Atomic and Molecular Masses — Prelims Questions

An element X has two isotopes: $^{63}X$ with an atomic mass of 62.9296 u and a natural abundance of 69.17%, and $^{65}X$ with an atomic mass of 64.9278 u and a natural abundance of 30.83%. Calculate the average atomic mass of element X.

What is the molecular mass of urea, $CO(NH_2)_2$? (Given atomic masses: C = 12.01 u, O = 16.00 u, N = 14.01 u, H = 1.01 u)

Which of the following statements about atomic mass unit (amu) is correct?

The average atomic mass of Boron (B) is 10.81 u. Boron has two isotopes: $^{10}B$ with an atomic mass of 10.01 u and $^{11}B$ with an atomic mass of 11.01 u. What is the approximate percentage abundance of the $^{10}B$ isotope?

Which of the following compounds requires the use of 'formula mass' instead of 'molecular mass' for its quantitative description?

If the atomic mass of an element is 32.06 u, what is its molar mass?