# Homework Help: Chemical equation; reaction; balancing problem.

1. Sep 21, 2009

### General_Sax

1. The problem statement, all variables and given/known data

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.

3. 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-?
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Sep 21, 2009

### 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]

3. Sep 22, 2009

### Staff: Mentor

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

4. Sep 23, 2009

### General_Sax

Thanks guys.

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