USNCO Preparation

I was going over past exams and I came across problem #36 on the 2018 USNCO locals, which stumped me when I came across it. I knew acid/base equilibrium problems were one of my weak spots and I spent lot of time refining that section (I use Atkins 7th edition) but when I checked the solution for #36, it involved a really long multi-step solution where the molar solubility (MS) was assigned to a variable and you had to use several relations and equations to solve for the ratio between the final MS and the initial MS. Are there any tips for how to approach longer problems such as these, and how to recognize when to use these approaches? Are problems like these a trend or an exception in the competitions?  Thanks for the help!   *Link to #36 Solution: https://docs.google.com/document/d/1AEG2u8bZ_Buv4rBzwDTaTSKZJ6urx0LKs038S87Zs9U/edit  ... View more

How can I volunteer to annotate exam solutions? I've emailed usnco@acs.org frequently about it, but I haven't been able to get a response.  ... View more

This forum is open to anyone interested in the U.S. National Chemistry Olympiad (USNCO). Please feel free to share your favorite resources, ask questions of our volunteers, or share comments/suggestions for annotated solution guides in the relevant forums. You only need an ACS ID to login and join the conversation (a member number is not required). Before you begin, please review these guidelines. ACS does not directly endorse any resources shared here that were not produced by the ACS. For details of the competition in your local area, such as exam dates and times, contact your coordinator. In the U.S., you can lookup your coordinator here. For U.S. citizens living outside the country, email USNCO@acs.org If you need any assistance, please contact our moderators through messages here or at USNCO@acs.org ... View more

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Here you can share with our editor and volunteers any comments, suggestions, or corrections you have after reviewing the annotated solutions shared on the USNCO Exams Page. Please start your comment with the exam and year you are referencing - i.e. Local 2020, National 2019. ... View more