Ch.2 - Atoms & ElementsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: Pretend that a new element with an atomic weight of 342.38 amu was recently discovered. This element has two isotopes, the lighter of which has a mass of 340.91 amu and an abundance of 68.322%. What i

Problem

Pretend that a new element with an atomic weight of 342.38 amu was recently discovered. This element has two isotopes, the lighter of which has a mass of 340.91 amu and an abundance of 68.322%. What is the mass of the heavier isotope?

 A) 348.67 

B) 343.29 

C) 345.55 

D) 342.38 

E) 350.21

Solution

We’re being asked to calculate the mass of a heavier isotope of an element. We can use the following equation:


Atomic Mass = mass×f.a.isotope 1 + mass×f.a.isotope 2 


Where:

atomic mass = average atomic mass of the element 

f.a. = fractional abundance of the isotope


To get f.a., we simply need to divide the given percent abundance by 100.


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