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Published byClarence Marquis Modified about 1 year ago

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Here, we’ll go through an example of balancing a redox equation in acid solution using the half-reaction method.

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We’re asked to write a balanced redox equation, given the skeleton equation: H 3 PO 3 + U gives P + UO 2+ Write a balanced redox equation, given the skeleton equation:

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We will work through this problem using two separate videos: Part 1 – Balancing the Half-reactions ( Acid Solution ) Part 2 – Building the Redox Equation ( Acid Solution ) Part 3 – Converting to Basic Solution Write a balanced redox equation, given the skeleton equation:

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In this video, Part 1, we’ll split the skeleton equation into two half-reactions, and balance them in acid solution We will work through this problem using two separate videos: Part 1 – Balancing the Half-reactions ( Acid Solution ) Part 2 – Building the Redox Equation ( Acid Solution ) Part 3 – Converting to Basic Solution Write a balanced redox equation, given the skeleton equation:

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And in the next video, Part 2, we’ll use these half-reactions to build the overall Redox equation. We will work through this problem using two separate videos: Part 1 – Balancing the Half-reactions ( Acid Solution ) Part 2 – Building the Redox Equation ( Acid Solution ) Part 3 – Converting to Basic Solution Write a balanced redox equation, given the skeleton equation:

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We start by splitting the equation into two half-reactions. The first one will be (click) H3PO3 producing P. We’ll balance this half-reaction now. Write a balanced redox equation, given the skeleton equation:

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We’ll start by balancing phosphorus atoms, we see there is one P on both sides, so it is already balanced. Write a balanced redox equation, given the skeleton equation: 11

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Now we’ll move on to oxygen. There are 3 O’s on the left and none on the right, Write a balanced redox equation, given the skeleton equation: 3

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So we’ll add 3 water molecules to the right side. Write a balanced redox equation, given the skeleton equation: 3

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We now have 3 O’s on both sides, so oxygen is balanced. Write a balanced redox equation, given the skeleton equation: 3 3

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Now we’ll balance hydrogen (click) we have 3 H’s on the left and 6 H’s on the right. Write a balanced redox equation, given the skeleton equation: 36

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So we need to add 3 more H’s to the left side. Write a balanced redox equation, given the skeleton equation: 36 Need to add 3 H’s to the left side

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We accomplish this by adding 3 H+ ions to the left side Write a balanced redox equation, given the skeleton equation: 36 Add 3 H + to the left side

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Now we have 6 H’s on both sides of the equation, so hydrogen is balanced. Write a balanced redox equation, given the skeleton equation: 363

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The next step is to balance charge. On the left, we have a total ionic charge of Write a balanced redox equation, given the skeleton equation: +30

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Which add up to +3 Write a balanced redox equation, given the skeleton equation: +30

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And on the right side, both P and 3 H2O have a charge of zero Write a balanced redox equation, given the skeleton equation:

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So the total charge on the right side is zero Write a balanced redox equation, given the skeleton equation: +30

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To balance charge, we add 3 electrons to the more positive side, the left side. Write a balanced redox equation, given the skeleton equation: +30 Add 3 e – to the more positive side

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This half reaction is now balanced. Write a balanced redox equation, given the skeleton equation: Balanced

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Now, we’ll start the half-reaction in which U produces UO2 plus Write a balanced redox equation, given the skeleton equation:

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The element other than hydrogen or oxygen is uranium, or U. There is one U atom on both sides, so uranium is already balanced. Write a balanced redox equation, given the skeleton equation: 11

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Next, we’ll balance oxygen. We have one O atom on the right side, but none on the left. Write a balanced redox equation, given the skeleton equation: 1

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So we add one water molecule to the left side Write a balanced redox equation, given the skeleton equation: 1

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Now we have one O atom on both sides, so oxygen is balanced. Write a balanced redox equation, given the skeleton equation: 11

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At this point, we’ll balance hydrogen atoms, Write a balanced redox equation, given the skeleton equation:

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We have 2 H atoms on the left and none on the right. Write a balanced redox equation, given the skeleton equation: 2

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To balance H’s, we add 2 H + ions to the right Write a balanced redox equation, given the skeleton equation: 2

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Now we have 2 H atoms on both sides, so hydrogen is balanced. Write a balanced redox equation, given the skeleton equation: 22

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In the next step we balance ionic charge. Looking on the left side, we see both U and H2O have zero charges Write a balanced redox equation, given the skeleton equation: 00

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So the total charge on the left side is zero Write a balanced redox equation, given the skeleton equation: 00 0

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Looking on the right side the UO2+ ion and the 2H+ ions both have a total charge of +2. Write a balanced redox equation, given the skeleton equation:

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So the total charge on the right is positive 2 and positive 2, which add up to +4. Write a balanced redox equation, given the skeleton equation:

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To balance charge, we add 4 electrons to the right side.. Write a balanced redox equation, given the skeleton equation: Add 4 e –

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The total charge on the right side is now positive 2 plus positive 2 plus negative 4, Write a balanced redox equation, given the skeleton equation: –4

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Which adds up to zero, the same as the total charge on the left side, Write a balanced redox equation, given the skeleton equation: –4

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So this half reaction is now balanced. Write a balanced redox equation, given the skeleton equation: Balanced

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Here are the equations for the two half-reactions that are taking place here. Write a balanced redox equation, given the skeleton equation:

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The top half-reaction is reduction, because electrons are gained Write a balanced redox equation, given the skeleton equation: reduction

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And the lower half-reaction is oxidation, because electrons are being lost. Write a balanced redox equation, given the skeleton equation: reduction oxidation

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The 2 half-reactions are now balanced in acid solution. In the next video, Part 2, we’ll use these to build the equation for the Overall Redox Reaction Write a balanced redox equation, given the skeleton equation: The 2 half-reactions are now balanced in acid solution. In Part 2, we’ll use these to build the equation for the Overall Redox Reaction oxidation reduction

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