In 1961, the reference for the atomic mass unit (amu or u) was changed from naturally occurring oxygen with a value of 16.000 u to one based on a single isotope of carbon (carbon-12). Why was it changed?
A. The atomic composition of oxygen varies depending upon its source.
B. Carbon-12 is more common than oxygen.
C. Carbon exists as only one isotope, carbon-12.
D. Carbon can combine with four atoms of hydrogen to form CH4, methane, while oxygen only combines with two atoms of hydrogen to form water, H2
Answer:A
In 1961, the reference for the atomic mass unit (amu or u) was changed from naturally occurring oxygen with a value of 16.000 u to one based on a single isotope of carbon (carbon-12). Why was it changed?
A. The atomic composition of oxygen varies depending upon its source. B. Carbon-12 is more common than oxygen. C. Carbon exists as only one isotope, carbon-12. D. Carbon can combine with four atoms of hydrogen to form CH4, methane, while oxygen only combines with two atoms of hydrogen to form water, H2