# Problem: Prior to 1961, the atomic mass unit was defined as 1/16 the mass of the atomic mass of oxygen; that is, the atomic mass of oxygen was defined as exactly 16. The atomic mass of oxygen on todays scale is 15.9994. What was the mass in atomic mass units of a 40Ca atom prior to 1961 if its mass on todays scale is 39.9626?

###### FREE Expert Solution

We have to determine the mass of 40Ca in the atomic mass scale in use prior to 1961.

We have the following information:

Prior to 1961

16O = 16.0000 u

40Ca = ? amu

Current system

16O = 15.9994 u

40Ca = 39.9626 u

###### Problem Details

Prior to 1961, the atomic mass unit was defined as 1/16 the mass of the atomic mass of oxygen; that is, the atomic mass of oxygen was defined as exactly 16. The atomic mass of oxygen on todays scale is 15.9994. What was the mass in atomic mass units of a 40Ca atom prior to 1961 if its mass on todays scale is 39.9626?