What is the average atomic mass of gold if half of the gold found in nature has a mass of 197 amu and half has a mass of 198 amu?

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Answer 1 · 2015-11-25T20:43:46

The average atomic mass is #197.5#.

Multiply the mass of each isotope times its percentage as a decimal number and add the results. #(50%)/100=0.5#

#"average atomic mass"=(0.5xx197)+(0.5xx198)=197.5#

Answer 2 · 2016-01-13T23:27:59

The average atomic mass is 198.5 u.

Assume that you have 2 atoms of gold.

Then you have 1 atom of each isotope.

#"Mass of 1 Au-197 atom = 197 u"#
#"Mass of 1 Au-198 atom = 198 u"#
#stackrel(———————————————)("Mass of 2 Au atoms"color(white)(Xl) = "395 u")#

#"Average mass" = "395 u"/2 = "197.5 u"#