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chemistry > REDOX, ELECTROLYSIS, VOLTAIC > Flashcards

REDOX, ELECTROLYSIS, VOLTAIC Flashcards

1
Q

oxidation=

A
  • gain of oxygen
  • increase in oxidation number
  • loss of hydrogen
  • loss of electron
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2
Q

on of atoms in uncombined state=

A

0

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3
Q

on of gp 1 and gp 2 elements in their compounds=

A

+1, +2

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4
Q

on of oxygen in all its compounds=

A

-2

  • except in perioxide = -1
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5
Q

on of gp 7/17 in all their compounds=

A

-1

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6
Q

on of hydrogen in all its compounds=

A

+1

  • except in metal hydride = -1

w/ metal = -1

w/ non metal = -1

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7
Q

on of monoatomic ion=

A

charge present on the ion

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8
Q

sum of on in a compound=

A

0

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9
Q

sum of on in polyatomic ion=

A

charge present on ion

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10
Q

if substance is oxidised it is

A

reductant/reducing agent

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10
Q

if substance is reduced it is

A

oxidant/oxidising agent

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11
Q

metal+water

A

metal hydroxide+hydrogen

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12
Q

when group 1 metal react what happens

A

metal floats, fizzes
- as you go down the group reactivity increases so more vigours reaction with pottasium than with lithium for example

enough heat given out to ignite the h2 gas which ignites the potassium itself

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13
Q

when group 2 metal react with water

A
  • react less vigoursly than group 1
  • metal sinks to the bottom, small bublles of h2 gas appear on surface
  • hydroxides formed by group 2 are partially water soluble
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14
Q

transition metals reaction w/ water

A

generally do not react

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15
Q

reaction of metal w/ air

A

metals react with oxygen in the air to form metal oxides

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16
Q

reactivity series of metals

A

katrina [K]
ne [Na]
car [Ca]
mangi [Mg]
alto [Al]
[C]
zen [Zn]
ferrari [Fe]
phirbhi [Pb]
haye [H]
kyo [Cu]
mili [mercury (Hg)]
silver [Ag]
audi [Au]
plated [Pt]

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17
Q

least reactive =

A

easy to discharge

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18
Q

4OH- →

A

O2+2H2O+4e-

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19
Q

anode

A

attracts anions, (+vely charged)
- oxidation @ anode (ANOX)

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20
Q

cathode

A

attracts cations, (-vely charged)
- reduction @ cathode (REDCAT)

21
Q

diatomic molecues

A

have [H2]
no [N2]
fear [F2]
of [O2]
ice [I2]
cold [Cl2]
beer [Br]

22
Q

types of electrode

A
  • intert
  • active
23
Q

inert electrode

A

does not interfere in electrolysis reaction
- ex. graphite/platinum

24
active electrodes
interfere in electrolysis reaction - ex. metal electrodes
25
battery
combination of cells
26
what happens in electrolysis?
electricity passes through compound and it dissociates the compound into corresponding elements
27
what is used to demonstrate electrolysis of water
hofmann voltameter
28
why cant do PbBr2 in electrolysis in lab
bromine gas given out is toxic
29
corrosion=?
general term that refers to the process by which metals are slowly broken down by reacting with substances in their environment - ex. rusting - iron+oxygen+water→hydrated iron (iii) oxide ## Footnote hydrated iron (iii) oxide=rust
30
conditions for rusting to take place
water, oxygen has to be present - test tube w/ only water/only air/both air and water - the one with both air and water will rust
31
what corrodes in a metal
generally only surface of metal corrodes because only surface is exposed to env
32
corrosion in fe
- in case of iron the rust formed at the surface flakes off - new metal revealed - that rusts - process continues till entire chunk of metal breaks down if left long enough
33
corrosion in Al
when top layer of al oxidises, al2o3 forms which acts as a protective layer around the Al so it is protected from rest of the environment
34
protect iron from rusing
1. barrier methods * painting * oiling/greasing * electroplating 2. sacrificial methods *add more reactive metal to the iron so that the more reactive metal corrodes instead of iron
35
ex. that uses both barrier and sacrificial methods of protection against rusting
galvanizing * object coated in layer of zinc * (electroplating + more reactive metal aded so even if zn scratched and fe exposed, zinc will reactive bc its more reactive)
36
electroplating
covering surface of one metal with another
37
what is electrolyte
substance that conducts electricity through the movement of ions | (ionic compound in molten state or aq state)
38
# electroplating anode
should be made from same material as the electroplating metal
39
# electroplating cathode
obj you want to electroplate
40
# electroplating electrolyte
must contain ions of electroplating metal
41
reaction at anode in electroplating
metal loses electrons to form ions and dissolves in the electrolyte - ex. Cu→Cu2+2e- | electrons travel through wire to the cathode where ions gain electrons
42
reaction at cathode in electroplating
ions in the electrolyte gain the electrons that come through the wire from the anode and become an atom and deposit on the cathode - ex. Cu2+ + 2e- → Cu
43
till when electroplating takes place
till anode completely finished
44
factors affectnig thicnkess of cathode in electroplating
* amount of voltage supplied * area of electrode exposed to the electrolyte (immerse deeper for more area to be exposed) * surface area of electrode exposed to electrolyte (higher means more area for the reactions to occur) * distance b/w the electrodes * conc. of electrolyte * time for which reaction happens
45
factors affecting votlage ouput by voltaic cell
* concentration of electrolyte * metals used (bc if higher up in reactivity series, electrons lost more easily so more ions able to take part in electrochemical reaction) * surface area of ectrode exposed
46
types of electrochemical cells
1. electrolytic 2. voltaic
47
electrolytic cell
electrical to chemical energy
48
voltaic cell
chemical to electrical energy
49
use of salt bridge
ions on both sides impede electron flow - so salt bridge adeded so that ions flow in the aq sol when needed to neutralise the region ## Footnote salt bridge = KNO3
50
till when voltacic cell functions?
* until anode completely depleted or * until ions in salt bridge have been completely exhausted
51
how voltaic cell works?
- more reactive metal loses electrons and becomes anode - as it loses electrons, the metal becomes ion which dissolves in the aq sol - electrons travel through wire to cathode where ions from aq sol gain e- to become atom and deposit on cathode - as this does on charges build up impeding electron flow - salt bridge added to solve the problem by constatnyl neutralising region

chemistry (10 decks)

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