Here's how to calculate the mass of one molecule of carbon monoxide (CO):

1. Find the atomic masses:

* Carbon (C): 12.011 atomic mass units (amu)

* Oxygen (O): 15.9994 amu

2. Add the atomic masses together:

* 12.011 amu (C) + 15.9994 amu (O) = 28.0104 amu

Therefore, the mass of one molecule of carbon monoxide is approximately 28.0104 amu.