Question

Enriched weapons-grade uranium consists of 80% uranium-235 (235.044 amu) and 20% uranium-238 (238.051 amu). what is the average atomic mass of weapons-grade uranium, assuming the percentages are exact?

Answer 1

To find the average atomic mass of weapons-grade uranium, calculate the weighted average based on the percentages of each isotope: 80% of 235.044 amu (uranium-235) and 20% of 238.051 amu (uranium-238), yielding an average atomic mass of 235.6454 amu.

Step-by-step explanation:

To calculate the average atomic mass of weapons-grade uranium, which consists of 80% uranium-235 and 20% uranium-238, you multiply the mass of each isotope by its relative percentage (expressed as a decimal) and then sum the results. The atomic mass unit (amu) for uranium-235 is 235.044 and for uranium-238 is 238.051.

The average atomic mass can be calculated as follows:

(80% of uranium-235) 80/100 × 235.044 amu = 188.0352 amu

(20% of uranium-238) 20/100 × 238.051 amu = 47.6102 amu

Add these values together: 188.0352 amu + 47.6102 amu = 235.6454 amu

Therefore, the average atomic mass of weapons-grade uranium is 235.6454 amu.

Answer 2

isotopes are atoms of the same element that have the same number of protons with different numbers of neutrons, hence they have different masses.
the natural abundance of these elements vary, we are given percentages in which these isotopes exist.
average atomic mass is the weighted average atomic mass of an atom relative to 1/12th the mass of a C-12 atom. the average atomic mass can be calculated by taking the sum of the masses of isotopes multiplied by the respective abundance percentage
average atomic mass = (235.044 amu x 80%) + (238.051 amu x 20%)
= 188.04 + 47.61
= 235.65 amu
the average atomic mass is 235.65 amu