CODS Competitor's Guide

By Nicolai Bogo Stabell (Stabell#6680) & Kwanwoo Park (fizzest#0001)

Version 1.1 (November 5th, 2021)

Author Note: The guide is an ambitious attempt to cover everything that a competitor needs to know about our competition structures. This guide is written as detailed as possible for the competitor to reference.

Jeremy's Note: The guide on the website (you're reading it!) is not guaranteed to be as complete or up-to-date as the google docs. As such, please check the Google docs.


With the beginning of the 2021-22 season, CODS will adopt a new system, taking into consideration what we've learned from our past competitions. CODS will host four competitions every season, which will begin in Autumn and end during the summer. Each competition will have its own unique characteristics, and will be widely accessible to competitors at any skill level.

The Tier System & Syllabus

New to the 2021-22 season, CODS is introducing a new tier system. Our tier system is inspired by the one used in the United States of America Computing Olympiad (USACO). The goal of the tier system is to create more differentiation in our competitions, allowing more people to participate at a level that is appropriate for them. Differentiation has not previously been possible in the old competition structure, in which competitions' difficulty tended to increase throughout the season, leading to a gradual decrease in participation.

We define three new tiers, Bronze, Silver, and Gold.

Each tier will have different exams for competitions (with the exception of SOCC) that correspond to a set difficulty. In the following, we describe the syllabus of the three tiers for competitors to study. CODS will be dedicating much of the website development this year to providing high-quality learning materials for the specific topics illustrated below, similar in nature to USACO guides.

Bronze Tier

The Bronze TIer is the entry tier at which every person competing in a CODS Competition begins. The average difficulty and problem-solving level for the bronze tier is around USNCO Locals. We want all competitions to be somewhat challenging for newcomers, althoguh the concepts involved should be relatively straightforward.

Analytical Chemistry
  • Acid and Base (strong, weak, and polyatomic).
  • Choice of indicators.
  • Redox (Permanganate, Iodometric).
Qualitative AnalysisInorganic
  • Cations (see docs)
  • Anions (see docs)
  • Flame colors (Li, Sr, Cu).
  • Amphoteric oxides (Zn, Sn, Pb, and Al).
  • Alkene, halogenoalkane, alcohol, aldehydes, arboxylic acids.
  • Identification of aromatic compounds.
  • Identification of chromophore.
  • Dyes: colour vs structure.
  • Beer's Law
General Chemistry
  • Counting of nucleons.
  • Isotopes.
  • Types of radioactivity.
  • Radioactive decay (alpha, beta, and gamma).
  • Nuclear reactions (alpha and beta decay, positron emission, electron capture, gamma emission, and spontaneous fission).
Chemical Calculations
  • Balancing equations.
  • Stoichiometric calculations.
  • Mass and volume relations
  • Mass, volume, and mole percent.
  • Emperical formula.
  • Avogadro's number.
  • Concentration calculations.
Inorganic Chemistry
Periodic Trends
  • Main group elements (see docs).
  • Main group trends in physical properties (melting point, boiling point, metal character, magnetic properties, and electrical conductivity)
  • Reactivity series (K, Na, Ca, Mg, Al, C, Zn, Fe, Sn, Pb, H, Cu, Hg, Ag, Au).
Chemical Bonding
  • Bond types (polar/nonpolar and covalent/ionic bonds).
  • Electronegativity (determine type of bond: ionic, polar, and nonpolar).
  • Lewis structures.
  • Octet rule.
  • Formal charges.
  • VESPR (no more than four electron pairs about the central atom with the central atom exceeding the "octet rule").
  • Delocalization and resonance.
Inorganic Reactions
  • Combination reactions
  • Decomposition reactions.
  • Precipitation, single and double-replacement reactions.
  • Redox reaction (neutral, alkaline, and acidic).
  • Main group and transition metal compounds.
Groups 1 and 2
  • Trend in Reactivity of (heavy elements more reactive).
  • Products of reaction (water, halogens, and oxygen).
  • Basicity of oxides.
Groups 13-18 and Hydrogen
  • Binary molecular compounds of hydrogen, formulas, and acid-base properties (see doc).
Group 13
  • The oxidation state of boron and aluminium in their oxides and chlorides is +III.
Group 14
  • Si's oxidation state in its chloride and odixe is +IV.
  • The +II and +IV oxidation states of carbon, tin, and lead.
Group 15
  • Oxides of nitrogen (see doc).
  • Redox properties of nitrogen (see doc).
Group 16
  • The +IV and +VI oxidation states of sulfur, reaction of thier oxides with water, and properties of their acids.
  • Reaction of thiosulfate anion with iodine.
Group 17 (Halogens)
  • Reactivity and oxidant strength decrease from fluorine to iodine.
  • Acid-base properties of the hydrogen halides.
  • The oxidation state of fluorine in its compounds is -I
  • The -I, +I, +III, +V, and +VII oxidation states of chlorine.
  • Reactions of halogens with water.
Group 18
Transition Elements
  • Common oxidation states of common transition metals (see doc).
  • The insolubility of Ag, Hg, and Cu in HCl.
  • M^2+ arising from the dissolution of the other metals in HCl.
  • Permanagante and Dichromate are strong oxidants in acid solution.
Coordination Chemistry
  • Definition of coordination number.
  • Writing equations for complexation reactions given all formulas.
  • Formulas of common complex ions (see doc).
Organic Chemistry
  • Drawing structures (Condensed Formula, Kekule & Skeletal Structures).
  • DBE (double bond equivalent).
  • Properties, isomerism (structural and stereoisomerism).
  • Substance classes (see docs).
  • Types of organic reactions (see docs).
Physical Chemistry
  • Ideal gas law.
  • Dalton's law.
  • First Law (Concept of systems and surroundings, Energy, Heat, and Work).
  • Enthalpy (Relationship between internal energy and enthalpy).
  • Enthalpy is a state property (Hess's law).
  • Reaction enthalpy (use of standard formation enthalpies).
  • Reaction entropy and disorder.
  • Reaction Gibbs energy and definition (see docs).
  • Using Gibbs to predict the direction and spontaneity.
  • Relationship between Gibbs and equilibrium constant K.
  • Equilibrium constant (homogeneous and teterogeneous).
  • Reaction quotient (Q/Y).
  • Relating equilibrium constants of pressure (K_p) and concentration (K_c).
  • Le Chatelier's principle.
  • Solubility constant (product) definition (Ksp).
  • Calculation of solubility in water from Ksp.
  • Common-Ion Effect.
  • Complex formation constant (K_K)
  • Simple coupled equilibria.
  • Arrhenius definitions of acids and bases.
  • Bronsted-Lowry definitions.
  • Conjugate acids and bases.
  • pH, Kw definition and K_a or K_b as a measure of acid and base strength.
  • Acidity or basicity of ions.
  • Buffer system and capacity.
  • Calculation of pH from pK_a (weak acid).
  • Calculation of pH of a simple buffer solution.
  • Simple knowledge of amphoterism and their pH (see doc).
Chemical Kinetics
  • Factors affecting reaction rate.
  • Reaction coordinates and the basic idea of a transition state.
  • Differential rate laws.
  • Concept of reaction order.
  • Rate constant definition.
  • 0, 1, and 2 order reactions and their integrated rate laws (single reactant).
  • Dependence of concentration on time.
  • Concept of half-life.
  • Relationsihp between half-life and rate constant.
  • Determine reaciton order (method of initial rates and graphs of integrated rate laws).
  • Reaction mechanisms (concept of molecularity, rate-determining step).
  • Basic concepts of collision theory.
  • Arrhenius's law.
  • Catalysts and how it affects activiation energies (homogeneous, hteterogeneous, and biocatalysts).
Mathematics Skills
  • Solving quadratic equations.
  • Use of logarithms and exponentials.
  • Solving simultaneous equations with 2 unknowns.
  • Elementary geometry such as Pythagorean's theorem.
  • Plotting graphs (normal, exponential, and logarithmic).

Silver Tier

The Silver Tier is a tier higher than the Bronze Tier. The average difficulty and problem-solving level for the silver tier should be between USNCO Nationals Part II and WCC. It can involve any topics in the bronze tier and the advanced topics listed below, such as Organic Chemistry (althoguh limited to knowledge you can find in Klein's Organic Chemistry).

Analytical Chemistry
SpectroscopyMass Spectrometry
  • Recognition of molecular ions.
  • Recognition of fragments with the help of a table.
  • Recognition of typical isotope distribution.
  • Complexometric titrations (EDTA).
  • Bragg's Law.
  • Interpretation using a table of frequencies (see doc).
  • Recognition of hydrogen bonds.
  • General concepts (chemical shift, integration, spin-spin coupling, and coupling constants).
  • Interpretation of a simple 1H spectrum
  • Identification of o- and p-disubstituted benzene.
  • Interpretation of simple spectra of 13C (proton decoupled) and other 1/2 spin nuclei.
Inorganic Chemistry
Periodic Trends
  • Transition metal elements (see doc).
The Atom
  • Shape, orientation, and Quantum numbers (n, l, m) of s, p, and d orbitals.
  • Radial and angular nodes.
Chemical Bonding
  • Valence bond theory (see doc).
  • Molecular orbital (MO) diagram (2 period).
  • Bond orders.
  • Para- and diamagnetism.
Inorganic Reactions
  • Comproportionation and disproportionation reactions.
  • Special bonding (3c-2e) using molecular orbital theory.
  • Simple metal complexes.
Group 1 and 2
  • Properties of hydrides.
  • Other compounds, properties, and oxidation states.
Group 13-18 and Hydrogen
  • Other properties.
Group 13
  • The acid-base properties of aluminum oxide/hydroxide.
  • Reaction of boron(III) oxide and boron(III) chloride with water.
  • Other compounds, properties, and oxidation states.
Group 14
  • The acid-base and redox properties of the oxides and chlorides.
  • Other compounds, properties, and oxidation states.
Group 15
  • Phosphorus (+III, +V) oxide and chloride, and their reaction with water.
  • Redox properties (see doc).
  • Bi(+V) and Bi(+III).
  • Other compounds, properties, and oxidation states.
Group 16
  • Other compounds, properties, and oxidation states.
Group 17
  • Mononuclear oxoanions of chlorine.
  • Reaction of chlorine oxides with water (see doc).
  • Other compounds, properties, and oxidation states.
Group 18
Transition Elements
  • Colors of ions in qaueous solution (see doc)
  • Chromium hydroxide and Zinc hydroxide are amphoteric and the other +2 oxides/hydroxides listed in the doc are basic (see doc).
  • pH dependence of products of permanganate acting as oxidants.
  • Interconverstion between chromate and dichromate.
  • Other compounds, peroperties, and oxidation states.
Coordination Chemistry
  • Formulas of other complex ions.
  • Ligand field theory (eg and t2g terms, high/low spin, and color).
  • Color of complex compounds (spectrochemical series).
  • Para and diamagnetic.
  • Isomerism (Structural, Coordination, Linkage, Geometric: cis/trans, planar, octahedra, enantiomers).
  • Unit cell (cubic).
  • Coordination number.
  • Packing type (aba, abc, abcd).
  • Solid structures (metals, NaCl, CsCl, ZnS).
  • Density for metals and salts.
Organic Chemistry
  • IUPAC nomenclature, including E/Z and R/S stereoisomerism.
  • Draw stereochemically unequivocal structures for organic molecules.
  • Account for optical activity and the difference between enantiomers, diastereomers, and meso compounds.
  • Differentiate between SN1/SN2 and E1/E2 reactions.
  • Draw resonance forms for cations and anions.
  • Predict reactivity of organic molecules based on structure, resonance, and inductive effects.
  • Draw reaction mechanisms for simple and polar reactions.
  • Suggest syntheses in one or more steps of simple, organic molecules.
  • Design simple reactions with common functional groups.
  • Apply inorganic reagents for oxidation, reduction, and subsittution in synthetic planning.
  • Account for structure and reactivity of carbohydrates, amino acids, lipids, and nucleic acids.
Physical Chemistry
  • Born-Haber cycle for ionic compounds.
  • Bond enthalpies (definition and use).
  • Electromotive force (definition).
  • Galvanic Cells.
  • Notation of cell diagrams.
  • Standard electrode potential.
  • Nernst equation.
  • Relationship between Gibbs and electromotive force.
  • Electrolysis.
  • Corrosion.
Acids and Bases
  • Lewis acids and bases (hard and soft).
  • MCB (not too complex).
  • Bjerrum plot (reading).
Chemical Kinetics
  • Steady-State approximations (maxiumum of 4 steps, where an equilibrium step counts as 2 steps).
Mathematics skills
  • Use of math skills from the bronze tier to derive simple expressions.
  • Single-variable Calculus (basic derivatives and integrals).
  • Taylor series.
Mathematical equations may be provided for questions.

Gold Tier

The Gold Tier is the highest proposed tier for CODS Competitions. The average difficulty and problem-solving level for the gold tier should be between IChO to Mendeleev (IMChO) difficulty. It should involve a more sophisticated level of advanced topics and should be very challenging. Therefore, teh syllabus for gold tier is the current or last year's IChO and IMChO preparatory problems and exams.

Promotion, Demotion, Decay

In each competition, promotion and demotion can occur.

TierPromotion RequirementDemotion Requirement*Decay

For eample, Silver partticipants who palce within the Top 10% of any competition will be promoted to the Gold tier. Additionally, silver participants who do not compete in four consecutive CODS competitions in a row will be subjected to demotion (decayed) to the lower tier.

If the number of participants in a tier resutls in a fractional number of participants to be promoted or demoted, teh number is rounded to the nearest integer.

*In the case that the total number of partiicpants in a tier who took the competition's exam is 9 or lower, no participants will be demoted.

*In the case that the total number of participants in a tier who took the competition’s exam is 9 or lower, no participants will be demoted.


All competitions will ahve a Main round for all participants and a Final round for participants who do exceptionally well. All participants who make the TOp 10 or the top 25% in their tier, whichever is larger, will be qualified for the final round. Participants with score(s) within 2% of the last participant who received promotion, demotion, or round qualification will also recieve it. Final round participants who meet the promotion requirement as select overall winners will be promoted after the competition.

Summer Chemistry Olympiad (SChO, 2021)

SChO is our summer competition, an IChO-style free-response exam for all three tiers. Participants for this year will be able to choose the tier that seems appropriate to them. This is true only for SChO 2021.

Tier# of Questions (Time)DifficultyPromotion RequirementDemotion Requirement
Bronze4 (120 min)Introduction to competitive chemistry15%-
Silver7 (210 min)Slightly harder than WCC Part II10%15%
Gold9 (300 min)IChO / Mendeleev Olympiad Difficulty-30%

We hope that this year’s SChO will give the participants a good idea in terms of what to expect for future competitions. Participants may choose to move to a more suitable tier that is appropriate to their skill level after the competition.

Autumn Chemistry Online Tournament (ACOT)

The first competition of each year will be our autumn competition, whcih tests on your skill of both speed and accuracy.

In the main round, all participants will take a 20-question multiple choice exam in up to 60 minutes. Questions in the multiple choice exam may have multiple answers. Both speed (time it took to complete the exam) and accuracy will be taken into consideration to your score. Guessing will be penalized. More information about ourmathematical model can be found in the ACOT 2021 Rulebook.

The final round will be 4 free response questions with multiple parts. Each tier will have an Organic, Inorganic, Anlytical, and Physical Chemistry question. The participants will have up to 120 minutes to complete the round. The score for this round will similarly be calculated from the time taken and the score.

Winter Chemistry Competition (WCC)

In the main round of our winter competition, participants will be teaming in teams of four in a three round competition. You may team with team members from different tiers; however, your team will be taking the exam of the highest tier member.

In the first round, the team will split up and take a 90 minute individual exam. In the second round, bronze and silver tiems will work for 120 minutes in a closed-book team exam; gold tiems will work together for 4 hours in an open internet exam (based off of the Open Round from SOCC '21). Both round and all tiers will consist of four questions, one of each of the following topics: physical, inorganic, organic, and analytical chemistry. To see what type of questions gold participants are expected to be asked during the open round, refer to our SOCC '21 Open Round exam.

The final round will be Cleaving Bonds, in which your team will be given twelve rounds to solve, each containing three short-answer questions of similar difficulty. All teams will begin from round 1 and progress at their own pace through the rounds. Once a round has been submtited, you will gain access to the next round and will not be able to work on previous rounds. Rounds will be graded on-the-spot and after a 90-minute grace period; once the first five teams have completed round 12, the compettion will end immediately.

All of the members in the top 3 will get promoted to Gold, regardless of their current position. The members of the winning teams for Silver and Gold will be invited to the CODSChO mock IChO exam. All other teams that have met the promotion requirement will be promoted to their next tier.

Spring Open Chemistry Competition (SOCC)

SOCC will be whenever the mock USNCO is held.

For the main round, all participants will take the same USNCO National Part I style (60 multiple-choice questions, 90 minutes) exam.

The top 25% scorers will be invited to the final round, a USNCO National Part II style (8 free-response questions, 105 minutes) exam, and partiicpants will be awarded as shown below:

AwardsHonorsHigh HonorsDamper
Top %1673
GradingPart I ScorePart I Score × 1.25 + Part II ScorePart I Score × 1.25 + Part II Score
PromotionPromotion to next tierPromotion to GoldGold + Invited to CODSChO

Summer Chemistry Olympiad (SChO, 2022+)

The Summer Chemistry Olympiad will be a month-long competition session where participants will be given the opportunity to learn new material, and apply them in a competitive olympiad setting. At the start of the week, all tiers will be provided the same theme (Food, Coffee, Enzymes, Photography, Farming, etc.) but different advanced topics for each tier (these advanced topics will be topics not contained in the tier’s syllabus. For example, Bronze may have steady-state approximation, Silver may have chemical potential, etc.)

At the end of the week, participants will be given one extended free-response question that utilizes the advanced topics with the set theme. These questions will test how well the participant has learned to utilize and apply the advanced concepts they’ve learned throughout the week.

For gold tier participants, SChO will mainly deal with advanced topics that will likely be present in CODSChO. At the end of the fourth week, the individual’s scores across the four weeks will be averaged and promotion/demotion will occur as shown in 2.4.

The CODSChO exam will be a mock IChO exam that is extremely difficult for even those competing at the highest level. It will occur in two weeks before the opening IChO ceremony. Participants who score high on this exam will receive prizes and awards. The following participants are invited to take this exam: IChO qualifiers (in the current year), IChO medalists (from any year), qualifiers from other CODS competitions (such as WCC top teams), and gold medalists who have competed in more than three competitions during the season.


Testing for the 2021-22 season will be slightly different from the previous year. We will be providing 48-hour flexible testing blocks over which competition rounds can be taken (in comparison to fixed times), and we expect competitions to be much less of a time commitment for participants in comparison to our previous competitions. There will be three testing blocks on Saturday and two testing blocks on Sunday. Some competitions, such as Cleaving Bonds or CODSChO, may be limited in time slots due to the nature of the competition.

Participants will be required to have a functioning webcam (for workspace) and a phone or scanner to scan their hand-written answers for submission. Video proctoring will not be done on Discord, but ont he testing website itself. Multi-accounting is considered cheating and will be a network-bannable offense. While we cannot go over the handful of cheating protocols and new tools to detect cheating for obvious reasons, testing security is a big focus in CODS competitions and any evidence that confirms cheating will be taken seriously and punished. The specifics of rules in each competition will be introduced in much more detail later on.

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