redox

Question 1

what is redox chemistry about?

Answer 1

electron transfer and the ability for electrons to be transferred

Question 2

define oxidation

Answer 2

loss of electrons

Question 3

define reduction

Answer 3

gain of electrons

Question 4

define static electricity

Answer 4

electrons from either substance have been displaced

Question 5

what are redox reactions?

Answer 5

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

Question 6

the species that undergoes oxidation is…

Answer 6

the reductant

Question 7

the species that undergoes reduction is…

Answer 7

the oxidant

Question 8

trends in electronegativity. what substance is most electronegative?

Answer 8

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

Question 9

defin electronegativity

Answer 9

ability to attract electrons

Question 10

define strong oxidant

Answer 10

really wants to under go reduction

Question 11

define strong reductant

Answer 11

really wants to undergo oxidation

Question 12

the transfer of electrons is?

Answer 12

simultaneous and spontaneous

Question 13

what determines if a redox reaction will occur?

Answer 13

downhill gradient

Question 14

what does a half cell do?

Answer 14

host a redox half reaction

Question 15

what happens when two half cells are joined?

Answer 15

a full redox reaction can occur

Question 16

describe a solid-aqueous half cell

Answer 16

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

Question 17

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

Answer 17

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

Question 18

describe the aqueous-gaseous half cell

Answer 18

• inert electrode

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

Question 19

what is the energy transformation of galvanic cells?

Answer 19

chemical to electrical energy (electricity- flow of electrons)

Question 20

what was the Daniel cell experiment observations?

Answer 20

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)

Question 21

what is a conductor?

Answer 21

allows passage if e-. metals are conductors

Question 22

define dissociation

Answer 22

when ionic compounds break apart eg. form aqueous solution

Question 23

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

Answer 23

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

Question 24

what occurs at the cathode? what is the polarity?

Answer 24

reduction. +

Question 25

what occurs at the anode? polarity?

Answer 25

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

Question 26

what happens to concentration if the ion at the anode?

Answer 26

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

Question 27

what happens to concentration of the ion at the cathode?

Answer 27

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

Question 28

define voltage

Answer 28

the push in electrons

Question 29

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

Answer 29

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

Question 30

how does gradient link to voltage

Answer 30

greater gradient, greater voltage

Question 31

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

Answer 31

- chemicals used in industry - transport of chemicals - extraction of metals eg. mining

Question 32

oxidation numbers do what in oxidation?

Answer 32

increase

Question 33

oxidation numbers do what in reduction?

Answer 33

decrease

Question 34

what is the oxidation number rule for free elements?

Answer 34

- solids, liquids, gases - ox no of 0 - H2O and other free compounds have an ox no of 0 too

Question 35

what is the oxidation number rule for ions

Answer 35

- the same as charge

Question 36

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

Answer 36

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

Question 37

balancing complex redox reactions rules

Answer 37

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