7.1 Relative atomic mass and relative formula mass

Which element is used as a standard to determine the relative mass of atoms and molecules?

• Oxygen

• Hydrogen

• Nitrogen

• Carbon

The relative atomic mass of an element is the average mass of _____ of that element relative to ___ the mass of a carbon-12 atom.

• a molecule; 1

• an atom; 1/12

• an atom; 1

• a molecule; 1/12

Relative molecular mass is the average mass of _____ of that substance relative to ___ the mass of a carbon-12 atom.

• a molecule; 1

• an atom; 1/12

• an atom; 1

• a molecule; 1/12

The method to calculate relative molecular mass is the same as the method to calculate relative formula mass.

• True

• False

Relative molecular mass is the exact same thing as relative formula mass.

• True

• False

The unit for relative atomic/molecular/formula mass is _____.

• g

• A_r

• M_r

• No unit

Oxygen has a A_r of 16. Which statement is true?

• An oxygen atom is 16g.

• An oxygen molecule is 16g.

• An oxygen atom is 16X the mass of 1/12 of a carbon-12 atom.

• An oxygen molecule is 16X the mass of 1/12 of a carbon-12 atom.

How do we find the A_r of an element?

How do we find the M_r of a molecule/compound?

Find the M_r of C₂H₅COOH.