All Free Chemistry MCQs with Answers
Every Chemistry question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
13,720 questions · page 1 of 686
- A. Neutrons in the nucleus
- B. Protons in the nucleus
- C. Protons and neutrons combined
- D. Electron shells
Explanation: The atomic number equals the number of protons in the nucleus and determines the identity of the element.
Correct answer: Protons in the nucleus- A. Covalent bond
- B. Ionic bond
- C. Metallic bond
- D. Hydrogen bond
Explanation: Sodium transfers its single valence electron to chlorine, producing Na⁺ and Cl⁻ ions held together by electrostatic attraction — an ionic…
Correct answer: Ionic bond- A. shape of orbital
- B. main energy level and distance from the nucleus
- C. orientation of the orbital in space
- D. direction of spin
Explanation: The principal quantum number sets the shell, and therefore the main energy level and the average distance of the electron from the…
Correct answer: main energy level and distance from the nucleus- A. Three
- B. Five
- C. Seven
- D. Nine
Explanation: For the d subshell l equals 2, so m runs from minus 2 to plus 2, giving five values and therefore five orbitals.
Correct answer: Five- A. n = 2, l = 1, m = 0
- B. n = 3, l = 2, m = -2
- C. n = 2, l = 2, m = 1
- D. n = 4, l = 0, m = 0
Explanation: The azimuthal quantum number l is restricted to values from 0 up to n minus 1, so with n equal to 2 the only allowed values of l are 0 and…
Correct answer: n = 2, l = 2, m = 1- A. 8
- B. 10
- C. 18
- D. 32
Explanation: The capacity of a shell is 2n squared, so for n equal to 3 that is 2 times 9, which is 18.
Correct answer: 18- A. spherical
- B. dumbbell shaped
- C. doughnut shaped
- D. tetrahedral
Explanation: A p orbital has two lobes on opposite sides of the nucleus with a node at the nucleus itself, giving the familiar dumbbell shape, and the…
Correct answer: dumbbell shaped- A. pair up in the first orbital before entering the next
- B. occupy separate orbitals with parallel spins before pairing
- C. occupy the orbital of highest energy first
- D. always pair with opposite spins immediately
Explanation: Electrons repel one another, so they spread across orbitals of equal energy singly and with parallel spins before any orbital takes a…
Correct answer: occupy separate orbitals with parallel spins before pairing- A. [Ar] 3d4 4s2
- B. [Ar] 3d5 4s1
- C. [Ar] 3d6 4s0
- D. [Ar] 3d3 4s3
Explanation: Chromium promotes one 4s electron into the 3d subshell because a half filled d5 configuration alongside a half filled 4s is more stable…
Correct answer: [Ar] 3d5 4s1- A. continuously in any amount
- B. in discrete packets whose energy is proportional to frequency
- C. only as heat
- D. in packets whose energy is proportional to wavelength
Explanation: Planck proposed that radiation is emitted in quanta of energy E equal to h times the frequency, where h is Planck's constant.
Correct answer: in discrete packets whose energy is proportional to frequency- A. n = 1
- B. n = 2
- C. n = 3
- D. n = 4
Explanation: The Balmer series arises from transitions ending at n equal to 2 and it is the only hydrogen series that falls in the visible region…
Correct answer: n = 2- A. electrons can have any energy value
- B. electron energies inside an atom are quantised
- C. the nucleus contains neutrons
- D. hydrogen atoms contain more than one electron
Explanation: A hot gas emits light only at particular wavelengths, producing separate bright lines instead of a continuous band, and each line…
Correct answer: electron energies inside an atom are quantised- A. the cathode of the discharge tube
- B. the residual gas atoms losing electrons in a discharge tube
- C. the radioactive decay of uranium
- D. the anode metal evaporating
Explanation: Goldstein observed that cathode rays travelling through a perforated cathode knocked electrons off the residual gas atoms, leaving…
Correct answer: the residual gas atoms losing electrons in a discharge tube- A. 4p
- B. 3d
- C. 4d
- D. 5s
Explanation: Orbitals fill in order of increasing n plus l, and where that sum ties the lower n goes first.
Correct answer: 3d- A. directly proportional to its pressure
- B. inversely proportional to its pressure
- C. independent of its pressure
- D. proportional to the square of its pressure
Explanation: Boyle's law gives PV equal to a constant, so doubling the pressure halves the volume.
Correct answer: inversely proportional to its pressure- A. 200 cm3
- B. 250 cm3
- C. 1250 cm3
- D. 100 cm3
Explanation: Applying P1V1 equal to P2V2 gives V2 equal to 2 times 500 divided by 5, which is 200 cm3.
Correct answer: 200 cm3- A. 25 degrees C and 1 atm
- B. 0 degrees C and 1 atm
- C. 0 K and 1 atm
- D. 25 degrees C and 760 mm of mercury above atmospheric
Explanation: STP is 273.15 K, which is 0 degrees Celsius, at a pressure of 1 atmosphere or 760 mm of mercury.
Correct answer: 0 degrees C and 1 atm- A. 0 degrees C
- B. -100 degrees C
- C. -273.15 degrees C
- D. -373 degrees C
Explanation: Extrapolating the straight line of volume against temperature backwards, every gas reaches zero volume at minus 273.15 degrees Celsius…
Correct answer: -273.15 degrees C- A. 54 degrees C
- B. 300 degrees C
- C. 327 degrees C
- D. 600 degrees C
Explanation: Charles's law must be applied in kelvin, so the initial temperature is 27 plus 273, which is 300 K.
Correct answer: 327 degrees C- A. Gas molecules attract one another strongly
- B. The volume of the molecules themselves is negligible compared with the volume of the container
- C. Collisions between molecules lose energy as heat
- D. The molecules all move at the same speed
Explanation: The ideal model treats molecules as point masses with negligible volume and no intermolecular forces, colliding perfectly elastically so…
Correct answer: The volume of the molecules themselves is negligible compared with the volume of the container