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Chemistry > redox > Flashcards

redox Flashcards

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1
Q

what is redox chemistry about?

A

electron transfer and the ability for electrons to be transferred

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2
Q

define oxidation

A

loss of electrons

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3
Q

define reduction

A

gain of electrons

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4
Q

define static electricity

A

electrons from either substance have been displaced

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5
Q

what are redox reactions?

A

the combination of reduction and oxidation in the hopes of electron transfer

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6
Q

the species that undergoes oxidation is…

A

the reductant

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7
Q

the species that undergoes reduction is…

A

the oxidant

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8
Q

trends in electronegativity. what substance is most electronegative?

A

increases left to right and down to up. fluorine is most electronegative

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9
Q

defin electronegativity

A

ability to attract electrons

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10
Q

define strong oxidant

A

really wants to under go reduction

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11
Q

define strong reductant

A

really wants to undergo oxidation

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12
Q

the transfer of electrons is?

A

simultaneous and spontaneous

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13
Q

what determines if a redox reaction will occur?

A

downhill gradient

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14
Q

what does a half cell do?

A

host a redox half reaction

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15
Q

what happens when two half cells are joined?

A

a full redox reaction can occur

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16
Q

describe a solid-aqueous half cell

A
  • metal insert
  • electrolyte contains the same metal in ion form
    solid: electrode
    aqueous: electrolyte
17
Q

describe an aqueous-aqueous half cell. what is the electrode for?

A
  • both aqueous
  • inert electrode (solid) such as platinum or graphite is needed
    electrode conducts the electrons
18
Q

describe the aqueous-gaseous half cell

A
  • inert electrode

- as gas (product or reactant) is involved there is a tube

19
Q

what is the energy transformation of galvanic cells?

A

chemical to electrical energy (electricity- flow of electrons)

20
Q

what was the Daniel cell experiment observations?

A

Zn2+/Zn and Cu2+/Cu

  • CuSO4 (aq) electrolyte became pale in colour
  • Cu (s) electrode was covered in a film of black solid
  • Zn (s) decreased in mass
  • reaction between Cu2+ and Zn (s)
21
Q

what is a conductor?

A

allows passage if e-. metals are conductors

22
Q

define dissociation

A

when ionic compounds break apart eg. form aqueous solution

23
Q

what does a salt bridge do? what ions are used?

A

prevents flow of electrons stopping by preventing accumulation of charge and completing the circuit. ones that are always soluble- K+ and NH4+ and SNAPE

24
Q

what occurs at the cathode? what is the polarity?

A

reduction. +

25
Q

what occurs at the anode? polarity?

A

oxidation. - because this is where electrons are being shot out

26
Q

what happens to concentration if the ion at the anode?

A

due to oxidation, the ion concentration increases making a positive charge which is balanced with the salt bridge

27
Q

what happens to concentration of the ion at the cathode?

A

due to reduction, the ion concentration decreases making the electrolyte more negative. this is neutralised by the salt bride

28
Q

define voltage

A

the push in electrons

29
Q

how is electromagnetic force (emf) or E0 value calculated?

A

cathode reaction or reduction or higher - anode or oxidation or lower reaction

30
Q

how does gradient link to voltage

A

greater gradient, greater voltage

31
Q

what can the ECST be used to predict redox reactions in:

A
  • chemicals used in industry
  • transport of chemicals
  • extraction of metals eg. mining
32
Q

oxidation numbers do what in oxidation?

A

increase

33
Q

oxidation numbers do what in reduction?

A

decrease

34
Q

what is the oxidation number rule for free elements?

A
  • solids, liquids, gases
  • ox no of 0
  • H2O and other free compounds have an ox no of 0 too
35
Q

what is the oxidation number rule for ions

A
  • the same as charge
36
Q

what is the oxidation number rule for polyatomic ions? oxygen and hydrogen rules

A

calculate it using algebra for key elements (not oxygen or hydrogen)

oxygen: ox. no. is always -2 except in hydrogen peroxide (H2O2) where it is -1
hydrogen: always +1 except in metal hydrides (metal with hydrogen) such as NaH in which case it is -1. the is because hydrogen has an extra space to fill and will pick up an electron

37
Q

balancing complex redox reactions rules

A 
K- balance key elements
O- balance oxygen with H2O
H- balance hydrogen with H+ (protons)
E- balance electrons
S- add states

Chemistry (28 decks)

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