(2.8)An element occurs as three isotopes with atomic masses 19.99 amu (abundance = 90.51%), 20.99 amu (abundance = 0.27%), and 21.99 amu (abundance 9.22%). What is the atomic mass of the element? 62.97 amu 20.18 amu 21.00 amu 21.01 amu

Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
icon
Related questions
Question
### Problem Statement

An element occurs as three isotopes with atomic masses 19.99 amu (abundance = 90.51%), 20.99 amu (abundance = 0.27%), and 21.99 amu (abundance = 9.22%). What is the atomic mass of the element?

- [ ] 62.97 amu
- [ ] 20.18 amu
- [ ] 21.00 amu
- [ ] 21.01 amu

### Explanation

To determine the atomic mass of the element with given isotopes, we use the concept of the weighted average of the isotopic masses. The formula for calculating the atomic mass (\(M\)) is:

\[ M = (m_1 \times f_1) + (m_2 \times f_2) + (m_3 \times f_3) \]

where \(m_1, m_2, m_3\) are the atomic masses of the isotopes and \(f_1, f_2, f_3\) are their respective fractional abundances.

**Step-by-Step Calculation:**

1. Convert the percentage abundances into fractional abundances:
   - Isotope 1: 90.51% = 0.9051
   - Isotope 2: 0.27% = 0.0027
   - Isotope 3: 9.22% = 0.0922

2. Perform the weighted average calculation:
   \[ M = (19.99 \times 0.9051) + (20.99 \times 0.0027) + (21.99 \times 0.0922) \]

3. Resolve each term of the sum:
   - \(19.99 \times 0.9051 = 18.0954\)
   - \(20.99 \times 0.0027 = 0.0567\)
   - \(21.99 \times 0.0922 = 2.0294\)

4. Summing these values gives the atomic mass:
   \[ M = 18.0954 + 0.0567 + 2.0294 = 20.1815 \]

Therefore, the atomic mass of the element is approximately **20.18 amu** which matches one of the options
Transcribed Image Text:### Problem Statement An element occurs as three isotopes with atomic masses 19.99 amu (abundance = 90.51%), 20.99 amu (abundance = 0.27%), and 21.99 amu (abundance = 9.22%). What is the atomic mass of the element? - [ ] 62.97 amu - [ ] 20.18 amu - [ ] 21.00 amu - [ ] 21.01 amu ### Explanation To determine the atomic mass of the element with given isotopes, we use the concept of the weighted average of the isotopic masses. The formula for calculating the atomic mass (\(M\)) is: \[ M = (m_1 \times f_1) + (m_2 \times f_2) + (m_3 \times f_3) \] where \(m_1, m_2, m_3\) are the atomic masses of the isotopes and \(f_1, f_2, f_3\) are their respective fractional abundances. **Step-by-Step Calculation:** 1. Convert the percentage abundances into fractional abundances: - Isotope 1: 90.51% = 0.9051 - Isotope 2: 0.27% = 0.0027 - Isotope 3: 9.22% = 0.0922 2. Perform the weighted average calculation: \[ M = (19.99 \times 0.9051) + (20.99 \times 0.0027) + (21.99 \times 0.0922) \] 3. Resolve each term of the sum: - \(19.99 \times 0.9051 = 18.0954\) - \(20.99 \times 0.0027 = 0.0567\) - \(21.99 \times 0.0922 = 2.0294\) 4. Summing these values gives the atomic mass: \[ M = 18.0954 + 0.0567 + 2.0294 = 20.1815 \] Therefore, the atomic mass of the element is approximately **20.18 amu** which matches one of the options
Expert Solution
trending now

Trending now

This is a popular solution!

steps

Step by step

Solved in 2 steps with 1 images

Blurred answer
Knowledge Booster
Atomic Structure and Spectra
Learn more about
Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, chemistry and related others by exploring similar questions and additional content below.
Recommended textbooks for you
Chemistry
Chemistry
Chemistry
ISBN:
9781305957404
Author:
Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:
Cengage Learning
Chemistry
Chemistry
Chemistry
ISBN:
9781259911156
Author:
Raymond Chang Dr., Jason Overby Professor
Publisher:
McGraw-Hill Education
Principles of Instrumental Analysis
Principles of Instrumental Analysis
Chemistry
ISBN:
9781305577213
Author:
Douglas A. Skoog, F. James Holler, Stanley R. Crouch
Publisher:
Cengage Learning
Organic Chemistry
Organic Chemistry
Chemistry
ISBN:
9780078021558
Author:
Janice Gorzynski Smith Dr.
Publisher:
McGraw-Hill Education
Chemistry: Principles and Reactions
Chemistry: Principles and Reactions
Chemistry
ISBN:
9781305079373
Author:
William L. Masterton, Cecile N. Hurley
Publisher:
Cengage Learning
Elementary Principles of Chemical Processes, Bind…
Elementary Principles of Chemical Processes, Bind…
Chemistry
ISBN:
9781118431221
Author:
Richard M. Felder, Ronald W. Rousseau, Lisa G. Bullard
Publisher:
WILEY