Multiple Choice
Antimony has two naturally occurring isotopes: Sb-121 with a mass of 120.904 amu and a natural abundance of 57.21%, and Sb-123. If the atomic mass of antimony is 121.760 amu, what is the mass of Sb-123?
2. Atoms & Elements
Isotopes
Struggling with General Chemistry?
Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
Gallium has two naturally occurring isotopes: Ga-69 with a mass of 68.9256 amu and a natural abundance of 60.11%, and Ga-71. If the atomic mass of gallium is 69.723 amu, what is the mass of Ga-71?
A
70.9247 amu
B
69.723 amu
C
68.9256 amu
D
71.926 amu
Verified step by step guidance1
Understand that the atomic mass of an element is the weighted average of the masses of its isotopes, based on their natural abundances.
Set up the equation for the average atomic mass of gallium using the formula: \( \text{Atomic Mass} = (\text{Mass of Ga-69} \times \text{Abundance of Ga-69}) + (\text{Mass of Ga-71} \times \text{Abundance of Ga-71}) \).
Substitute the known values into the equation: \( 69.723 = (68.9256 \times 0.6011) + (\text{Mass of Ga-71} \times (1 - 0.6011)) \).
Solve for the mass of Ga-71 by isolating it on one side of the equation. First, calculate the contribution of Ga-69 to the atomic mass, then rearrange the equation to solve for the mass of Ga-71.
Perform the necessary arithmetic operations to find the mass of Ga-71, ensuring that all calculations are done with appropriate significant figures.
Related Videos
Related Practice
