Amounts of Substances in a Chemical Reaction

You see from the preceding discussion that a balanced chemical equation relates the amounts of snbstances in a reaction. The coefficients in the equation can be given a molar interpretation, and using this interpretation you can, for example, calculate the moles of product obtained from any given moles of reactant. Also, yon can extend this type of calcnlation to answer questions about masses of reactants and products. 

Again consido- the Haber process for producing ammonia gas. Suppose you have a mixture of H2 and N2, and 4.8 mol H2 in this mixture reacts with N2 to produce NH3. How many moles of NH3 can you produce from this quantity of H2 In asking questions like this, yon assume Ihat the mixture contains a sufficient quantity of the other reactant (N2, in this case). 

The balanced chemical equation for the Haber process tells you that 3 mol H2 produce 2 mol NH3. You can express this as a conversion factor  

Multiplying any qnantity of H2 by this conversion factor mathematically converts that quantity of H2 to the quantity of NH3 as specified by the balanced chemical eqnation. Note that yon write the conversion factor with the quantity you are converting from on the bottom (3 mol H2), and the quantity you are converting to on the top (2 mol 

To calculate the quantity of NH3 produced from 4.8 mol H2, you write 4.8 mol H2 and multiply this by the preceding conversion factor  

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Reaction stoichiometry compares the amounts of substances in a chemical reaction. 

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