What is the rate of the reaction 4 nh3 + 5 o2 → 4 no + 6 h2o when 0.0500 mol/l of nh3 is being consumed per second? 1. 0.0125 m·sec−1 2. one of the other answers has the right number but the units are wrong. 3. −0.0125 m·sec−1 4. 0.200 m·sec−1 5. −0.200 m·sec−1?

The only information in this problem that we are given with are the stoichiometric coefficients in the reaction, and the rate of disappearance of NH₃ as 0.05 M/s. The rate of disappearance always has a negative sign. The general formula would be:

Rate of Reaction = -(ΔNH₃/Δtime)(1/v), where v is the stoichiometric coefficient of NH₃ in the reaction

Substituting the values,
Rate of Reaction = -(0.05 M/s)(1/4) = -0.0125 M/s