Free Moles and Avogadro's Number MCQs with Answers
117 Moles and Avogadro's Number MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
The mole connects the microscopic number of particles with measurable mass, using Avogadro's number, 6.022 × 10²³ particles per mole. Questions involve molar mass, conversion between mass, moles and particles, percentage composition, empirical and molecular formulas, and distinguishing atoms, molecules, ions and formula units.
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- A. 1.008 mg
- B. 0.184 mg
- C. 0.054 mg
- D. 5.4 mg
Explanation: The mass of one electron is about 9.11 x 10^-31 kg, so the mass of 0.1 mol of electrons is 0.1 x 6.022 x 10^23 x 9.11 x 10^-31 kg = 5.49 x…
Correct answer: 0.054 mg- A. relative atomic mass
- B. mass number
- C. atomic weight
- D. relative isotopic mass
Explanation: The value 35.5 is the weighted average relative atomic mass of naturally occurring chlorine isotopes, mainly 35Cl and 37Cl.
Correct answer: relative atomic mass- A. 1.6 x 10^-27 kg
- B. 1.6 x 10^-24 kg
- C. 1.6 x 10^-26 kg
- D. 1.6 x 10^-28 kg
Explanation: One atomic mass unit is defined as approximately 1.66 x 10^-27 kg, which is rounded in the options to 1.6 x 10^-27 kg.
Correct answer: 1.6 x 10^-27 kg44. The properties of an element mosly corresponds to that isotope which has greater_________________?
- A. Mass number
- B. Atomic mass
- C. Relative abundance
- D. all of the above
Explanation: An element's observed atomic properties usually reflect the isotope that occurs in the greatest relative abundance, because that isotope…
Correct answer: Relative abundance- A. NaCl
- B. H2O
- C. CCI4
- D. It can be applied to all mentioned above
Explanation: An empirical formula gives the simplest whole-number ratio of atoms. NaCl is already in its simplest ratio, H2O cannot be reduced, and…
Correct answer: It can be applied to all mentioned above- A. lighter
- B. intermediate
- C. heavier
- D. are collected at same time
Explanation: In a magnetic field, charged particles with lower mass-to-charge ratio are deflected more strongly, so lighter cationic molecular ions…
Correct answer: lighter- A. different number of protons
- B. same number of neutrons
- C. different number of neutrons
- D. same mass number (nucleon number)
Explanation: Isotopes are atoms of the same element, so they have the same number of protons but different numbers of neutrons.
Correct answer: different number of neutrons- A. Mass of an atom itself is in fraction
- B. Atomic masses are average masses of isobars
- C. Atmoic masses are average masses of isotopes proportional to their relative abundance
- D. Atmoic masses are average masses of isotopes
Explanation: The atomic mass of an element is a weighted average of the masses of its naturally occurring isotopes, with each isotope weighted…
Correct answer: Atmoic masses are average masses of isotopes proportional to their relative abundance- A. 80%
- B. 30%
- C. 40%
- D. 20%
Explanation: Using CaCO3 = 40 + 12 + (3 x 16) = 100 g mol^-1, the calcium percentage is (40 g mol^-1 / 100 g mol^-1) x 100 = 40%.
Correct answer: 40%- A. 0.25
- B. 0.5
- C. 0.75
- D. 1
Explanation: One mole of CO2 contains two moles of oxygen atoms, equal to 2 x 16 g = 32 g of oxygen.
Correct answer: 0.5- A. oxygen
- B. carbon
- C. tin
- D. chlorine
Explanation: Tin has the greatest number of naturally occurring stable isotopes among the listed elements, with ten commonly recognized stable…
Correct answer: tin- A. 280
- B. 300
- C. 154
- D. 54
Explanation: For isotopes with even atomic number and even mass number, both the proton number and neutron number are even, a combination that gives…
Correct answer: 154- A. Isotopes with odd atomic number are abundant
- B. Isotopes with odd atomic number and even mass number are abundant
- C. Isotopes with even atomic number and even mass number are abundant
- D. Isotopes with even atomic number and odd mass no are abundant
Explanation: Nuclei with even atomic number and even mass number have both an even proton number and an even neutron number, so the nucleons can be…
Correct answer: Isotopes with even atomic number and even mass number are abundant- A. 1-mole molecules of water
- B. 1-gram molecule of water
- C. 3-gram atoms
- D. all
Explanation: The molar mass of water is 2 x 1 + 16 = 18 g mol^-1, so 18 g of water is 1 mol of H2O molecules and is also called 1 gram-molecule.
Correct answer: all- A. Anemic
- B. Cannot be determined
- C. Normal
- D. Polycythemic
Explanation: To determine whether Jimmy is anemic or not, we need to calculate his hemoglobin count based on the given red blood cell count.One red…
Correct answer: Anemic- A. 1.07 kg
- B. 48.9 g
- C. 0.897 g
- D. 0.489 kg
Explanation: Each student requires 10 g of NaOH, therefore, the total amount of NaOH required for 42 students is:10 g/student x 42 students = 420 gThe…
Correct answer: 0.489 kg- A. 0.0177
- B. 0.001
- C. 0.5
- D. 0.244
Explanation: Mole fraction of a component X in a solution is defined as the ratio of the number of moles of X to the total number of moles of all…
Correct answer: 0.0177- A. Y = 13%, Ba = 41%, Cu = 29%, O = 17%
- B. Y = 17%, Ba = 39%, Cu = 23%, O = 21%
- C. Y = 15%, Ba = 52%, Cu = 10%, O = 23%
- D. Y = 19%, Ba = 41%, Cu = 31%, O = 9%
Explanation: To find the mass percentage of each element in YBa₂Cu₃O₇, we need to first calculate its molar mass, which is:1(Y) + 2(Ba) + 3(Cu) + 7(O)…
Correct answer: Y = 13%, Ba = 41%, Cu = 29%, O = 17%- A. 2.408x10%
- B. 24.08x10%
- C. 1.204 x 10^24
- D. 6.02x10
Explanation: As 1 molecule of water (18g) need 1 molecule of H2 then 2 molecule of water (36g) need 2 molecule of H2 which is 1.204 * 1024
Correct answer: 1.204 x 10^2460. If N is the number of molecules of a gas in a container. The number of moles can be calculated as:
- A. AN+NA
- B. NA/N
- C. N/NA
- D. N*NA
Explanation: We know that the number of molecules= no. of moles * Avogadro's numberN= no. of moles * NAAdjusting the equationNo. of moles = N/NA.
Correct answer: N/NA