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G9 + 10 chemistry > unit 7 + 8 - redox + electrolysis > Flashcards

unit 7 + 8 - redox + electrolysis Flashcards

1
Q

Redox Reaction

A

A reaction where oxidation and reduction both happen simultaneously

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2
Q

Conditions for oxidation to happen

A

1) gain of oxygen
2) Loss of electrons
3) Loss of hydrogen atoms
4) Increase in oxidation number

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3
Q

conditions for reduction to happen

A

1) loss of oxygen
2) gain of electrons
3) gain of hydrogen atoms
4) decrease in oxidation number

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4
Q

Who will undergo oxidation or reduction

A

Only reactants

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5
Q

Reactant which oxidises

A

Reductant/Reducing agent

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6
Q

Reactant which is reduces

A

Oxidizing Agent/Oxidant

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7
Q

4 main properties to remember to convert molecular equations into ionic equations

A

Solids, liquid and gases cant disassociate into ions

only aqueous solutions will disassociate

Solids always lose electrons

Aqueous will always gain electrons

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8
Q

atoms in free state oxidation no

A

0

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9
Q

oxidation number of group 1 elements in all its compounds

A

1

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10
Q

oxidation number of group 2 elements in all its compounds

A

2

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11
Q

oxidation number of oxygen in all its compounds

A

-2

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12
Q

oxidation number of group 7/17 elements in all its compounds

A

-1

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13
Q

oxidation number of hydrogen in all its compounds

A

1

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14
Q

Oxidation number of monoatomic ions

A

change present on the ions

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15
Q

Sum of oxdiation numbers in a compounds is equal to

A

0

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16
Q

Sum of oxidation number in a polyatomic ion is equal to

A

charge present on ion

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17
Q

what happens in rusting and corrosion in terms of redox reactions

A

metal is oxidized (loses electrons), and typically oxygen is reduced (gains electrons)

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18
Q

All nitrates and sulphates are ___ in water

A

soluble in water

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19
Q

colour of copper salt

A

blue, shade depends on centration of salt of copper present

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20
Q

Reactivity series of metal actual

A

K - Potassium
Na - Sodium
Ca - Calcium
Mg - Magnesium
Al - Aluminium
Zn - Zinc
Fe - Iron
Sn - Tin
Pb - Lead
[H] - hydrogen
Cu - Copper
Hg - Mercury
Ag - Silver
Au - Gold
Pt - Platinium

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21
Q

What is electrolysis

A

On passing electric current in a molten or aqueous solution a chemical reaction takes place in an ionic compound an it disassociates into its elements.

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22
Q

Electrodes

A

Electrical conductors (metals) which allow for the flow of charge to pass

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23
Q

Active Electrodes

A

Interfere with electrolysis reaction. They are mainly metals with low reactivity

24
Q

Inert electrodes

A

Dont interfere in electrolysis reaction. Mainly graphite of platinum

25
Electrolytic cell
Any appartus used in electrolysis
26
Electrolyte
Ionic compound in liquid/molten/aqueous state
27
Cathode
Negatively charged electrode (always connected to negative terminal of battery) Attracts cations in compound Reduction takes place at cathode due to gain of electrons
28
Anode
Positively charged cathode (always connected to positive terminal of battery) Attract anions in compound Oxidation takes place due to loss of electrons
29
Electrolysis of molten NaCl with Inert Graphite electrode
The cathode will attract the Na+ ions The anode wil attract the Cl- ions The battery will pull the electron from the Chlorine Ion and deliver to the cathode, where the Sodium ions bond with the electrons to form Sodium Ions, which will be present as a layer on top of the cathode. The chlorine atoms ecape as a fas
30
Electrolysis of aqueous Cu(NO3)2 with Inert Graphite electrode
The cathode will attract H+ and Cu2+ ions The anode will attract OH- and NO3- ions Since Cu2+ and OH- are less reactive (lower in their respective reactivity series) than the other molecule, they will disassociate The battery will pull the electron from the Hydroxide Ion, oxidising it, to give out H2O and O2 (the O2 gas will release as gas). The electrons will go to the cathode where Cu2+ ions reduced with them to form copper ions which will be deposited as a layer of copper on the cathode.
31
What all changes can be seen when an inert electrode is used
Colour of electrolyte fades as ions are leaving the solution No change in mass of Anode Cathode mass increase as a layer of solid is being deposited on the cathode.
32
When current flows in electrolyte vs when current flows in electrode +wires who carry the charge
Electrolyte =Ions Electrode + Wires = electrons
33
Does cathode attract more reactive or less reactive metals
Less reactive
34
Anode formula for electrolysis with aqeuous solution and inert electrode for OH^-1
4OH^-1 = O_2 + 2H_2O + 4e^-1
35
Which ions and elements move to cathode
Hydrogen and Metal Ions
36
Describe electrolysis of of aqeous solution with active electrode of Copper Sulphate
Cathode attracts H+ and Cu2+ Ions Anode attracts OH- and SO4 2- ions Similar to other,s Cu2+ will disassociate at the cathode. However since a metal is easier to dissolve, on the anode, the battery will pull electrons from the electrode. Copper will lose electrons to form copper ions which will flow back into the solution filling the hole left by the reduction of copper at cathode. The electrons from the anode will be used to bond with cu2+ to form a layer of copper on the cathpde.
37
Relation between cathode half eq and anode half eq in electrolysis of aqueous solution with actovve electrode
Just revrese the Cathode half eq to get the anode hald eq or vice versa
38
What all changes can be seen when an active electrode is used
colour of electrolyte remains the same as ions keep flowing back in the solution Anode mass decreases Cathode mass increase
39
Factors affecting deposition in Electrolysis using Active electrode
Time Voltage/Potential Difference Concentration
40
How does increasing the concentration of aqueous solutin affect the rate of deposition in active electrolysis
Increasing the concentration means more ions are present in the electrolyte and hence a greater number of ions will be attracted to the cathode forming a greater deposition layer
41
How does increasing the potential difference affect the rate of deposition in active electrolysis
Higher voltage leads to more movement of ions in the electrolyte, resulting in a greater number of metal being deposited on the cathode. According to Ohm’s Law, a greater voltage supplied means a greater current flowing through the electrolyte. Increased current enhances the rate at which metal ions are reduced and deposited on the cathode, with more ions moving towards the cathode per unit time
42
How does increasing the time affect the rate of deposition in active electrolysis
Increasing the time means a longer duration for the ions to deposit onto the cathode, hence a greater rate of deposition
43
What interference will the active electrodes have on electrolysis
At Anode, the deposition of anions will happen, however, the electrons present in element of anode will also be pulled by the battery and hence the the newly formed ions from the anode will deposit into the electrolyte, refilling the hole leaved by the cation present in the electrolyte being attached to the cathode
44
Electroplating material of anode and electrolyte
Must be the material or contain the material you wish to electroplate on cathode. Metal in electrolyte must be same as Anode
45
What is electroplating
Electrolysis of aqueous solution with anode being an active electrode to coat an object with a metal.
46
relationship between cathode half equation and anode half equation in active electrode electrolysis
The opposite of the cathode equation is the anode half equation
47
The object you want to electroplate must be the
Cathode
48
Voltaic cell, how does it work with example of daniel cell
Consider the a zinc electrode with zinc sulphate (anode) and a copper electrode in copper sulphate(cathode) The zinc atoms in the anode look to loose two electrons and copper ions in the copper sukphate want to gain them. Hence the zinc atoms become zinc ions and flow into the sinc sukphate solution. The copper ions bodn with the electrons to form copper ions and deposit onto the copper electrode However, +ve charges get accumulated on the zinc electrolytic cell and -ve charges in the copper electrolytic cell. Hence we use a salt bdirge to maintain the flow of electrons
49
Till when does a voltaic cell work
Until the anode mass is completely gone or the ions in the salt bridge are finished
50
Salt Bridge
Helps maintain neutrality of solution and helps in movement of ions (cations move to cathode and anion move to anode) Use metal of high reactivity to ensure no interference in reaction
51
Chnages in Mass of anode and cathode in voltaic cell
mass of anode decreases and mass of cathode increases
52
Factors affecting Voltage in Voltaic Cell
Electrode Material - Different materials have different tendencies to lose or gain electrons Electrolyte concentration - Increasing the electrolyte concentration in a voltaic cell increases the voltage by enhancing the availability of ions for the reaction Surface Area of electrode - A larger surface area allows for more contact between the electrode and electrolyte hence a greater voltage Temperature - Higher temperature means a higher resistance making it harder for current to flow
53
Reaction of metal with a oxide gives a? with example
Metal Oxide 2Mg + 02 -> 2MgO
54
Reaction of metal with water gives out? with example
Metal + Water -> Metal Hydroxide + Hydrogen Gas Only reactive metals can react with water, those twoards the end of the reactivity series cant react eg: 2Na + H2O -> 2NaOH + H2
55
Displacement reaction of metals with eg
A more reactive metal displaces a less reactive metal in its compound. Eg: Mg + FeSO4 -> MgSO4 + Fe However, if the lone metal is less reactive than th emetal in compound, no reaction will take place. Eg: Cu + FeSO4 -> no reaction
56
Rusting of metals
Only happens with Iron and its alloys Formula: Fe + O2 + H20 -> Fe(OH)3 + Fe2O3 + H2O
57
Methods of extraction of metals
Electrolysis Smelting Reducing by carbon

G9 + 10 chemistry (8 decks)

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