Chemical equation; reaction; balancing problem.

[General_Sax]

Homework Statement

All of a sample of Mg(OH)₂ was converted to Mg₃N₂ by:

Mg₃N₂ -> Mg(OH)₂

Give the mole ration of Mg(OH)₂ to Mg₃N₂ in that reaction.

The Attempt at a Solution

Well I'm having trouble just making heads or tails of the equation in the first place. Should I sart balancing by adding the missing elements/ions, ie, the N₂, and OH^-?

 

[drizzle]

1] 3Mg(OH)2+2NH3=Mg3N2+6H2O


2] 3Mg(OH)2+N2O=Mg3N2+3H2O+2O2

the first is more appropriate [not sure if it's possible to have oxygen gas as a product of a chemical reaction]

 

[Borek]

You don't have to balance any reaction - number of moles of Mg doesn't change, so it will be always 3 moles of Mg(OH)₂ giving one mole of Mg₃N₂.

Such approach is quite effective and fast when you do stoichiometric questions - there is no need to waste time on balancing other elements, when you can predict molar ratio of reagent and substrate just from formulas and mass conservation.

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methods

 

[General_Sax]

Thanks guys.