861 past contests
Topic 7 · Oxygen has oxidation state 0 in the ozone molecule, an elemental allotrope
Topic 1 · Mass of magnesium carbonate heated to form a given mass of magnesium oxide
Topic 28 · 8 electrons occupy the n=3 shell of the ca2+ ion
Topic 9 · Sum of stoichiometric coefficients in balanced b2br6+hno3→b(no3)3+hbr
Topic 28 · Cobalt has 3 unpaired electrons in its 3d subshell, via hund's rule
Topic 19 · Determining a molecular formula (c9h8o4) from molar mass and the mass of carbon present
Topic 9 · Sum of stoichiometric coefficients in balanced nh3+o2→n2+h2o
Topic 29 · Sulfur has the lowest first ionization energy among cl, p, and s
Topic 33 · Metallurgy as the study of metals, their extraction, and their properties
Topic 27 · Number of mass-spectrum peaks for a tetra-atomic molecule of an element with two isotopes
Topic 2 · Sp² hybridization of the carbon orbital in the bicarbonate ion hco3-
Topic 11 · Volume ratio of methane to oxygen from a 2:1 mass ratio, via avogadro's law
Topic 2 · Predicting the formula y2x3 from outer-shell electron counts of 6 and 3
Topic 9 · Sum of stoichiometric coefficients in balanced n2+o2+h2o→hno3
Topic 23 · Phenol's acidity from inductive electron-withdrawal and resonance-stabilized phenoxide
Topic 1 · Identifying cl2o5 as the chlorine oxide with a ~1:1 cl:o mass ratio
Topic 1 · Finding the atomic mass of b in ab2 from molar mass and a's atomic mass
Topic 9 · Sum of stoichiometric coefficients in balanced nh4no3 decomposition
Topic 35 · Riddle: calcium nitrate, a soluble salt of a reactive group 2 metal
Topic 24 · Ethene polymerizes only with a catalyst/initiator, not pressure alone (true/false)