Ammonia, nh3, can be made by reacting nitrogen and the equation is n2 + 3h2 --> 2nh3 how many moles of nh3 can be made if 18 moles of h2 react with enough n2?

N2 + 3 H2 -> 2 NH3 
Just use their stoichiometric coefficients (number before the chemical's name) from the balanced chemical reaction to make ratios and solve for the unknown. In this case, 2 moles of NH3 are produced for every 3 moles of H2. Thus, 
7.5 moles H2 x (2 moles NH3 / 3 moles H2) = 5 moles NH3 
Thunderclan89

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