Question

Which one of the following is not a valid expression for the rate of the reaction below?

4NH₃ + 7O₂ → 4NO₂ + 6H₂O

A) - 1/7 Δ[O₂]/Δt
B) - 1/4 Δ[NH₃]/Δt
C) 1/4 Δ[NO₂]/Δt
D) 1/6 Δ[H₂O]/Δt
E) All of the above are valid expressions of the reaction rate

Answer 1

The valid expression for the rate of the reaction is - 1/4 Δ[NH₃]/Δt.

Step-by-step explanation:

The balanced chemical equation shows that 2 mol of N₂O5 must decompose for each 1 mol of O₂ produced and that 4 mol of NO₂ are produced for every 1 mol of O₂ produced. The molar ratios of O₂ to N₂O5 and to NO₂ are thus 1:2 and 1:4, respectively. This means that the rate of change of [N₂O5] and [NO₂] must be divided by its stoichiometric coefficient to obtain equivalent expressions for the reaction rate. For example, because NO₂ is produced at four times the rate of O2, the rate of production of NO₂ is divided by 4. The valid expression for the rate of the reaction is:

B) - 1/4 Δ[NH₃]/Δt