[Kstre]

What countries have the most interesting and toughest national competitions in chemistry?
I want to know some like the Poland, UK, Ukraine and not like USA, Canada...

[Wald_ron]

At the highshcool level, the hardest competition to get into is in hong kong, the space is extremely limited so the acceptance rate is very small and they accept only the best. I know there is one for highschoolers in brazil and germany as well as the US.

[Borek]

Hard to compare them without seeing problems.

I used some of the problems from the Polish Olympiad as problems of the week, but I selected rather specific ones - short and not requiring lengthy calculations.

[Kstre]

At the highshcool level, the hardest competition to get into is in hong kong, the space is extremely limited so the acceptance rate is very small and they accept only the best. I know there is one for highschoolers in brazil and germany as well as the US.

I think you misunderstood, I am looking for the most "difficult" tests. I kinda like the Polish Olympiad problems, and a little the UK tests, but I want to find more. The US question part can be done in 10 minutes (I admit that few questions are more difficult that the rest), the problem solving part isn't very difficult either, as the Polland for example is. Now, trying to find the China test (on english if possible ).