High School

Given that Au-197 is the only natural isotope of gold, what is the mass of one Au atom and the mass of Avogadro's number of Au atoms, respectively?

A. 196.97 g and 196.97 amu
B. 197 amu and 197 g
C. 197 g and 197 amu
D. 196.97 amu and 196.97 g
E. None of the above

Answer :

Explanation:

The mass number of an element is a weighted average of all the isotopes of that element.

If Au has only one isotope then the atomic weight of that isotope matches the mass number.

Au-197 ==> mass number 197

Mass of one atom=mass number 197 amu

Mass of one mol of atoms:

[tex]m=197 amu*1.66054*10^{-24}g/amu*6.022*10^{23}[/tex]

[tex]m=196.97 g[/tex]

The mass of one Au atom is 196.97 amu from periodic table and the mass of Avogadro's number of Au atoms is 196.97 g due to this is the mass of one mole of gold