Advice for USNCO nonbeginners

Initially written by our staff member llamachemist (Anugrah Chemparathy, 2020 IChO gold medalist, we have tried to preserve the guide as it has initially been written. You can look at the original source here.

This advice is only relevant to people who can comfortably solve every problem on a pre 2017 USNCO (and most of the newer ones!) or have done all the past USNCOs (locals and nationals). If neither of these are true, then you should return to this document at a later time.



In my opinion, almost all of the non recent USNCOs are boring. Especially in your second year of preparing for the Chemistry Olympiad, you’ll want to find a new way to learn. Here is my not very hot take: reading anything beyond Atkins/Zumdahl + Klein1 is completely unnecessary for USNCO (it's not a hot take because everyone agrees with me). Even to get into IChO, you don't need anything more than Atkins/Zumdahl + Klein + chapters 27-38 & 40 of Clayden2.

I really don't understand why everyone keeps buying copies of Atkins Physical Chemistry, Housecroft Inorganic, or Voets Biochemistry to prepare for USNCO or IChO when a simple glance at the contents of either will make it incredibly obvious how useless they are for both IChO and especially the USNCO. Even for the most specialized topics at IChO, you’re better off learning them from online (ex. ChemLibre) than in a textbook. By the end of my senior year I had spent more time reading physics textbooks (just for fun) than I had chemistry textbooks. Here is a quote from a noted Russian IChO gold medalist:

R: I didn’t buy a book to prepare for the Olympiads except for Albert L. Lehninger’s works. There are plenty of resources online.3

The real secret to succeeding (in the Chemistry Olympiad) is to build your problem solving ability. The best way to do this is to practice solving challenging problems. Over the years I did a lot of problems. Here are my opinions on some of the problems I did, and some of the problems I did not do.

Note that what I’ve listed below is pretty brief and not necessarily a full endorsement or indictment of certain years of problems. My biggest piece of advice is to look through all the problems (not just the ones I’ve listed in each year's description, and PICK WHAT LOOKS INTERESTING. I didn’t list every single problem I liked since that would take forever, so don't stick to this list! And also don't try to meticulously do all of them. That's a waste of time.

One more time: I do not recommend you try to grind all of these problems. You will burn out (source: been there even though I did just a fraction of them). Just do what seems interesting.

Prep Problems

IChO Preparatory Problems are great for practice. Here are some recent years sorted by how interesting/difficult I think they are in general (not counting organic which varies in quality/difficulty).

S-tier: aka very very difficult + not applicable to USNCO

  • 2013 - infamous Russian IChO with very hard questions. Generally not applicable for USNCO. The few that I would recommend: #8, 9, 13, 15 although they are just as difficult as the rest (but mildly more applicable to USNCO/common IChOs)

    • You can return to these later when you are more experienced. Avoid #6, 10, 17 until the very end since these problems are impossible by even the best (I myself don't think I can do either of #6 or 17 without help)
  • 2015 - Another infamously difficult year. None of these questions are really helpful for USNCO. Don't waste your time on them until you are preparing for camp.

A-tier: very good for USNCO

  • 2008/2016 - (both years have the same set of preparatory problems) - all round very good problems many of which are extremely relevant to USNCO. I highly recommend that you do all of them except #22.
  • 2019 minus the two special MO problems at the beginning (some of the polymers stuff is optional too, but some of it is still very good even if you don't want to study anything related to polymers too seriously: see #13)

B-tier: decent for USNCO

  • 2018 minus the ion exchange resin stuff (although it's actually super intuitive so #10 and #11 could be fun to try if you just want to try some reading abilities + chem and I mean this unironically. #18 is also skippable)
  • 2012 except for #21-22. Overall these problems are decent quality but a little easier than the modern USNCO.
  • 2001 - There are a couple good problems sprinkled throughout. Just skim through them and see what looks interesting to you.

B minus-tier: idk :?

  • 2007 - Most of these questions are not relevant to USNCO. However I am a fan of the following questions: #5,12,13,17
  • 2014 - Also mostly not useful to USNCO. Some of the ideas in them are good for practice even if they won't show up on USNCO (like particle in a box): #2,3,4,8,10,11,14
  • 2017- These questions and the corresponding IChO are exceptionally easy compared to most of modern IChO. Very few of them are worth doing in the traditional problem sense, but they could make for useful quick warm up exercises.
  • 1996 - Some of these might interest you. Skim them and see what looks cool.

C-Tier: Mostly useless except for beginners

  • 2020 - The first half of the non organic problems in this year are very easy inorganic. The few subparts that are worth doing within these questions are ideas that are probably better off learning from other years of preps. The second half are not really useful for USNCO. Some problems at the end are creative/interesting however: #20, 22-25

F-tier: Dont do these

  • Anything from before 2012 (except for 2008! And some of the 2007)

Of course take this advice with the commentary given at the top of the page: look through anything you want and do questions which interest you. Don't try to adhere to the questions listed here and end up getting stuck in a grind.

Foreign Olympiads

Some olympiads from other countries have good quality questions. Here are links to some of the famous olympiads along with my opinions of them.

-   Except for the organic, these are almost all easier than USNCO
-   Generally around USNCO level although these questions are usually much less creative. (The organic is much harder than USNCO of course)
  • Mendeleev: Restored (See the left column)
-   Don’t do these unless you’re very experienced (like at the end of the year, or maybe when you are a returning camper)

-   Organic and Biochemistry have no relevance to USNCO.

-   Inorganic is usually much beyond USNCO difficulty, but generally very fun.

-   physical chemistry is usually boring bashing(although occasionally there are some good ones) of some random equation or data they give you and frequently easier than USNCO. These questions are often soul sucking. 0/10 would not recommend.

-   Analytical difficulty varies a lot. Some of them are extremely easy, while others are very interesting and bring added problem solving to ideas which are useful for USNCO (see 2015 Tour 1 #4). These questions can be extremely challenging, but if you are already well versed with USNCO, I think that they are good exercises in problem solving.
  • INChOs
-   Recent: [](

-   Old: [Pre 2008](

-   Generally these questions are either easy or impossible due to being extremely weird. I don't really enjoy them, but some of them could be acceptable for USNCO practice (2002 #5, 2003 #1)


Some of the IChOs are good, and some of them are bad for USNCO practice. Here’s a summary of my thoughts on some of them.

S-Tier: Probably too hard for most people

  • 2013 - Basically everything in this test is hard (but not all!). Some problems are fun exercises anyways although you might struggle on them: #5, 6
  • 2015 - Another tricky IChO. Some questions are downright unreasonable for even the best campers. (see #6). I found all the problems really enjoyable however (including the biochemistry!). In order of increasing difficulty: #2, 3, 5, 7, 8, 1, 4, 6

A-tier: very good for USNCO (ordered in decreasing utility, 2016 is the best)

  • 2016 IChO - My favorite IChO. The style of the questions is very similar to USNCO, and some of the questions were very similar to USNCO 2018/19.
  • 2008 IChO - Quite difficult, but also more related to USNCO than 2013 and 15 so I put it in this category. Would probably make a good mock camp test if you tried it in 2 hours.
  • 2012 IChO - Do it in 3 hours and it will be a fun challenge

B-tier: decent practice if you have time, but you’re probably better leaving this off till next year

  • 2014 IChO - The non organic problems are decent. Try them if you want
  • 2018 IChO - Some of the problems are interesting. This was probably one of the harder among the “easy” IChOs, but mostly because the questions were so unusual in style. I like the following problems: #1, 2, 5. #4 is a good exercise in reading (unironically) and can be done without any understanding of ion exchange resins.

C-tier: Too easy but they’re still IChOs so whatever I guess

  • 2017 was a boring year
  • 2011 - #3 is good (don't worry if you’ve never done anything with harmonic oscillators before. Everything can be figured if you read all the information/equations they give you in the question and then are extremely scrupulous with making your units work out.) #5 looks like it could be interesting, but I haven't done it.
  • 2010 IChO - An infamously easy IChO that is decent for practice of some basic USNCO ideas. #2 is straightforward computation relevant to the older USNCOs. #3 is a good basic iodometry question for beginners.
  • 2009 IChO - #2 was the first ICHO question I ever did and I am quite fond of it. #6 is a decent question for people learning CFT

F-tier: Don’t do these (except for certain questions)

  • Anything before 2012 is generally not worth doing seriously. NOTE however that some of them have potentially interesting questions (for example the questions listed from 2009-11 above). You can skim through the old tests and see what interests you.
  • Some older years actually have very good problems (for example 1996!) They’re just few and far between so you shouldn’t try to do all of them or anything.

  1. Referencing to Atkins' Chemical Principles and Klein's Organic Chemistry
  2. Referencing to Clayden's Organic Chemistry.
  3. Source is here.

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