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What is the first step in calculating the atomic mass of an element with two isotopes?
What is the first step in calculating the atomic mass of an element with two isotopes?
- Determine the atomic mass of each isotope.
- Convert the atomic masses to decimals.
- Find the percentage abundance of each isotope. (correct)
- Calculate the average of the atomic masses.
How do you calculate the contribution of each isotope to the atomic mass?
How do you calculate the contribution of each isotope to the atomic mass?
- Multiply the atomic mass of the isotope by its percentage as a decimal. (correct)
- Add the atomic masses of both isotopes together.
- Subtract the smaller atomic mass from the larger one.
- Divide the atomic mass by the total number of isotopes.
In the calculation of chlorine's atomic mass, what is the contribution of the isotope with an atomic mass of 37.29 amu?
In the calculation of chlorine's atomic mass, what is the contribution of the isotope with an atomic mass of 37.29 amu?
- 35.91 amu
- 37.29 amu
- 9.323 amu (correct)
- 26.59 amu
What percentage must total 100% in an atomic mass calculation involving two isotopes?
What percentage must total 100% in an atomic mass calculation involving two isotopes?
If one isotope of indium has an atomic mass of 114.9041 amu and an abundance of 95.795%, what is the abundance of the second isotope?
If one isotope of indium has an atomic mass of 114.9041 amu and an abundance of 95.795%, what is the abundance of the second isotope?
What is the formula to calculate the atomic mass based on isotopes?
What is the formula to calculate the atomic mass based on isotopes?
Which statement correctly defines isotopes?
Which statement correctly defines isotopes?
The atomic mass unit (amu) is defined as what fraction of the mass of a Carbon-12 atom?
The atomic mass unit (amu) is defined as what fraction of the mass of a Carbon-12 atom?
Which factors are required to calculate the atomic mass of an element?
Which factors are required to calculate the atomic mass of an element?
What does the presence of decimal points in atomic masses indicate?
What does the presence of decimal points in atomic masses indicate?
In a weighted average calculation, how much percentage do tests contribute to the final grade in the given example?
In a weighted average calculation, how much percentage do tests contribute to the final grade in the given example?
If an element has two isotopes with masses of 10 amu and 12 amu and their natural abundances are 80% and 20% respectively, what is the approximate atomic mass of the element?
If an element has two isotopes with masses of 10 amu and 12 amu and their natural abundances are 80% and 20% respectively, what is the approximate atomic mass of the element?
What is the primary reason atomic mass values on the periodic table usually have decimal points?
What is the primary reason atomic mass values on the periodic table usually have decimal points?
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Study Notes
Atomic Mass Units (amu)
- The atomic mass of an element is measured in atomic mass units (amu)
- One atomic mass unit (amu) is defined as 1/12 the mass of a carbon-12 atom.
Calculating Atomic Mass
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Atomic mass is the weighted average of the masses of all the isotopes of an element.
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The atomic mass of an element can be calculated using the following formula:
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(Atomic mass 1 * %1/100) + (Atomic mass 2 * %2/100) + ...*
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Where:
- Atomic mass 1 and 2 are the masses of the isotopes
- %1 and %2 are the percent abundances of the isotopes
Example: Calculating the Atomic Mass of Chlorine
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There are two common isotopes of chlorine:
- Chlorine-35 with a mass of 35.45 amu and an abundance of 75.00%
- Chlorine-37 with a mass of 37.29 amu and an abundance of 25.00%
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To calculate the atomic mass of chlorine:
- (35.45 amu * 0.7500) + (37.29 amu * 0.2500) = 35.91 amu
Finding the Atomic Mass of an Isotope
- You can also use the atomic mass of the element and the percent abundance of one isotope to calculate the atomic mass of another isotope.
- Example: Indium has an atomic mass of 114.8200 amu. One isotope of indium has a mass of 114.9041 amu with an abundance of 95.795%. To find the atomic mass of the other isotope:
- Calculate the percent abundance of the second isotope: 100 - 95.795 = 4.205%
- Use the formula for calculating atomic mass: 114.8200 amu = (114.9041 amu * 0.95795) + (x * 0.04205)
- Solve for x: x = 113 amu
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