Question

The average mass of a carbon atom is 12.011. Assuming you were able to pick up only one carbon atom, the chance that you would randomly get one with a mass of 12.011 is a. 0%. b. 0.011%. c. about 12%. d. 12.011%. e. greater than 50%. f. None of these is true. Explain.

Answer 1

Answer: Option (a) is the correct answer.

Explanation:

Average atomic mass of an element is defined as the sum of masses of its isotopes and each of them is multiplied by its natural abundance.

For example, in $^{12}C$ there is 99% $^{12}C$ and 1%$^{13}C$ is present. Hence, its mass will be calculated as follows.

          = $(12 \times 0.99) + (13 \times 0.01)$

          = 11.88 + 0.13

          = 12.01

This means one atom of carbon will not contribute to its mass as 12.011 but isotopes of carbon will attribute to it.

Thus, we can conclude that assuming you were able to pick up only one carbon atom, the chance that you would randomly get one with a mass of 12.011 is 0%.

Answer 2

The answer is A. Now, That answer above is terrific, but I’ll try and simplify it a little. Because the question is speaking of Carbon’s average mass, it is talking about what one carbon atom is predicted to weigh if you take into account all it’s possible isotopes (An isotope is just a form of an atom with differing numbers of neutrons in its nucleus.) Because an element can only have a whole number isotope (you can’t have an atom with 12.011 neutrons, only 12, 13, 14...) the answer must be a