Zero order

[IreneSeo3F]

In week 9&10's sapling #7, the reactions is
2A(g)+2B(g)+C(g)⟶3G(g)+4F(g)
For this reaction, the initial conc. of C is different in all the experiments and the order of reactant C is zero.

If a reactant's initial concentration is different in all the experiments, can I automatically assume that the order of the reactant is zero?

[Andreas Krumbein 1L]

Not necessarily; what you should be looking for is an experiment where all of the other reactants' initial concentrations are held constant and only the reactant in question is allowed to change. This allows us to know that if the initial reaction rate changes, it changes as a result of the aforementioned reactant, and none of the other ones. If you look at the first experiment and the last one, you will notice that reactant C is halved while A and B are held constant. However, the initial reaction rate does not change, so we know that reactant C has no effect on the reaction rate, hence it is 0th order.

[Sharon Kim 2A]

In this question, they give you a chart! You cannot tell if the order of a reactant unless you do the calculations by dividing each initial rates and cancelling out constants to find each order.

[Francesca_Borchardt_2D]

In week 9&10's sapling #7, the reactions is
2A(g)+2B(g)+C(g)⟶3G(g)+4F(g)
For this reaction, the initial conc. of C is different in all the experiments and the order of reactant C is zero.

If a reactant's initial concentration is different in all the experiments, can I automatically assume that the order of the reactant is zero?

Hello, I would not assume that because in order to find the order of a reaction, you need to do calculations. Because there was a chart, you just have to make sure you look at the concentrations where A and B are constant and C changes.

[Rachael Cohen 3G]

I think it's always best to do the calculations to determine the order. In this question, the reason all of the C concentrations are different and it is zero order is because two of the experiments had the same rate. Because a change in the concentration of C did not affect the rate, we know it is zero order.

[Jaden Joodi 3J]

While it might have panned out this way for this question, it is possible to have two of the same concentrations of [C] that is meant to show that one of the other reactants is is affecting the initial rate.