3.8 Formula Mass and the Mole Concept for Compounds

Question 1

we defined the average mass of an atom of an element as its _____ _____

Answer 1

we defined the average mass of an atom of an element as its atomic mass .

Question 2

We now define the average mass of a molecule (or a formula unit) of a compound as its _____ ____

Answer 2

We now define the average mass of a molecule (or a formula unit) of a compound as its formula mass

Question 3

For any compound, the formula mass is the sum of the atomic masses of all the atoms in its _____ _____.

Answer 3

For any compound, the formula mass is the sum of the atomic masses of all the atoms in its chemical formula.

Question 4

Calculate the formula mass of glucose, C6H12O6 .

Answer 4

To find the formula mass, add the atomic masses of each atom in the chemical formula:

Formula mass

= 6 * (atomic mass C) + 12 * (atomic mass H) + 6 * (atomic mass O)

= 6(12.01 amu) + 12(1.008 amu) + 6(16.00 amu)

= 180.16 amu

Question 5

We then used the molar mass in combination with ________ number to determine the number of atoms in a given mass of the element.

Answer 5

We then used the molar mass in combination with Avogadro’s number to determine the number of atoms in a given mass of the element.

Question 6

The same concept applies to ________. The molar mass of a ________— the mass in grams of 1 mol of its ________ or ________ units—is numerically equivalent to its formula mass.

Answer 6

The same concept applies to compounds. The molar mass of a compound— the mass in grams of 1 mol of its molecules or formula units—is numerically equivalent to its formula mass.