Half-Basic




Click below to see the other techniques for balancing redox equations. 



Half-Basic

Balancing Redox Equations for Reactions in Basic Conditions Using the Half-reaction Method

Redox reactions are also commonly run in basic solution, in which case, the reaction equations often include H2O(l) and OH-(aq). You may know the formulas for the reactants and products for your reaction, but you may not know whether the H2O(l) and OH-(aq) are reactants or products. For example, you may know that solid chromium(III) hydroxide, Cr(OH)3, reacts with aqueous chlorate ions, ClO3-, in basic conditions to form chromate ions, CrO42-, and chloride ions, Cl-. Because the reaction requires basic conditions, you assume that H2O(l) and OH-(aq) participate in some way, but you do not know whether they are reactants or products, and you do not know the coefficients for the reactants and products. An unbalanced equation for this reaction might be written

 

Cr(OH)3(s) + ClO3-( aq)  -->  CrO42-(aq) + Cl-(aq)   (basic)

The process for balancing a redox reaction run in basic solution is very similar to the steps for balancing redox equations for acidic solutions. We first balance the equation as if it were in acidic solution, and then we make corrections for the fact that it is really in basic solution.

Click here to see the sample study sheet for this method.

Click here to see an example.

Click here to see an exercise that will allow you to try this task yourself. 

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