There is a sharp corner and the function is not continuous. Most likely that's because limiting reagent changes.

May I nitpick? It is continuous but not differentiable?

I'll add another point that took me by surprise: I would have expected a zero derivative at x=0. Apparently isn't.

Wonder what that value is and if it has a significance.

I think it must have a zero derivative at x=0 and the only reason we don't see it is because it's impossible to get a very high level of precision on how things are changing that close to 0 (on a normal-sized graph at least). We can try plotting x=0 to x=1 and seeing what happens then with smaller and smaller intervals.

To Borek: what function of [A]

_{0} and [B]

_{0} did you use to get equilibrium yield?

I always try to express [AB] in terms of these two and Δ[A

_{2}] (extent), but if [AB]=-2*Δ[A

_{2}] then when we square this expression due to the numerator of K

_{eq} we'll end up with 4*(Δ[A

_{2}])

^{2} (which could come from a positive) and this gives me finally wrong results.

Edit: Nevermind, I've got an expression that works to do the calculation (e.g. Δ[A

_{2}]=-0.75 when [A]

_{0} and [B]

_{0} are 2 and 1 respectively and Kc is 7.2, which I think is the correct solution to the first part of this prep problem). But the graph found is very different from yours - can we compare functions?