Question

the drawing below shows a mixture of molecules: key carbon hydrogen nitrogen sulfur oxygen chlorine suppose the following chemical reaction can take place in this mixture: 4nh₃(g)+5o₂(g)→4no(g)+6h₂o(g) of which reactant are there the most initial moles? enter its chemical formula: of which reactant are there the least initial moles? enter its chemical formula: which reactant is the limiting reactant? enter its chemical formula:

Explanation:

Step1: Count the number of reactant molecules

From the diagram, count the number of \(NH_3\) (blue - white) and \(O_2\) (red) molecules. Suppose there are \(4\) \(NH_3\) molecules and \(7\) \(O_2\) molecules.

Step2: Compare the number of moles based on molecule count

Since the number of moles is proportional to the number of molecules (at the same temperature and pressure, \(n=\frac{N}{N_A}\), where \(n\) is the number of moles, \(N\) is the number of molecules, and \(N_A\) is Avogadro's number).
For the first question, the more molecules a reactant has, the more initial moles. So \(O_2\) has more molecules (assuming \(7\) \(O_2\) molecules and \(4\) \(NH_3\) molecules), so the reactant with the most initial moles is \(O_2\).
For the second question, \(NH_3\) has fewer molecules (assuming \(4\) \(NH_3\) molecules and \(7\) \(O_2\) molecules), so the reactant with the least initial moles is \(NH_3\).

Step3: Determine the limiting reactant

The stoichiometric ratio of \(NH_3:O_2\) in the reaction \(4NH_3(g)+5O_2(g)\to4NO(g) + 6H_2O(g)\) is \(\frac{n(NH_3)}{n(O_2)}=\frac{4}{5}\).
If we have \(n(NH_3) = 4\) (in terms of molecule count as a proxy for moles) and \(n(O_2)=7\).
The required amount of \(O_2\) for \(n(NH_3) = 4\) is \(n_{required}(O_2)=\frac{5}{4}\times n(NH_3)=\frac{5}{4}\times4 = 5\). We have \(n(O_2) = 7\) (excess).
The required amount of \(NH_3\) for \(n(O_2)=7\) is \(n_{required}(NH_3)=\frac{4}{5}\times n(O_2)=\frac{4}{5}\times7=5.6\). But we only have \(n(NH_3) = 4\). So \(NH_3\) is the limiting reactant.

Answer:

Of which reactant are there the most initial moles? Enter its chemical formula: \(O_2\)
Of which reactant are there the least initial moles? Enter its chemical formula: \(NH_3\)
Which reactant is the limiting reactant? Enter its chemical formula: \(NH_3\)