Oxidation and reduction. 2 Flashcards by Sara li

Define oxidation in terms of electron transfer

Oxidation is the loss of electrons

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define reduction in terms of electron transfer

Reduction is the gaining of electrons

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if a substance loses electrons, it is …..

oxidised

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if a substance gains electrons, it is …

reduced

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what are redox reactions

one substance is oxidised and one substance is reduced simutaneously (one cannot occour without the other)

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what is an oxidising agent/ reagent

a substance that causes oxidation in another substance
(It itself is reduced)

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what is a reducting agent

substance that causes reduction in another substance
(itself is oxidised)

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Give an example of an oxidising agent used in swimming pools

Chlorine is added to swimming pools to disinfect them

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Explain how oxidising agent s and reducting agents are used in different bleaches

Oxidising agent Sodium hypocloride in household bleaches
Reducing agentsulfur dioxide is used to bleach wood

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Define oxidation number

the charge an atom has or appears to have when electrons are distributed according to certain rules

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In any neutral compound/molecule the sum of the oxidation numbers must equal…

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In any complex ion, the sum of all the oxidation numbers must equal…

The charge of the ion

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A free element (Diatomic element) (An element not bonded to another element or bonded to itself) always has an oxidation number of….

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The oxidation number of an simple ion is equal to…

the charge of the ion

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Oxygen 99% of the time has a oxidation number of…

-2 in its compounds

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Hydrogen 99% of the time has an oxidation number of…

+1 in its compounds

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Fluorine always has an oxidation number of..

-1 in its compounds

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Group 1 elements always have an oxidation number of …and
Group 2 elements always have an oxidation number of…

+1
+2

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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

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When is hydrogen oxidation not +1

In a metal hydride where it has an oxidation number of -1
hydrodengen is more electronegative than the metal

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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 ## Footnote To study halogens as oxidising agents 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 ## Footnote 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 ## Footnote 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 ## Footnote 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 ## Footnote 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 ## Footnote 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 ## Footnote 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-)**

writw two balanced equations to describe this expeirment | 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 copper vs Zinc

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 copper vs mg

Mg - 2e- --> Mg2+ Cu 2+ +2e- --> Cu↓

Describe any difference in what was observed between adding the zinc to a copper (II) solution and adding the magnesium to a copper (II) solution, and explain why this is the case in terms of relative reducing abilities of: a) Zinc metal and copper metal b) Magnesium metal and copper metal

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