, in other words if an electrical current causes a chemical reaction to take place.

Electrochemical reaction

If a chemical reaction is caused by an external voltage, or if a voltage is caused by a chemical reaction, it is an electrochemical reaction.

Electrochemistry is the branch of chemistry that studies these electrochemical reactions. In this chapter, we will be looking more closely at different types of electrochemical reactions, and how these can be used in different ways.

The galvanic cell

Experiment : electrochemical reactions


To investigate the reactions that take place in a zinc-copper cell


zinc plate, copper plate, measuring balance, zinc sulphate (ZnSO 4 ) solution (1 mol.dm - 3 ), copper sulphate (CuSO 4 ) solution (1 mol.dm - 3 ), two 250 ml beakers, U-tube, Na 2 SO 4 solution, cotton wool, ammeter, connecting wire.


  1. Measure the mass of the copper and zinc plates and record your findings.
  2. Pour about 200 ml of the zinc sulphate solution into a beaker and put the zinc plate into it.
  3. Pour about 200 ml of the copper sulphate solution into the second beaker and place the copper plate into it.
  4. Fill the U-tube with the Na 2 SO 4 solution and seal the ends of the tubes with the cotton wool. This will stop the solution from flowing out when the U-tube is turned upside down.
  5. Connect the zinc and copper plates to the ammeter and observe whether the ammeter records a reading.
  6. Place the U-tube so that one end is in the copper sulphate solution and the other end is in the zinc sulphate solution. Is there a reading on the ammeter? In which direction is the current flowing?
  7. Take the ammeter away and connect the copper and zinc plates to each other directly using copper wire. Leave to stand for about one day.
  8. After a day, remove the two plates and rinse them first with distilled water, then with alcohol and finally with ether. Dry the plates using a hair dryer.
  9. Weigh the zinc and copper plates and record their mass. Has the mass of the plates changed from the original measurements?

Questions & Answers

hi please help me how to balance redox reactions?
Brian Reply
Which equation do u wanna balance
i tried to write it but my phone just can't write it Cr2 O72-(aq) + H2S (aq) Cr3 (aq) + S(s)
show is the equation
hello. what is the difference between a primary, secondary and tertiary alcohol
Thokozani Reply
primary the C=bonded to 1 Carbon atom.... secondary=bonded to 2 carbon atoms tertiary=bonded to 3 carbon atoms
I hope you're answered
thanks Christina
My pleasure
Thank you Christina. This is very helpful 😀👍👍💯
Anytime Thokozani
How to calculate pH?
thank you guys i didn't know about the primary, secondary and tertiary alcohols
thank you Christina
Hey guys which topic does AC nd DC generator falls
can somebody help me with functional isomers
Baningi Reply
function isomer has the same molecular formula but different functional group
what's momentum
Luvelo Reply
the product of an objects mass times velocity. it is mainly prevalent in collisions.
Methane contains C and H. This compound is
Juan Reply
ketones's functional group
Moloi Reply
Why does the carboxyl group have acidc properties?
Evi Reply
carboxylic acids
Besides improving appearance what is another reason why medal is electro plated
Elizabeth Reply
it is made of metal
what is different between Dependent variable and independent variables
difference between A.c and D.c
AC has slip rings DC has split rings commutator
to avoid rust and to improve strength and conductivity
the variable whose value doesn't depend on other is known as independent variable ex time
are UV rays dangerous?
Khathutshelo Reply
what's this?
if there is extensive exposure, it can lead to skin cancer
yes depend upon their intensity
i hv a problem with this chapter because i also have problem with Newton's laws of motion
Kearabetswe Reply
I have a problem with calculation in Newton's law of motion
me also VuyokAzi
what's the question
Which area in particular?
just get the hang if free body diagrams,know the directions.
I know how to draw free diagram I have a problem with calculation in second law
what is the wave model of atom ?
Trazy Reply
guys what is momentum
@Luvelo... Momentum is the product of an object's mass and its velocity.
the model based on wave nature of electron
Can you state the Doppler effect in words
Nombuyiselo Reply
State Coulomb's law in words
the magnitude of the electrostatic force exerted point on each other is directly proportional to the product on magnitude of charges and inversely proportional to the square distance between them
the change in frequency of the sound detected by a listener because sound source and listener have different velocity
Newton's first law of motion
Nnuso Reply
When an object is at rest or traveling at a constant velocity it will remain at rest unless an unbalanced force acts upon it.
yes that's true
Always know Newton's second law of motion. It appears to be in every question paper
Is the normal force always 0
Mpilo Reply
no. newtons 3rd law states that if something exerts a force into something else it will experience that same magnitude of force but in the opposite direction. so the net force is equal to the force the object applies to the surface but in the opposite direction
define the term rate of reaction in word
David Reply
I think it a chemical process in which substance act mutually on each other.
how many bones are in the human body?
it's the rate at which the reactants are able to change to products
206 bones

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Source:  OpenStax, Siyavula textbooks: grade 12 physical science. OpenStax CNX. Aug 03, 2011 Download for free at http://cnx.org/content/col11244/1.2
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