861 past contests
Topic 6 · True or false: a decomposition reaction may involve both chemical and physical changes
Topic 6 · True or false: a decomposition reaction always breaks a single reactant into two or more products
Topic 1 · Problem of the day: verifying an antacid tablet's caco3 content against its label claim, via co2 evolved
Topic 7 · Electrons involved in reducing sulfate ion to sulfide ion
Topic 20 · Concentration of lithium sulfate dissolved to a given volume
Topic 26 · Identifying a carbonyl-containing isomer of c4h8o
Topic 29 · Identifying the element with highest electron affinity in an unrecorded comparison set
Topic 30 · Riddle: lithium, the lightest metal, used in the first synthetic nuclear reaction
Topic 2 · True or false: oxide ion has higher polarizability than sulfide ion
Topic 2 · True or false: bromide ion has higher polarizability than chloride ion
Topic 2 · True or false: oxide ion has higher polarizability than fluoride ion
Topic 2 · True or false: ethene has four sigma and two pi bonds
Topic 2 · True or false: methanal has one pi bond and three sigma bonds
Topic 2 · True or false: chloroethene has one pi bond and five sigma bonds
Topic 28 · True or false: no two electrons can have the same energy (pauli's principle)
Topic 28 · True or false: no two electrons in the same orbital can have the same spin (pauli's principle)
Topic 23 · Riddle: butanol, a four-carbon alcohol with an optically active isomer
Topic 28 · True or false: no two electrons can occupy the same subshell (pauli's principle)
Topic 20 · True or false: smoke is an example of a solid-in-gas solution
Topic 20 · True or false: air is an example of a gas-in-gas solution