Question

The 18o:16o abundance ratio in some meteorites is greater than that used to calculate the average atomic mass of oxygen on earth. is the average mass of an oxygen atom in these meteorites greater than, less than, or equal to that of a terrestrial oxygen atom?

Answer 1

The terrestrial oxygen atom is the atom that has an atomic mass of 16. The atomic mass of the element is calculated through the equation,

               (x₁)(M₁) + (x₂)(M₂)

where x₁ and x₂ are the percentage abundance of each of the isotope of the element. M₁ and M₂ are the atomic masses. 

In this item, it is given that the value of x₁, say corresponding to percentage abundance of 18O. With this increase, the value of x₂ will decrease then, the value of the atomic mass of the element is GREATER than that of the terrestrial oxygen atom. 

Answer 2

Answer: The average mass of the oxygen atom in these meteorites will be greater than the terrestrial oxygen atom.

Explanation:

Average atomic mass of an element is defined as the summation of the product of the atomic masses and fractional abundances of its isotopes.

Equation to calculate the average atomic mass will be given by:

$\text{Average atomic mass}=\sum_{i=1}^n(\text{Atomic mass of an isotopes})_i\times (\text{fractional abundance})_i$

We are given that the abundance ratio of the oxygen in meteorites is more than the terrestrial oxygen atom.

As, from the formula, average atomic mass of an element is directly proportional to the fractional abundance of the isotopes. Hence, with increase in the abundance, the average atomic mass also increases.

Therefore, the average mass of the oxygen atom in these meteorites will be greater than the terrestrial oxygen atom.