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This chemistry trivia quiz has 129 free questions with answers and starts with the fundamentals (atoms, the periodic table, bonding, acids and bases, redox, states of matter) and works up to organic chemistry: alkanes and their isomers, alkenes and alkynes, functional groups from alcohols to esters, Kekulé's benzene ring, Markovnikov's rule, Grignard reagents and the Diels-Alder reaction, plus the people who built the field, from Wöhler and Liebig to Perkin and Pasteur. Questions range from easy ones any science student can handle to hard ones aimed at people who have actually sat an organic chemistry exam. Every question shows its difficulty, so you can pull an easy round for a classroom or a hard round for a lab-group quiz night. Every answer has been checked against a primary reference and each question carries its citation.
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Q 01Which chemist created the first widely accepted periodic table?
Dmitri Mendeleev
Dmitri Mendeleev, a Russian chemist, is credited with creating the first widely accepted version of the periodic table in 1869. He arranged the elements by atomic weight and predicted the properties of undiscovered elements.
Q 02Beyond solid, liquid and gas, what is usually counted as the fourth state of matter, the stuff of stars and lightning?
Plasma
Plasma is an ionised gas of free electrons and ions that answers to electric and magnetic fields; William Crookes floated the idea of a fourth state in 1879.
Q 03What type of chemical reaction absorbs heat energy from its surroundings?
Endothermic
Endothermic reactions absorb heat energy from their surroundings, causing the temperature of the surroundings to drop and often feeling cold to the touch.
Q 04Which element, with atomic number 1, is the lightest on the periodic table?
Hydrogen
Hydrogen, with atomic number 1, is the lightest and most abundant chemical element in the universe, consisting of a single proton and typically one electron.
Q 05What subatomic particle found in the nucleus of an atom carries a positive electric charge?
Proton
Protons are stable subatomic particles found in the nucleus of an atom, carrying a positive electric charge.
Q 06What is the chemical symbol for the element gold?
Au
Au is the chemical symbol for gold, derived from its Latin name, aurum. Ag is silver, Fe is iron, and Pb is lead.
Q 07What is the common name for sodium chloride?
Table salt
Sodium chloride (NaCl) is commonly known as table salt. Baking soda is sodium bicarbonate, table sugar is sucrose, and Epsom salt is magnesium sulfate.
Q 08Which element has an atomic number of 8?
Oxygen
Oxygen has an atomic number of 8, meaning each atom of oxygen has 8 protons in its nucleus. Nitrogen is 7, Fluorine is 9, and Carbon is 6.
Q 09What is the approximate pH of pure water at 25°C?
7
Pure water at 25 °C has a pH of 7: H⁺ and OH⁻ are both 10⁻⁷ mol/L, so it is neutral. Heated above 25 °C, the neutral point drifts below 7.
Q 10What type of chemical bond has atoms sharing electron pairs, the kind that holds a water molecule together?
Covalent bond
A Covalent bond shares electrons; an ionic bond transfers them, a metallic bond pools them, and a hydrogen bond is just an attraction between molecules, the one that makes ice float.
Q 11Which functional group has a carbon double-bonded to oxygen and bonded to a hydrogen and an R group?
Aldehyde
An aldehyde group (R–CHO) has its carbonyl carbon bonded to one hydrogen and one alkyl or aryl group; formaldehyde (HCHO) and acetaldehyde (CH₃CHO) are the simplest examples.
Q 12In a redox reaction, what term describes the loss of electrons by a chemical species?
Oxidation
Oxidation is defined as the loss of electrons, or an increase in oxidation state. Reduction is the gain of electrons.
Q 13Which reaction type has an acid and a base forming a salt and water?
Neutralization
Neutralization is the reaction of an acid with a base to give a salt and water; hydrochloric acid and sodium hydroxide yield sodium chloride and water (HCl + NaOH → NaCl + H₂O).
Q 21A solution with a pH of 2 is considered what type of substance?
Acidic
The pH scale ranges from 0 to 14, where values below 7 indicate acidity, values above 7 indicate alkalinity (basicity), and 7 is neutral.
Q 22Who is credited with the discovery of the electron?
J.J. Thomson
His 1897 cathode-ray experiments showed the particles were far smaller than atoms; the electron was the first subatomic particle ever discovered, and Thomson won the 1906 Nobel Prize in Physics.
Q 23What is the primary chemical compound found in rust?
Iron oxide
Rust is primarily hydrated iron(III) oxide, which forms when iron and oxygen react in the presence of water or air moisture.
Q 14What is the typical oxidation number of an uncombined element?
0
An element in its free, uncombined form (e.g., O2, Fe, H2) has an oxidation number of 0.
Q 15Which characteristic is commonly associated with transition metals?
Formation of colored compounds
Transition metals are known for their ability to form compounds in multiple oxidation states and frequently produce brightly colored compounds due to d-d electronic transitions. They generally have high melting points and are good electrical conductors.
Q 16Which functional group contains a carbonyl group bonded to two other carbon atoms?
Ketone
A ketone has its carbonyl (C=O) carbon bonded to two other carbon atoms, so the group sits inside the chain; acetone, CH₃COCH₃, is the simplest ketone.
Q 17An organic compound whose molecule carries a –COOH group belongs to which class?
Carboxylic acid
A carboxylic acid is defined by the –COOH group; acetic acid in vinegar and citric acid in lemons are everyday examples, and the carbonyl stabilises the anion left when the –OH proton leaves.
Q 18Which functional group, formed from a carboxylic acid and an alcohol, has an R-COO-R' structure?
Ester
An ester has the R–COO–R′ structure and forms by esterification, the condensation of a carboxylic acid with an alcohol; ethyl acetate, from acetic acid and ethanol, is a familiar example.
Q 19What is the smallest unit of an element that retains the chemical properties of that element?
Atom
Atoms are the fundamental building blocks of all matter and are defined by their number of protons. They are the smallest units that maintain an element's distinct chemical identity.
Q 20Which gas makes up about 78% of Earth's atmosphere by volume?
Nitrogen
Nitrogen (N₂) makes up about 78% of dry air by volume; oxygen is about 21%, argon just under 1%, and carbon dioxide roughly 0.04%.
Q 24Which group of elements, with full outer electron shells, sits in the table's last column and barely reacts with anything?
Noble Gases
Noble Gases were left off Mendeleev's first table entirely, since none had been discovered; he added them as 'group 0' in 1902 once helium and argon were accepted.
Q 25Which branch of chemistry primarily studies compounds containing carbon-hydrogen bonds?
Organic Chemistry
Organic chemistry is dedicated to the study of the structure, properties, composition, reactions, and preparation of carbon-containing compounds.
Q 26What is it called when a solid changes directly into a gas without becoming liquid?
Sublimation
Sublimation is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point.
Q 27Atoms of the same element with different numbers of neutrons, such as carbon-12 and carbon-14, are called what?
Isotopes
Isotopes share a proton count and a place in the table, which is what the name means, 'same place'; ions differ in electrons, allotropes in structure.
Q 28What term describes a substance that speeds up a chemical reaction without being consumed?
Catalyst
A catalyst speeds up a reaction without being consumed, opening a lower-energy pathway; the platinum in a car's catalytic converter is a familiar example.
Q 29What type of chemical reaction releases energy, often as heat or light?
Exothermic
Exothermic reactions have a negative enthalpy change (ΔH < 0), indicating that the products have lower energy than the reactants and the excess energy is released.
Q 30What type of hybridization does the carbon atom exhibit in a methane (CH₄) molecule?
sp³
In methane, the carbon atom undergoes sp³ hybridization, where one 2s and three 2p atomic orbitals combine to form four equivalent sp³ hybrid orbitals, resulting in a tetrahedral geometry.