Answer:
74.1 amu
Step-by-step explanation:
Given that,
The molecular mass of propanoic acid is 74.1 amu.
One of the isomer of propanoic acid is methyl ethanoate.
We know that, isomers are have same molecular formula. They also have same mass.
In this case, it is very clear that the molecular mass of methyl ethanoate is as same as molecular mass of propanoic acid i.e. 74.1 amu