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When constructing chemical equations, how can you work out the subscript of each product. For example:

$$\ce{3Ca + N2-> Ca3N2}$$

How do I know that it's $\ce{Ca}$ with a little 3 and N with a little 2.

airhuff
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Millie
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    Welcome to Chemistry.SE. Those subscripts come from the minimum number of calcium and nitride ions needed to product a charge-balanced neutral ionic compound. Here is a related question on nomenclature of binary compounds that covers some of the basics: https://chemistry.stackexchange.com/questions/98159/how-to-name-binary-inorganic-compounds-given-their-chemical-formula-and-vice – Ben Norris Nov 25 '19 at 18:05
  • For more information on the linear algebra check out the book "Chemical Reaction Equilibrium Analysis: Theory and Algorithms" by Missen & Smith. – B. Kelly Nov 25 '19 at 20:13

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When constructing chemical equations, you cannot work out the subscript of each product. The formula cannot be guessed. In your example, you must know the formula $\ce{Ca, N2}$ and $\ce{Ca3N2}$. This being given, your job is to find the good coefficients 3, 1 and 1.

airhuff
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Maurice
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    I hope nobody thinks that people study chemistry to make their living after graduation in a job where they balance equations all day as their prime task. – Karsten Nov 25 '19 at 22:30