In a mass spectrometer, a sample of neon exhibits two major isotopic peaks: ²⁰Ne (abundance 90.5%) and ²²Ne (abundance 9.5%). What is the relative atomic mass of neon?
Answer and explanation
Correct answer: D. 20.19
- Step 1: Calculate weighted average mass: .
- Step 2: Compute: .
Answer
20.19.
Why not the others: 21.00 is a simple unweighted arithmetic mean; 20.50 assumes equal 50% abundances; 21.81 inverts the isotope proportions.
Practise more Matter, Atomic Structure and Chemical Bonding.
Free questions with an explanation for every one, and full timed EmSAT Achieve (UAE) mock tests.
More Matter, Atomic Structure and Chemical Bonding questions
- What is the complete ground-state electron configuration of a neutral iron atom (atomic number Z = 26)?
- Which of the following elements has the highest first ionization energy?
- According to VSEPR theory, what is the molecular geometry of sulfur tetrafluoride (SF₄)?
- What mass of anhydrous sodium carbonate (Na₂CO₃, molar mass = 106 g/mol) is required to prepare 250 mL of a 0.20 M aqueous solution?
- Which intermolecular force is primarily responsible for the unusually high boiling point of water compared to hydrogen sulfide (H₂S)?
- A compound consists of 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. What is its empirical formula? (Atomic masses: C = 12.0, H = 1…