A certain element XX has four isotopes. 5.845% of XX has a mass of 53.93961 amuamu. 91.75% of XX has a mass of 55.93494 amuamu. 2.123% of XX has a mass of 56.93539 amuamu. 0.2820% of XX has a mass of 57.93328 amuamu. What is the average atomic mass of element XX? Express your answer numerically to four signif

55.85 amu

Explanation:

Let A, B, C and D represent the four isotopes of element X.

The following data were obtained from the question:

Isotope A:

Abundance (A%) = 5.845%

Mass of A = 53.93961 amu

Isotope B:

Abundance (B%) = 91.75%

Mass of B = 55.93494 amu

Isotope C:

Abundance (C%) = 2.123%

Mass of C = 56.93539 amu

Isotope D:

Abundance (D%) = 0.2820%

Mass of D = 57.93328 amu

Average atomic mass of element X =.?

The average atomic mass of X can be obtained as follow:

Average Atomic mass = [(Mass of A × A%)/100] + [(Mass of B × B%)/100] + [(Mass of C × C%)/100] + [(Mass of D × D%)/100]

Average Atomic mass = [(53.93961 × 5.845)/100] + [(55.93494 × 91.75)/100] + [(56.93539 × 2.123)/100] + [(57.93328 × 0.2820)/100]

= 3.15277 + 51.32031 + 1.20874 + 0.16337

= 55.84519 ≈ 55.85

Therefore, the average atomic mass of X is 55.85 amu

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