Multiple Choice
Bromine has two naturally occurring isotopes, Br-79 and Br-81, with an atomic mass of 79.904 amu. Given that the mass of Br-81 is 80.9163 amu and its natural abundance is 49.31%, what is the mass and natural abundance of Br-79?
2. Atoms & Elements
Isotopes
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A sample of chlorine weighing 20.57 grams contains two naturally occurring isotopes: Cl-35 and Cl-37. If the atomic masses are 34.9689 amu for Cl-35 and 36.9659 amu for Cl-37, and the natural abundance of Cl-35 is approximately 75.78%, what is the mass of Cl-35 in the sample?
A
4.98 grams
B
15.59 grams
C
10.29 grams
D
5.98 grams
Verified step by step guidance1
Start by understanding that the sample of chlorine consists of two isotopes: Cl-35 and Cl-37. The problem provides the atomic masses and the natural abundance of Cl-35.
Calculate the mass of Cl-35 in the sample using its natural abundance. The natural abundance of Cl-35 is given as 75.78%, which means 75.78% of the total mass of the chlorine sample is Cl-35.
Convert the percentage of Cl-35 to a decimal by dividing by 100. This gives you 0.7578.
Multiply the total mass of the chlorine sample (20.57 grams) by the decimal form of the natural abundance of Cl-35 (0.7578) to find the mass of Cl-35 in the sample.
The equation for this calculation is: . Perform this multiplication to determine the mass of Cl-35 in the sample.
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