Calculating Relative Atomic Mass

Rubidium is a soft, silvery-white metal that has two common isotopes, 85-Rb and 87-Rb.

If the abundance of 85-Rb is 72.2% and the abundance of 87-Rb is 27.8%

What is the average atomic mass of rubidium?

(Do not include units)

(a)  

Uranium is used in nuclear reactors and is a rare element on earth.

Uranium has three

common isotopes. If the abundance of 234-U is 0.01%, the abundance of 235-U is 0.71%, and

the abundance of 238-U is 99.28%

What is the average atomic mass of uranium?

(Do not include units)

(a)  

Titanium has five common isotopes: 46Ti (8.0%), 47Ti (7.8%), 48Ti (73.4%),

49Ti (5.5%), 50Ti (5.3%).

What is the average atomic mass of titanium?

(Do not include units)

(a)  

Why is the mass in amu of a carbon-12 atom reported as 12.011 in the periodic table of the elements?

• It is based on an average of all its isotopes

• It is a mistake

• Because that is how it was discovered

• Because Carbon-12 is the standard for all atomic masses

Naturally occurring chlorine that is put in pools is 75.53 percent 35Cl (mass = 34.969 amu)

and 24.47 percent 37Cl (mass = 36.966 amu).

Calculate the average atomic mass.

(Do not include units)

(a)  

Iridium has a relative atomic mass of 192.22 and consists of Ir-191 and Ir-193 isotopes.

Calculate the percentage abundance of the isotope iridium- 191.

(a)