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163 questions from 1999–2025. Filter by year, type, difficulty, or starred-only; reveal answers progressively.
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All 163 questions
Excess sulfuric acid is added to solid sodium sulfite.
Solid calcium carbonate is heated strongly.
Lithium nitride is added to water.
Concentrated hydrochloric acid is added to a solution of sodium hypochlorite.
Solutions of lead(II) acetate and hydrobromic acid are mixed.
Excess concentrated ammonia is added to a solution of zinc chloride.
A mixture of acidified potassium dichromate and ethanol is heated.
Phosphorus is burned in excess oxygen.
Sulfur dioxide is bubbled into water.
Chlorine gas is bubbled through a sodium bromide solution.
Solutions of magnesium nitrate and potassium hydroxide are mixed.
A sodium thiosulfate solution is added to a suspension of silver chloride.
Bromine is added to a solution of ethylene in hexane.
Radium-226 emits an alpha particle.
Solid calcium hydrogen carbonate is heated to a very high temperature.
Solid potassium sulfite is added to a solution of hydrochloric acid.
Solutions of barium hydroxide and sulfuric acid are mixed.
A tin(II) chloride solution is added to an acidic solution of potassium dichromate.
Concentrated hydrochloric acid is added to a solution of sodium hypochlorite.
Nitrogen-16 undergoes β-decay.
Concentrated hydrochloric acid is added to solid manganese(IV) oxide.
Solutions of magnesium sulfate and barium hydroxide are mixed.
Solid barium peroxide is added to water.
A piece of copper metal is added to a solution of dilute nitric acid.
A solution of sodium thiosulfate is added to a suspension of solid silver bromide.
2-butanol is heated with a solution of acidified potassium dichromate.
Water is added to magnesium nitride.
Excess carbon dioxide is bubbled through a solution of calcium hydroxide.
Acidic solutions of potassium dichromate and iron(II) chloride are mixed.
Solutions of lead acetate and sulfuric acid are mixed.
Excess concentrated sodium hydroxide is added to a solution of zinc nitrate.
Fluorine-18 undergoes positron emission.
Concentrated nitric acid is added to iron(II) sulfide.
Acetic acid is added to solid calcium phosphate.
Small pieces of aluminum metal are added to concentrated sodium hydroxide solution.
Solutions of chromium(III) sulfate and barium hydroxide are mixed.
Concentrated hydrochloric acid is added to an aqueous solution of cobalt(II) nitrate.
Bromine gas is added to propene.
Solid sodium sulfide is added to water.
An aqueous solution of potassium triiodide is added to a solution of sodium thiosulfate.
Excess aqueous sodium fluoride is added to aqueous iron(III) nitrate.
Strontium-90 undergoes β-decay.
Excess carbon dioxide is bubbled through a solution of calcium hydroxide.
Ethanol is warmed gently with acidified potassium dichromate.
Excess carbon dioxide is bubbled through a suspension of calcium hydroxide.
Acidified solutions of cerium(IV) and iron(II) are mixed.
Solid calcium carbide is added to water.
Excess concentrated ammonia is added to aqueous nickel(II) nitrate.
Solutions of silver acetate and hydrobromic acid are mixed.
Gaseous hydrogen chloride is reacted with gaseous propene.
Solid ammonium chloride and solid calcium hydroxide are mixed.
Excess carbon dioxide gas is bubbled into a sodium hydroxide solution.
Sodium sulfite is added to a neutral potassium permanganate solution.
Aqueous hydrofluoric acid is placed on a piece of silica.
Chlorobenzene is heated with a mixture of concentrated nitric and sulfuric acids.
Iodine-131 undergoes radioactive decay.
Barium peroxide is added to water.
Acidic solutions of potassium iodide and potassium iodate are mixed.
A phosphoric acid solution is added to a solution of calcium hydrogen carbonate.
Solutions of lead(II) nitrate and potassium chromate are mixed.
Concentrated hydrochloric acid is added to an aqueous solution of cobalt(II) nitrate.
2-butanol is heated with concentrated sulfuric acid.
Solid calcium is heated in nitrogen gas.
Solid sodium ethoxide is added to water.
Solutions of magnesium sulfate and barium hydroxide are mixed.
An acidic potassium permanganate solution is added to a solution of sodium sulfite.
Radium-222 undergoes α-decay.
2-propanol is heated with concentrated sulfuric acid.
Solutions of hydrochloric acid and silver acetate are mixed.
A small piece of potassium is added to water.
Concentrated hydrochloric acid is added to a solution of cobalt(II) sulfate.
An acidified potassium dichromate solution is added to a tin(II) chloride solution.
Methyl ethanoate (methyl acetate) is reacted with a sodium hydroxide solution.
Carbon-14 undergoes β-decay.
Sodium peroxide is added to water.
Barium carbonate is treated with sulfuric acid.
Lithium metal is heated in nitrogen gas.
Concentrated hydrochloric acid is added to aqueous sodium hypochlorite.
2-methyl-2-propanol is mixed with cold hydrobromic acid.
Uranium-238 emits an α particle followed by a β particle.
A solution of hydrofluoric acid is added to a suspension of aluminum hydroxide.
Sodium iodide solution is added to a hydrogen peroxide solution.
Solutions of mercury(I) nitrate and hydrochloric acid are mixed.
Solid sodium sulfide is added to water.
Nitrogen dioxide is bubbled into water.
1,6-hexanedioic acid chloride is reacted with 1,6-hexanediamine.
Calcium sulfite is heated to a high temperature in a vacuum.
Solutions of sodium oxalate and acidified potassium permanganate are mixed.
Solutions of magnesium sulfate and barium hydroxide are mixed.
Gaseous dimethylamine and hydrogen chloride are mixed.
Toluene is reacted with chlorine in the presence of aluminum chloride.
Carbon-11 undergoes positron emission during a PET scan.
Aqueous silver acetate is mixed with aqueous sodium chromate.
Excess aqueous sodium oxalate is added to an aqueous solution of iron(III) nitrate.
Carbon dioxide is bubbled into an aqueous solution of calcium nitrate.
A solution of bromine in CHCl₃ is mixed with a solution of 1-butene in CHCl₃.
Uranium-235 is bombarded with a neutron to form one nucleus containing 54 protons and 83 neutrons plus a second nucleus and two neutrons.
Dilute solutions of cesium bromide and silver nitrate are combined.
Phosphorus(V) oxide is added to water.
Potassium chromate is added to dilute hydrochloric acid.
Solutions of hydriodic acid and hydrogen peroxide are mixed.
tert-Butanol (2-methyl-2-propanol) is heated with sulfuric acid.
Technetium-99 undergoes β-decay.
A strip of copper metal is heated strongly with concentrated sulfuric acid.
Solid dinitrogen pentoxide is added to water.
Lead(II) carbonate is added to hydrobromic acid.
Freshly precipitated manganese(IV) oxide is added to a solution of hydrogen peroxide.
Chlorine is combined with toluene (methylbenzene) in the presence of ultraviolet light.
Tritium (³H) undergoes radioactive decay.
Solutions of sodium sulfate and lead(II) nitrate are mixed.
Aluminum foil is added to concentrated sodium hydroxide solution.
Mercury(II) oxide is heated.
Sodium is added to 2-butanol.
Nitrosyl fluoride and boron trifluoride vapors are co-condensed.
Fluorine-18 emits a positron.
A solution of acetic acid (ethanoic acid) is added to solid cadmium hydroxide.
Phosphorus tribromide and water are mixed.
Hydrogen sulfide gas is passed into a solution of nickel(II) perchlorate.
A mixture of manganese(IV) oxide and concentrated hydrochloric acid is heated.
Calcium carbonate is added to aqueous hydrofluoric acid.
A mixture of benzene with concentrated nitric and sulfuric acids is carefully heated.
Aqueous solutions of propanoic acid and potassium cyanide are combined.
Solid silver chloride is treated with concentrated aqueous ammonia.
Aqueous sodium sulfite is heated with elemental sulfur.
Solid copper(II) sulfate is added to a potassium iodide solution.
Aniline is added to a cold acidified solution of sodium nitrite.
Uranium-235 undergoes nuclear fission to form barium-141 and krypton-92.
Chlorine gas is bubbled through cold aqueous sodium hydroxide.
Solid calcium carbonate is roasted.
Solutions of iron(III) nitrate and potassium thiocyanate are mixed.
Ethyl formate (ethyl methanoate) is heated with aqueous potassium hydroxide.
Nitrous oxide (dinitrogen monoxide) is heated with solid sodium amide.
Boron-10 captures a neutron to produce an alpha particle and another species.
Solid calcium oxide is added to distilled water.
Acidic aqueous solutions of potassium permanganate and iron(II) sulfate are mixed.
Gaseous ammonia and boron trifluoride are mixed.
Solid phosphorus(V) oxide is added to an excess of aqueous sodium carbonate.
Potassium hydroxide is added to a dimethyl sulfoxide solution of 1-bromobutane.
Fluorine-18 emits a positron.
Diiodine pentoxide is added to a barium hydroxide solution.
Sulfur dioxide is bubbled through an acidified solution of potassium permanganate.
Iron(III) oxide is heated with carbon monoxide gas at 1200 °C.
Aqueous hydrobromic acid is electrolyzed at platinum electrodes.
1-Butanol reacts with an acidified solution of potassium dichromate.
Oganesson-294 undergoes alpha decay.
Aqueous hydrochloric acid is added to a solution of sodium hypochlorite.
Aluminum foil is added to concentrated aqueous potassium hydroxide solution.
Metallic sodium is added to liquid ammonia in the presence of a trace amount of iron(III) nitrate.
Potassium tetrachloroplatinate is heated with two equivalents of aqueous ammonia.
Sodium tert-butoxide is added to 3-bromo-3-ethylpentane in N,N-dimethylformamide (DMF) solution.
Cobalt-57 undergoes radioactive decay by electron capture.
Aqueous ammonia and acetic acid are mixed.
Sodium iodate is added to an excess of hydriodic acid.
Manganese(IV) oxide is added to concentrated aqueous hydrochloric acid.
Propyl benzoate is heated with aqueous sodium hydroxide.
Calcium oxide and graphite are heated to 2200 °C.
Iodine-124 undergoes radioactive decay by electron capture.
Carbon dioxide is bubbled through a saturated solution of barium hydroxide.
Potassium permanganate is mixed with iron(II) sulfate in dilute sulfuric acid.
Solid silver chloride is added to concentrated aqueous ammonia.
Phosphorus trichloride reacts with potassium chlorate.
Para-xylene (1,4-dimethylbenzene) is heated with a mixture of concentrated nitric and sulfuric acids.
Fluorine-18 emits a positron.