A generic element, Z, has two isotopes, 45Z and 47Z, and an average atomic mass of 45.36 amu. The natural abundances of the two isotopes are 80% 45Z and 20% 47Z. The isotopic mass of 45Z is 44.96 amu. What is the isotopic mass of 47Z?

46.96 amu

Explanation:

Isotopes are different kinds of same elements. The difference between two isotopes of the same element is the number of neutrons.

To get the relative atomic mass, we take into consideration the masses of the different isotopes. This is done by multiplying their abundances by their masses. They are then added together to get the relative atomic mass of the element.

Let the isotopic mass of 47Z be x

45.36 = [80/100 * 44.96] + [20/100 * x]

45.36 = 35.968 + 0.2x

0.2x = 45.36 - 35.968

0.2x = 9.392

x =9.392/0.2 = 46.96 amu

the answer is c. nacl