NEET-UG and JEE Main Chemistry · Class 11
Atomic and molecular masses; average atomic mass — NEET & JEE Questions
Atomic and molecular masses; average atomic mass is a topic in Some Basic Concepts in Chemistry, a Class 11 Chemistry chapter of the NEET-UG and JEE Main syllabus. TestBudy holds 12 published NEET-UG and JEE Main questions on Atomic and molecular masses; average atomic mass, each with the marking scheme of the real paper.
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Atomic and molecular masses; average atomic mass MCQs with solutions
10 of the 12 published questions on this topic, exactly as they appear in a test. Answers and worked solutions come with your result rather than on this page.
One atomic mass unit, u, is defined as
- A. one-twelfth the mass of a carbon-12 atom
- B. the mass of one proton exactly
- C. the mass of one electron
- D. one gram
Relative atomic mass of an element is usually not an integer because
- A. it is a weighted average over naturally occurring isotopes
- B. every atom has fractional protons
- C. electrons have no mass
- D. isotopes have identical masses
The molecular mass of a molecule is obtained by
- A. adding the atomic masses of all atoms in its molecular formula
- B. multiplying all atomic masses together
- C. using only the heaviest atom
- D. counting only valence electrons
Average atomic mass is calculated using isotopic abundances as
- A. a weighted mean
- B. a simple sum without weighting
- C. the mass of the most abundant isotope only
- D. the arithmetic mean regardless of abundance
What is the molecular mass of using H = 1 and O = 16?
- A. 16 u
- B. 17 u
- C. 18 u
- D. 20 u
What is the molecular mass of using C = 12 and O = 16?
- A. 28 u
- B. 32 u
- C. 44 u
- D. 48 u
An element has two isotopes of masses 10 u and 11 u with abundances 20% and 80%, respectively. What is its average atomic mass?
- A. 10.2 u
- B. 10.5 u
- C. 10.8 u
- D. 11.0 u
An element has isotopes 35 u and 37 u in a 3:1 abundance ratio. What is the average atomic mass?
- A. 35.0 u
- B. 35.5 u
- C. 36.0 u
- D. 36.5 u
An element has average atomic mass 24.4 u and consists only of isotopes 24 u and 25 u. What fraction is isotope 25 u?
- A. 0.20
- B. 0.40
- C. 0.60
- D. 0.80
A molecule has formula . Using C = 12, H = 1 and O = 16, what is its molecular mass?
- A. 44 u
- B. 46 u
- C. 48 u
- D. 60 u
Common mistakes in Atomic and molecular masses; average atomic mass
Recorded against questions in this topic that are not shown above, so none of these points at an answer you can see on this page.
- Uses 0.6/65 instead of dividing the mass shift by the isotope mass difference of 2 u.
- Uses the arithmetic mean of the three isotope masses instead of abundance weighting.
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