Question

What is the formula mass of a compound with 2 aluminum atoms and 3 oxygen atoms?

Answer 1

Answer:

$\boxed {\boxed {\sf 101.96 \ amu}}$

Explanation:

Formula mass is the sum of the atomic masses of the atoms in a molecule. Essentially, it is the mass of 1 molecule of a compound.

We are given a compound containing 2 aluminum atoms and 3 oxygen atoms. We will use the Periodic Table to look up the atomic masses of the 2 elements in the compound.

• Al: 26.981538 amu
• O: 15.999 amu

These are the atomic masses of 1 atom of the element. Remember we have 2 Al atoms and 3 O atoms. We multiply the element's atomic mass by the number of atoms of that element in the compound.

• 2 Al: 26.981538 amu *2= 53.963076 amu
• 3 O: 15.999  amu * 3=47.997 amu

Now we add the atomic mass of 2 Al atoms and 3 O atoms.

• 53.963076 amu + 47.997 amu = 101.960076 amu

We may want to round this answer to the hundredth place. The 0 in the thousandth place tells us to leave the 6 in the hundredth place.

• 101.96 amu

The formula mass of a compound with 2 aluminum atoms and 3 oxygen atoms is approximately 101.96 atomic mass units.