110 Chapter Three Stoichiometry What will the container look like if the reaction between Nz(g) and Hz(g) proceeds to completion? Remember that each N z requires 3 Hz. Circling groups of reactants, we have H2 /.!2. .---,\-, / j \ /' \ I I ~ /\' I /r \\ I'l)) , \', ~j I I " <, v-'/ \ •l ','---~ ~.--N z NH3 Before the reaction After the reaction In this case, the hydrogen (H 2 ) is limiting. That is, the Hz molecules are used up before all the N, molecules are consumed. In this situation the amount of hydrogen limits the amount of product (ammonia) that can form-hydrogen is the limiting reactant. Some N z mole-cules are left over in this case because the reaction runs out of Hz molecules first. To deter-mine how much product can be formed from a given mixture of reactants, we have to look for the reactant that is limiting-the one that runs out first and thus limits the amount of product that can form. In some cases, the mixture of reactants might be stoichiometric-that is, all reactants
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