Balancing / Skeletal Equations

[Melissa Villanueva1K]

Why is it that when we are balancing skeletal equations, we usually add an H+ or H20 to the chemical equation? Thanks!

[Kyle Golden Dis 2G]

We sometimes add H2O or H+ to balance redox reactions to ensure to correct amount of oxygens and hydrogens are balanced on each side.

[KimGiang2F]

Sometimes when balancing the skeletal equation, one species may have oxygen on one side of the reaction and not the other. Essentially, you would need to add H2O to balance the O atoms and balance the H atoms by adding H+ where necessary.

[Nicole Elhosni 2I]

You also need to take whether it is in an acidic or basic solution into consideration (this will be told).
If it is occurring in an acidic solution, you will balance the O with H2O and the H with H+.
If it is occurring in a basic solution, you will balance the O with H2O and the H with H2O, and add OH- to the other side of the rxn.

[Luc Lorain 1L]

We actually get both H₂O and either H⁺?OH^- from the set up of the experiment itself. It is important to note that when balancing equations we are trying to use the existing components to accurately explain a reaction; we are never adding substances to an equation in which they would not already be present.

Typically we utilize aqueous reducing and oxidizing agents when creating a galvanic cell (though non-aqueous batteries do exist in scientific literature); therefore, water will be present as a solvent as a "hidden" element in the equation. We then use the oxygen found in water to balance for oxygen in the reaction if there are disparities in skeletal redox equation (ex. SO₄--> SO₃).

Like the poster above me stated, the pH of the solution will impact whether we balance with H⁺ or OH^-. As we learned in the equilibrium unit, there will always be a certain concentration of either species in water, as H₂O expresses autoprotolysis. The pH of a solution reflects the concentration of H⁺ ions in concentration-- when low, there are many more H⁺ ions available to interact with other species in solution, and when high, OH^- is instead abundant for the same purposes. We use these species to balance the number of hydrogen atoms on either side of a half-reaction, as the earlier act of balancing with H₂O adds 2H atoms per each molecule used.