Balancing Redox Reactions in Basic Solutions

[RoKe]

Formation of Hydrazine from Ammonia and Chloramine in basic solution.
NH3 + NH2Cl -> N2H4 + Cl-
What are the coefficients of NH3, OH-, and N2H4 in the balanced equation?
I basically just balanced the hydrogens with an H+, then those with OH-, and got:
NH3 + NH2Cl + OH- ->N2H4 + Cl- + H2O
This is the right answer according to my answer sheet (1, 1 and 1), I was just wondering if this is the correct method. I'm not sure how I would use a half-reaction method here and at my university it's recommended we do not use the oxidation number method. Any explanations on how to approach these problems would be appreciated.

 

[Gokul43201]

What you've done works just fine. When the question states that the reaction is happening under basic (or alkaline) conditions, you want the equation to involve OH- rather than H+, as you finally have.

The reason what you did worked is because H was the only unbalanced species in the given equation; all other elements were balanced.

Different equations are best solved using different tools (by simply matching numbers of atoms, or using the oxidation number method, or using the half reaction method). In this case, I would have done it the same way you did.

 

[Blueshift5]

Your approach to balancing the equation using H+ and OH- ions is correct. In this case, the reaction is taking place in a basic solution, so it is appropriate to use OH- ions to balance the hydrogens. The half-reaction method is typically used for balancing redox reactions, where there is a transfer of electrons between species. In this case, it seems like there is no change in oxidation states for any of the elements, so the half-reaction method may not be necessary. However, if you do want to use the half-reaction method, you can split the overall reaction into two half-reactions: the oxidation of NH3 to N2H4 and the reduction of NH2Cl to Cl-. Then, balance each half-reaction individually using the appropriate coefficients and combine them to get the overall balanced equation.