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Redox Equations in Basic Solution
Half Reaction Method
Part 2The Redox Equation
Here, we’ll use the half-reactions we came up with and balanced in Part 1 to build an equation for the overall Redox Reaction taking place. We’ll balance it in acid solution here. Then in Part 3, we will convert it to Basic Solution
Here are the two balanced half-reactions we obtained in Part 1.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H 2e
HPO 5H 3e P 3H 2O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
The 2 half-reactions webalanced in Part 1
In order to add these up and obtain the overall redox equation, we must look at the electrons.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
2NH OH N 2H O 2H 3
HPO 5H
2e
3e P 3H O 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
We see that 3 electrons and gained by the lower half-reaction, and (click) 2 electrons are lost by the top half-reaction.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
2NH OH N 2H O 2H 3
HPO 5H
2e
3e P 3H O 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
So the electrons gained are NOT equal to the electrons lost. We must multiply these half-reactions by factors which will make the electrons gained equal to those lost
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
2NH OH N 2H O 2H 3
HPO 5H
2e
3e P 3H O 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
e–’s gained ≠ e–’s gained
The lowest common multiple of 3 and 2, is 6. Therefore we multiply by factors which will make electrons gained and electrons lost, both equal to 6.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
2NH OH N 2H O 2H 3
HPO 5H
2e
3e P 3H O 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Lowest common multiple of 3 and 2 is 6
So we multiply the top half-reaction by 3,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H 3e P 3H
2e
O 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
And the bottom half-reaction by 2
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H P 33 H
2e
Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
So 2 × 3 = 6 electrons are gained by the bottom half-reaction
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H P 33 H
2e
Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
6 e– gaine
d
And 3 × 2 = 6 electrons are lost by the top half-reaction.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H P 33 H
2e
Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
6 e– lost
So, because electrons gained are now equal to electrons lost,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H P 33 H
2e
Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
6 e– lost
6 e– gaine
d
The electrons can be cancelled from the half-reactions
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H P 33 H
2e
Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
So now we’re left with these.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H P 33 H
2e
Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
At this point, we add what we have on the left and right of the arrows to obtain the equation for the overall redox reaction.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H P 33 H
2e
Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Starting on the top left, we have (click) 3 × 2 NH2OH
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
22
2 2
3
32NH O N 2H O 2H
HPO 5H P 3H O
2e
3
H
e 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Which gives us 6 NH2OH
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
22
2 2
3
32NH O N 2H O 2H
HPO 5H P 3H O
2e
3
H
e 2
23 22 2 22HPO 10H 3N 6H O 66N H 2 OH OH P 6H 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
And on the bottom left, we have 2 × HPO3 (2 minus)
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
22
2
3
2 32NH OH N 2H O 2H
5H P 3H
2e
HPO e O3 2
23 22 2 22HPO 10H 3N 6H O 66N H 2 OH OH P 6H 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Which we’ll add here,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
22
2
3
2 32NH OH N 2H O 2H
5H P 3H
2e
HPO e O3 2
2 2 2 2236NH OH 10H 3N 6H O 6H2HP 2P 6HO O 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
And 2 × 5 H+,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO P 3H O
2e
H 3 2e5
2 2 2 2236NH OH 10H 3N 6H O 6H2HP 2P 6HO O 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Which equals 10 H+.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO P 3H O
2e
H 3 2e5
22 3 2 2 26NH OH 2HPO 3N 6H O 6H 2P1 6H O0H
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Now for the right side. On the top right we have (click) 3 × 1 N2,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
22 2
23 2
32NH OH 2H O 2H
HPO 5H P 3
2
H
eN
3 Oe 2
2 3 2 222 3N6NH OH 2HPO 10H 6H O 6H 2P 6H O 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Which is 3 N2,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
22 2
23 2
32NH OH 2H O 2H
HPO 5H P 3
2
H
eN
3 Oe 2
2 3 2 222 3N6NH OH 2HPO 10H 6H O 6H 2P 6H O 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
3 × 2 H2O,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2
23 2
2 32NH OH N 2H
HPO 5H P 3H O
O 2e
3
2H
e 2
2 3 2 222 3N6NH OH 2HPO 10H 6H O 6H 2P 6H O 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Which is equal to 6 H2O,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2
23 2
2 32NH OH N 2H
HPO 5H P 3H O
O 2e
3
2H
e 2
22 3 2 226NH OH 2HPO 10H 3N 6H6H O 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
And 3 times 2 H+,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O
HPO 5H P 3
2H
H O
2e
3e 2
22 3 2 2 26NH OH 2HPO 10H 3 6HN 6H O 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Which equals 6 H+.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O
HPO 5H P 3
2H
H O
2e
3e 2
22 3 2 2 26NH OH 2HPO 10H 3 6HN 6H O 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
On the bottom right, we have 2 × P
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H 3P H
2e
3 Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2 HP 6 O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Which is equal to 2 P
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2 2 2
23 2
32NH OH N 2H O 2H
HPO 5H 3P H
2e
3 Oe 2
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2 HP 6 O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
And 2 × 3 H2O,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22
2 3 2 26NH OH 2HPO 10H 3N 6H O 6H 2 HP 6 O 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Which is equal to 6 H2O.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22
2 3 2 26NH OH 2HPO 10H 3N 6H O 6H 2 HP 6 O 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Now we have the balanced redox equation.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Balanced Redox Equation
But it has H+ ions on both sides,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
And two sets of water molecules on the right side,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
So this equation must be simplified
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Must Be Simplified
We start by removing 6 H+ ions from both sides,
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 3N 6H O 2P 6H O10H 6H
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Remove 6 H+ ions from Both Sides
Removing 6 H+ ions from the right side, leaves us with none
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 3N 6H O 2P 6H O10H 6H
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Remove 6 H+ ions from Both Sides
And Removing 6 H+ ions from the left side leaves us with 10 – 6 (click), or 4 H+ ion
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 3N 6H O 2P 6H O10H 6H
22 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Remove 6 H+ ions from Both Sides
4
We simplify the water by adding the two sets of 6 H2O molecules on the right side
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
2 22
2 3 26NH OH 2HPO 10H 3N 6H6H O O2P 6H 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
Add up the two sets of H2O molecules
4
To give us 12 water molecules altogether.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
2 22
2 3 26NH OH 2HPO 10H 3N 6H6H O O2P 6H 2
2 3 2 2
2
22 3 2 2
6NH OH 2HPO 4H 3N 12H O 2P
4H O 4H 4OH
6NH OH 2HPO 3N 8H O 2P 4OH
6H2O + 6H2O = 12H2O
+124
We’ll re-write this equation in more compact form here
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2
2
22
2
3 2 2
4H O 4H 4OH
6NH OH
6NH OH 2HPO 4H 3N 12H O
2HPO 3N 8H O
2P
2P 4OH
+124
So now we have the redox equation balanced in acid solution. At this point, pause the video and check to see that all atoms are balanced and total ionic charge is balanced
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2
2
22
2
3 2 2
4H O 4H 4OH
6NH OH
6NH OH 2HPO 4H 3N 12H O
2HPO 3N 8H O
2P
2P 4OH
+124
Balanced Redox Equation in Acid Solution
However, the original question wants us to balance this equation in BASIC solution
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2
2
22
2
3 2 2
4H O 4H 4OH
6NH OH
6NH OH 2HPO 4H 3N 12H O
2HPO 3N 8H O
2P
2P 4OH
+124
Balanced Redox Equation in Acid Solution
So this equation needs to be converted to Basic Solution
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2
2
22
2
3 2 2
4H O 4H 4OH
6NH OH
6NH OH 2HPO 4H 3N 12H O
2HPO 3N 8H O
2P
2P 4OH
+124
Convert to Basic Solution
In the next video, which is Part 3, we will convert this redox equation to basic solution.
Write a balanced redox equation in basic solution, given the skeleton equation:
22 3 2NH OH HPO N P
2
2
2 2
23
32NH O
3
2e
3
H N 2H O 2H
HPO 5H P H 2e O
22 3 2 2 26NH OH 2HPO 10H 3N 6H O 6H 2P 6H O
22 3 2
2
22
2
3 2 2
4H O 4H 4OH
6NH OH
6NH OH 2HPO 4H 3N 12H O
2HPO 3N 8H O
2P
2P 4OH
+124
In PART 3 (the next video) we’ll Convert this to Basic
Solution
