Chemsitry: Redox Equations Flashcards

1
Q

When is a redox equation balanced?

A

-numbers of atoms of each element on both sides are the same
-total charge same on both sides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What steps do you take in order to balance an unbalanced redox equation?

A

-write oxidation states above each element
-identify species oxidised and reduced
-determine amount of electrons gained/lost
-balance number of electrons gained/lost
-balance remaining atoms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Using the unbalanced equation, MnO4- + Fe2+ + H+ -> Mn2+ + Fe3+ + H2O, show the steps involved to balance this redox equation?

A
  1. oxidation states above each species
    Mn: +7 O4: -2 Fe: +2 H: +1 -> Mn: +2 Fe: +3 H: +1 O: -2
  2. identify species oxidised and reduced
    Mn: +7 -> Mn:+2 reduction, gain 5e-
    Fe: +2 -> +3 oxidation, loss 1e-
  3. balance number of electrons transferred
    MnO4- + 5e- -> Mn2+
    Fe2+ -> Fe3+ + e-
    therefore multiple by 5
    MnO4- + 5Fe2+ + H+ -> Mn2+ + 5Fe3+ + H2O
  4. balance all other elements involved
    MnO4- + 5Fe2+ + 8H+ -> Mn2+ + 5Fe3+ + 4H2O
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What happen in a disproportionation reaction?

A

atoms of same element both reduced and oxidised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

If an element has been oxidised, on what side are the electrons added in a half equation?

A

side of products

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

If an element has been reduced, what side are the electrons added to?

A

side with reactants

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do you find the number of electrons transferred from oxidation states?

A

the difference between oxidation states

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

If the oxidation state increases, has it been oxidised or reduced?

A

oxidised

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

If the oxidation state decreases, has the element been oxidised or reduced?

A

reduced

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Using the example, 3Cu + 8H+ + 2NO3 -> 3Cu2+ + 2NO + H2O, show how you would find the half equations

A

Cu: 0 H+: +1 N: +5 O: -2 -> Cu: 2+ N: +2 O: -2 H:+1 O: -2
3Cu -> 3Cu2+ Cu: increase by +2 3Cu: 2x3 = 6 6 electrons transferred
3Cu -> 3Cu2+ + 6e-
2NO3- -> 2NO N: increase by +3 2N: 3x2=6 6 electrons transferred
2NO3- + 6e- -> 2NO
however oxygen molecules not accounted for, add H+ to reactants and H2O to products
2NO3- + 8H+ + 6e- -> 2NO + 4H2O

How well did you know this?
1
Not at all
2
3
4
5
Perfectly