Answer:
Sign = Negative, since ammonia is a reactant.
Value = 1 / 4 (Inverse of it's coefficient in the equation)
Explanation:
4NH3(g) + 5O2(g) --> 4NO(g) + 6H2O(g)
The Reaction Rate for a given chemical reaction is the measure of the change in concentration of the reactants or the change in concentration of the products per unit time.
For a reaction of the form A+B→C
the rate can be expressed in terms of the change in concentration of any of its components;
rate = −Δ[A] / Δt
rate = − Δ[B] / Δt
rate = Δ[C] / Δt
Considering a reaction in which the coefficients are different:
A + 2B → 2D
It is clear that [B] decreases two times as rapidly as [A], so in order to avoid ambiguity when expressing the rate in terms of different components, it is customary to divide each change in concentration by the appropriate coefficient:
rate = − Δ[A] / Δt = − Δ[B] / 2Δt= Δ[D] / 2Δt
Things to Note;
- For products, the sign is always positive and for reactants, the sign is always negative.
- The Numerical value is usually the inverse of the coefficient.
Rate Expression of change in [ammonia] over time for the rate expression of ammonia:
Sign = Negative, since ammonia is a reactant.
Value = 1 / 4 (Inverse of it's coefficient in the equation)
