Chemistry - Oxidation and Reduction 2 Flashcards Part 2
Oxidation is the loss of electrons from an atom or ion. It increases the oxidation state and often occurs with reduction in redox reactions. Reduction is the gain of electrons by an atom or ion. It decreases the oxidation state and always happens alongside oxidation.
Define oxidation in terms of electron transfer
Oxidation is the loss of electrons
Key Terms
Define oxidation in terms of electron transfer
Oxidation is the loss of electrons
define reduction in terms of electron transfer
Reduction is the gaining of electrons
if a substance loses electrons, it is …..
oxidised
if a substance gains electrons, it is …
reduced
what are redox reactions
one substance is oxidised and one substance is reduced simutaneously (one cannot occour without the other)
what is an oxidising agent/ reagent
a substance that causes oxidation in another substance
(It itself is reduced)
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| Term | Definition |
|---|---|
Define oxidation in terms of electron transfer | Oxidation is the loss of electrons |
define reduction in terms of electron transfer | Reduction is the gaining of electrons |
if a substance loses electrons, it is ….. | oxidised |
if a substance gains electrons, it is … | reduced |
what are redox reactions | one substance is oxidised and one substance is reduced simutaneously (one cannot occour without the other) |
what is an oxidising agent/ reagent | a substance that causes oxidation in another substance |
what is a reducting agent | substance that causes reduction in another substance |
Give an example of an oxidising agent used in swimming pools | Chlorine is added to swimming pools to disinfect them |
Explain how oxidising agent s and reducting agents are used in different bleaches | Oxidising agent Sodium hypocloride in household bleaches |
Define oxidation number | the charge an atom has or appears to have when electrons are distributed according to certain rules |
In any neutral compound/molecule the sum of the oxidation numbers must equal… | 0 |
In any complex ion, the sum of all the oxidation numbers must equal… | The charge of the ion |
A free element (Diatomic element) (An element not bonded to another element or bonded to itself) always has an oxidation number of…. | 0 |
The oxidation number of an simple ion is equal to… | the charge of the ion |
Oxygen 99% of the time has a oxidation number of… | -2 in its compounds |
Hydrogen 99% of the time has an oxidation number of… | +1 in its compounds |
Fluorine always has an oxidation number of.. | -1 in its compounds |
Group 1 elements always have an oxidation number of …and | +1 |
When is Oxygens number not -2, And explain why | In peroxides ( Bonded w/ H) where its -1 as oxygen is more electronegative (H2O2) In Oxygen difluoride OF2 (+2) F is more electronegative element |
When is hydrogen oxidation not +1 | In a metal hydride where it has an oxidation number of -1 |
Define oxidation in terms of change in oxidation number | Oxidation is a increase in oxidation number |
define reduction in terms of a change in oxidation number | reduction is a decrease in oxidation number |
How does the oxidation number of the oxidising agent change during a redox reaction | decreases |
how does the oxidation number of the reducting agent change during a redox reaction | increases |
what is the electrochemical series | series of metals arranged in order of how esliry they lose electrons |
what does a metal higher in the electrochemical series do to one lower in the series | will reduce a metal lower down and displace it from a compound |
Name the metals in decending order from most to least reactive | postassim Sodium Calcium Magnesium Alminium Zinc Iron Lead Hydrogen Copper Silver Gold |
Writea balanced equation for the reaction that occours when magnesium is placed in copper II sulfate solution. Explain this reaction and describe what is observed | Magnesium is higher than copper in the electrochemical series. Mg reduces copper and desplaces copper from the compound Blue colour of copper II sulfate becomes colourless Brown precipate of copper metal forms |
What is observed when copper is placed in dilute sulfuriic acid, explain | copper is lower than hydrogen in the electrochemical series and will not reduce and displace it from a compound |
Give an application of knowledge of the electrochemical series | iron is used to reduce and dispace less reactive metal such as copper copper is useful in electronic industury (wires) |
Which metals from the electrochemical series are found free in nature? and why? | Lead, sopper, silver, Gold. These metals are at the bottom of the electrochemical sries and are very unreactive |
Describe the procedure and name the result/observation chlorine to oxidise bromine ions Br- to Br2 | add some chlorine water to a potassium bromide solution The solution turns red due to the formation of bromine Br2 |
write two half equations describing the reaction To study halogens as oxidising agents chlorine to oxidise bromine ions Br- to Br2 | Oxidation 2Br- - 2e- --> Br2 Reduction C2 + 2e- --> 2Cl- |
State your conclusion as a result of this expeirment To study halogens as oxidising agents chlorine to oxidise bromine ions Br- to Br2 | Chlorine has a higher ocidising ability than bromine and will oxdise bromine |
state the procedure and the obervation/ result To study halogens as oxidising agents Using chlorine to oxidise iodide ions to iodine I- to I2 | Add clorine water to postassium iodine The solution turns red-brown due to the formation of Iodine. |
state two half reactions that describe the reaction To study halogens as oxidising agents Using chlorine to oxidise iodide ions to iodine I- to I2 | Oxidation 2I- - 2E- --> 2Cl- Reduction Cl2 + 2e- ---> 2Cl |
describe the conclusion from this expeirment To study halogens as oxidising agents Using chlorine to oxidise iodide ions to iodine I- to I2 | Chlorine has a higher oxidising ability than iodine |
Why are halogens good oxidising agents | they have high electronegativity values |
Why does the reactivity/ oxidising ability of the halogens decrease going down the group | atomic radius increases going down the group, no increase in effective nuclear charge |
describe the procedure and the result/observation | Using a halogen to oxidise Fe2+ ions to Fe3+ ions | add cl water to iron sulfate solution. Add dilute sodium hydroxide solution to bring Fe3+ ions out of solution. Result: A green-brown precipate conforms the presence of Fe3+ ions |
Write two half equations of describing this reaction | Using a halogen to oxidise Fe2+ ions to Fe3+ ions | Oxidation 2Fe2+ - 2e- --> 2Fe3+ reduction Cl2 + 2e --> 2Cl- |
Describe the conclusion Using a halogen to oxidise Fe2+ ions to Fe3+ ions | clorine / bromine/ iodine is the oxdising agent |
Describe the result / observation | Use halogens to oxidise sulfite ions (SO3 2-) to sulfate ions (SO4 2-) | Add barium chloride: a white percipate forms. Add HCL If the white percipate dissolves the ions are sulfite (so3 2-) If the white percipate remains the ions are suldate (SO4 2-) |
write two balanced equations to describe this experiment | Use halogens to oxidise sulfite ions (SO3 2-) to sulfate ions (SO4 2-) | Oxidation SO3 2- + H2O --> So4 2- + 2H+ Reduction Br2 + 2e- --> 2Br - |
Describe the conclusion | Use halogens to oxidise sulfite ions (SO3 2-) to sulfate ions (SO4 2-) | the halogens are the oxidising agent |
Describe the procedure and the result/obervation | Displacement reactions of metals | Add zinc powder to copper II sulfate.A brown precipitate of copper metal forms. The blue solution of the copper suldate soltuions slowly become colourless |
Write two half equations to describe this expeirment | Copper vs Zinc displacement reaction of metals | Zn - 2e- ---> Zn2+ Cu2+ + 2e ---> Cu↓ |
describe the procedure and the result/ obervation of this reaction | copper vs mg displacement reaction | add magnesium ribbon to a copper II Sulfate soltuion Result/ Observation A brown precipation of copper metals forms. The blue colour of copper sulfate solution rapidly becomes colourless |
Write two half equations to describe this reaction | Displacement reactions of metals | Mg - 2e- --> Mg2+ Cu 2+ +2e- --> Cu↓ |
Describe any difference in what was observed between adding the zinc to a copper (II) solution | The blue colour of copper (II) sulfate decolourises more rapidly/ to a greater degree when megnesium is added than when zinc is added a) zinc is higher than copper in the electrochemical sries and has a higher reducing ability. zinc is only slightly higher than copper so reaction occours slowly. b) mg is higher than copper in electrochemica series (higher reducting bility) Mg is much higher i=than copper in electrochemical series, this occour more rapidly |