A redox reaction is a type of chemical reaction that involves two opposite, yet complementary processes - reduction and oxidation (redox). By being complementary, it means that one cannot occur without the other; while one is giving out, the other is receiving. We know that the act of giving can never be complete if there is nothing no one to receive. Therefore, while oxidation is the loss of electrons or increase in oxidation number, reduction is said to be gain of electrons or decrease (reduction) in oxidation number.
Example:
Zn(s) + Cu2+(aq) ---> Zn(aq) + Cu(s)
In the above equation, the zinc metal displaces the copper(II)ion out of solution to form zinc ion and Cu metal. The oxidation state/number of zinc changes from 0 to +2 (increase) due to the loss of 2 electrons, while the oxidation state/number of copper changes from +2 to 0 (decrease) because it gained the 2 electrons that were lost by the zinc metal.
We can also define oxidation as the addition of oxygen or removal of hydrogen to a substance, while reduction is the removal of oxygen or addition of hydrogen to a substance.
Examples:
a) C + O2 ---> CO2 (oxidation)
b) CuO + H2 ---> Cu + H2O (reduction)
From the above examples, carbon undergoes oxidation to carbon(IV)oxide in (a) because oxygen was added to it. In (b), the copper(II)oxide is reduced to copper metal by the hydrogen gas, which removed the oxygen from it to form water.
Oxidation is also said to be the addition of an electronegative elements to a substance, while reduction is removal of an electronegative element from a substance.
Examples:
c) 2FeCl2 + Cl2 ---> 2FeCl3
d) Zn + 2HCl ---> ZnCl2 + H2
In (c) above, the iron(II)chloride is oxidized to iron(III)chloride because an atom of Cl is added to it by the chlorine gas (which incidentally is reduced to chloride); while in (d), the hydrochloric acid is reduced to hydrogen gas because the Cl atom is removed by the zinc metal, which in turn is oxidized to zinc chloride.
Oxidizing & Reducing Agents
As stated earlier, redox reactions involve the acts of 'giving' and 'receiving'. This implies that in every reaction of this nature, there must be two parties - the giver and the receiver. Now, let's call the receiver - the oxidizing agent and the giver - the reducing agent. I know someone would be wondering: what is given out and received?, and the answer is electrons. Now, having understood this concept, let's attempt to define oxidizing and reducing agents.
Reducing agent is the specie that loses (gives out) electron(s) in a redox reaction and gets oxidized in the process, while the oxidizing agent is the specie that accepts (receives) electron(s) and gets reduced in the process.
How can they be identified in a reaction? Simple!, - using the changes in their oxidation states. The specie whose change in oxidation state is positive (an increase) is the reducing agent, while the one whose change in oxidation state is negative (a decrease) is the oxidizing agent.
Let's use the simple reaction between sodium and chlorine to form sodium chloride as an illustration.
2Na + Cl2 ---> 2(Na+)(Cl-)
R.A. O.A
From the above, the sodium metal is the reducing agent (RA), while the chlorine gas is the oxidizing agent (OA).
The Na atom loses 1 electron to become positively charged, Na+. Its oxidation state changes from 0 to +1 as shown below:
Na ---> (Na+) + e- …………(i)
Change in oxidation state = +1 - 0 = +1
Since the change in the oxidation state of Na in the reaction is +ve (an increase from 0 to 1), it means it is oxidized.
The Cl molecule gains the electron lost by Na atom to become negatively charged, Cl-. Its oxidation state changes from 0 to -1 as shown below:
Cl2 + 2e- ---> 2Cl-…………(ii)
Change in oxidation state = -1 - 0 = -1
Since the change in the oxidation state of Cl in the reaction is -ve (a decrease from 0 to -1), it means it is reduced.
Also, an oxidizing agent can be described as an oxygen donor or a hydrogen remover, while a reducing agent is a hydrogen donor or oxygen remover, as explained in the example below:
CuO(s) + H2(g) ---> Cu(s) + H2O(g)
O.A. R.A.
The above reaction is known as the reduction of black copper(II)oxide to brown copper metal using hydrogen gas. In the equation, CuO is the oxidizing agent because it oxidizes the hydrogen gas to water molecule by donating the O atom attached to it; whereas, H2 is the reducing agent because it reduces the copper(II)oxide to copper metal by removing the O atom attached to it (CuO). In the process, the oxidizing agent is reduced while the reducing agent is oxidized.
Examples of important oxidizing agents include : potassium tetraoxomanganate (VII) (KMnO4), potassium heptaoxodichromate (VI) (K2Cr2O7), the halogens (such as fluorine (F2), chlorine (Cl2), bromine (Br), iodine (I2)), oxygen gas (O2), sulphur(IV)oxide (SO2) etc
Examples of important reducing agents are: lithium tetrahydridoaluminate (III) (LiAlH4), sodium tetrahydridoborate (III) (NaBH4), alkali and alkaline-earth metals such as sodium, lithium, potassium, calcium, hydrogen sulphide (H2S), sulphur(IV)oxide etc
Do These:
1. Zn + CuSO4 ---> ZnSO4 + Cu
In the reaction above, the reducing agent is: A. Zn B. CuSO4 C. ZnSO4 D. Cu
2. H2O + C ---> H2 + CO
The oxidizing agent in the reaction above is: A. CO B. H2 C. H2O D. C
3. Which of the following acts as both a reducing and an oxidizing agent? A. H2 B. SO2 C. H2S D. CO2
4. ZnO + CO heat Zn + CO2
---->
In the reaction above, zinc has been: A. decomposed B. displaced C. oxidized D. reduced
5. If Y is an oxidizing agent that reacts with a reducing agent, Z, which of the following is correct? A. Y increases in oxidation number B. Y becomes reduced C. Z loses protons D. Z gains protons
6. Which specie undergoes reduction in the reaction represented by the equation below?
H2S + FeCl3 ---> S + 2HCl + 2FeCl2
A. Fe3+ B. H2S C. Cl- D. S
Follow us on Twitter: @gmtacademy
WhatsApp: 07034776117
Example:
Zn(s) + Cu2+(aq) ---> Zn(aq) + Cu(s)
In the above equation, the zinc metal displaces the copper(II)ion out of solution to form zinc ion and Cu metal. The oxidation state/number of zinc changes from 0 to +2 (increase) due to the loss of 2 electrons, while the oxidation state/number of copper changes from +2 to 0 (decrease) because it gained the 2 electrons that were lost by the zinc metal.
We can also define oxidation as the addition of oxygen or removal of hydrogen to a substance, while reduction is the removal of oxygen or addition of hydrogen to a substance.
Examples:
a) C + O2 ---> CO2 (oxidation)
b) CuO + H2 ---> Cu + H2O (reduction)
From the above examples, carbon undergoes oxidation to carbon(IV)oxide in (a) because oxygen was added to it. In (b), the copper(II)oxide is reduced to copper metal by the hydrogen gas, which removed the oxygen from it to form water.
Oxidation is also said to be the addition of an electronegative elements to a substance, while reduction is removal of an electronegative element from a substance.
Examples:
c) 2FeCl2 + Cl2 ---> 2FeCl3
d) Zn + 2HCl ---> ZnCl2 + H2
In (c) above, the iron(II)chloride is oxidized to iron(III)chloride because an atom of Cl is added to it by the chlorine gas (which incidentally is reduced to chloride); while in (d), the hydrochloric acid is reduced to hydrogen gas because the Cl atom is removed by the zinc metal, which in turn is oxidized to zinc chloride.
Oxidizing & Reducing Agents
As stated earlier, redox reactions involve the acts of 'giving' and 'receiving'. This implies that in every reaction of this nature, there must be two parties - the giver and the receiver. Now, let's call the receiver - the oxidizing agent and the giver - the reducing agent. I know someone would be wondering: what is given out and received?, and the answer is electrons. Now, having understood this concept, let's attempt to define oxidizing and reducing agents.
Reducing agent is the specie that loses (gives out) electron(s) in a redox reaction and gets oxidized in the process, while the oxidizing agent is the specie that accepts (receives) electron(s) and gets reduced in the process.
How can they be identified in a reaction? Simple!, - using the changes in their oxidation states. The specie whose change in oxidation state is positive (an increase) is the reducing agent, while the one whose change in oxidation state is negative (a decrease) is the oxidizing agent.
Let's use the simple reaction between sodium and chlorine to form sodium chloride as an illustration.
2Na + Cl2 ---> 2(Na+)(Cl-)
R.A. O.A
From the above, the sodium metal is the reducing agent (RA), while the chlorine gas is the oxidizing agent (OA).
The Na atom loses 1 electron to become positively charged, Na+. Its oxidation state changes from 0 to +1 as shown below:
Na ---> (Na+) + e- …………(i)
Change in oxidation state = +1 - 0 = +1
Since the change in the oxidation state of Na in the reaction is +ve (an increase from 0 to 1), it means it is oxidized.
The Cl molecule gains the electron lost by Na atom to become negatively charged, Cl-. Its oxidation state changes from 0 to -1 as shown below:
Cl2 + 2e- ---> 2Cl-…………(ii)
Change in oxidation state = -1 - 0 = -1
Since the change in the oxidation state of Cl in the reaction is -ve (a decrease from 0 to -1), it means it is reduced.
Also, an oxidizing agent can be described as an oxygen donor or a hydrogen remover, while a reducing agent is a hydrogen donor or oxygen remover, as explained in the example below:
CuO(s) + H2(g) ---> Cu(s) + H2O(g)
O.A. R.A.
The above reaction is known as the reduction of black copper(II)oxide to brown copper metal using hydrogen gas. In the equation, CuO is the oxidizing agent because it oxidizes the hydrogen gas to water molecule by donating the O atom attached to it; whereas, H2 is the reducing agent because it reduces the copper(II)oxide to copper metal by removing the O atom attached to it (CuO). In the process, the oxidizing agent is reduced while the reducing agent is oxidized.
Examples of important oxidizing agents include : potassium tetraoxomanganate (VII) (KMnO4), potassium heptaoxodichromate (VI) (K2Cr2O7), the halogens (such as fluorine (F2), chlorine (Cl2), bromine (Br), iodine (I2)), oxygen gas (O2), sulphur(IV)oxide (SO2) etc
Examples of important reducing agents are: lithium tetrahydridoaluminate (III) (LiAlH4), sodium tetrahydridoborate (III) (NaBH4), alkali and alkaline-earth metals such as sodium, lithium, potassium, calcium, hydrogen sulphide (H2S), sulphur(IV)oxide etc
Do These:
1. Zn + CuSO4 ---> ZnSO4 + Cu
In the reaction above, the reducing agent is: A. Zn B. CuSO4 C. ZnSO4 D. Cu
2. H2O + C ---> H2 + CO
The oxidizing agent in the reaction above is: A. CO B. H2 C. H2O D. C
3. Which of the following acts as both a reducing and an oxidizing agent? A. H2 B. SO2 C. H2S D. CO2
4. ZnO + CO heat Zn + CO2
---->
In the reaction above, zinc has been: A. decomposed B. displaced C. oxidized D. reduced
5. If Y is an oxidizing agent that reacts with a reducing agent, Z, which of the following is correct? A. Y increases in oxidation number B. Y becomes reduced C. Z loses protons D. Z gains protons
6. Which specie undergoes reduction in the reaction represented by the equation below?
H2S + FeCl3 ---> S + 2HCl + 2FeCl2
A. Fe3+ B. H2S C. Cl- D. S
Follow us on Twitter: @gmtacademy
WhatsApp: 07034776117
RA-C02 membagi 2 Agen Judi Online
ReplyDelete