variable oxidation states

Question 1

what is the most common oxidation state and why

Answer 1

2+

represents loss of electrons from the 4s subshell

Question 2

why is

Fe3+[Ar]3d5 more stable than Fe2+[Ar]3d6

Answer 2

electron configurations with half filled 3d subshell are more stable than others

Question 3

give the name for the ion

VO⁺₂

Answer 3

vanadyl (v)

Question 4

give the name for the ion

VO²⁺

Answer 4

vanadyl (IV)

Question 5

give the name for the ion

V3+

Answer 5

vanadium (III)

Question 6

give the name for the ion

V2+

Answer 6

vanadium (II)

Question 7

what colour is VO⁺₂

Answer 7

yellow

Question 8

what colour is VO²⁺

Answer 8

blue

Question 9

what colour is V3+

Answer 9

green

Question 10

what colour is V2+

Answer 10

purple

Question 11

what is vanadium reduced with

Answer 11

zinc and sulfuric acid (can be any acid)

Question 12

what is vanadium oxidised with

Answer 12

manganate (VII) solution

Question 13

what 3 things affect the redox potential for transition metal ion being reduced

Answer 13

• pH
• type of ligand
• conditions
  (temperature, pressure, concentration)

Question 14

give the equation for the redox titration between iron (II) and manganate (VII)

Answer 14

5Fe2+ + MnO4- + 8H+ —-> Mn2+ + 5Fe3+ + 4H2O

Question 15

what are redox titration based on

Answer 15

redox titrations are based on change in oxidation state

Question 16

what is the colour change for the redox titration between iron (II) and manganate (VII)

Answer 16

permanent pink due to MnO4- being present (self indicating)

Question 17

write an equation for the redox titration of ethanedioate and manganate (VII)

Answer 17

5C2O4 2- + 2MnO4- + 16H+ —-> 10CO2 + 8H2O + 2Mn2+

Question 18

what would you expect when you carry out a redox titration of ethanedioate and manganate (VII)

(2 marks)

Answer 18

• permanent pink due to MnO4- being present
  (self indicating)
• effervescence due to CO2