Table of contents

1. Intro to General Chemistry3h 48m
2. Atoms & Elements4h 16m
3. Chemical Reactions4h 10m
4. BONUS: Lab Techniques and Procedures1h 38m
5. BONUS: Mathematical Operations and Functions48m
6. Chemical Quantities & Aqueous Reactions3h 53m
7. Gases3h 49m
8. Thermochemistry2h 37m
9. Quantum Mechanics2h 58m
10. Periodic Properties of the Elements3h 9m
11. Bonding & Molecular Structure3h 29m
12. Molecular Shapes & Valence Bond Theory1h 57m
13. Liquids, Solids & Intermolecular Forces2h 23m
14. Solutions3h 1m
15. Chemical Kinetics2h 53m
16. Chemical Equilibrium2h 29m
17. Acid and Base Equilibrium5h 1m
18. Aqueous Equilibrium4h 47m
19. Chemical Thermodynamics1h 50m
20. Electrochemistry2h 42m
21. Nuclear Chemistry2h 36m
22. Organic Chemistry5h 7m
23. Chemistry of the Nonmetals2h 39m
24. Transition Metals and Coordination Compounds3h 16m

2. Atoms & Elements

Atomic Mass

General Chemistry

2. Atoms & Elements

Atomic Mass

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Multiple Choice

An element has two naturally occurring isotopes. One has an abundance of 37.40% and an isotopic mass of 184.953 amu, and the other has an abundance of 62.60% and a mass of 186.956 amu. What is the average atomic mass of the element?

186.500 amu

185.000 amu

186.000 amu

185.847 amu

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Verified step by step guidance

Identify the isotopic abundances and masses: Isotope 1 has an abundance of 37.40% and a mass of 184.953 amu, while Isotope 2 has an abundance of 62.60% and a mass of 186.956 amu.

Convert the percentage abundances into decimal form by dividing by 100: 37.40% becomes 0.3740 and 62.60% becomes 0.6260.

Calculate the contribution of each isotope to the average atomic mass by multiplying the isotopic mass by its decimal abundance: For Isotope 1, multiply 184.953 amu by 0.3740. For Isotope 2, multiply 186.956 amu by 0.6260.

Add the contributions from both isotopes to find the average atomic mass of the element: Sum the results from the previous step.

The calculated average atomic mass will be the weighted average based on the isotopic abundances and masses, which should match one of the given options.