861 past contests
Topic 41 · Four naturally occurring redox processes: combustion, decomposition, corrosion and rusting
Topic 22 · Riddle: ethanoic acid, precursor to cellulose and polyvinyl acetates
Topic 7 · True or false: if oxidation numbers in a compound sum to zero, the compound is neutral
Topic 7 · True or false: a +2 oxidation-number sum in a polyatomic ion means it must be a cation
Topic 7 · True or false: zero oxidation number implies the species is in its elemental form
Topic 3 · True or false: an acid and the conjugate base formed from that weak acid constitute a buffer system
Topic 3 · True or false: a lower-pka weak acid always forms a more acidic buffer than a higher-pka one
Topic 3 · True or false: a weak acid and a weak base alone constitute a buffer system
Topic 26 · Problem of the day: five optically-active isomers of c6h13br
Topic 12 · Molarity of naoh needed to neutralize a given volume of hcl
Topic 19 · Empirical formula tg4 from masses and atomic masses of two elements
Topic 1 · Moles of water formed from complete combustion of one mole of propane
Topic 7 · Reduction half-reaction of permanganate to mn2+
Topic 7 · Reduction half-reaction of fe3o4 to iron metal
Topic 7 · Oxidation half-reaction of sulfite to sulfate
Topic 6 · Ksp expression for magnesium phosphate
Topic 6 · Ksp expression for aluminum sulfate
Topic 6 · Ksp expression for lithium carbonate
Topic 29 · True or false: atomic number increases proportionally with atomic size
Topic 29 · True or false: sr2+ and as3+ are isoelectronic