FINAL EXAM- The Mole

Question 1

Atomic mass unit

Answer 1

A unit of mass that describes the mass of an atom or molecule; it is exactly 1/12 of the mass of a carbon-12 atom.

Question 2

Formula unit

Answer 2

a particle of an ionic compound.

Question 3

Molecule

Answer 3

a particle of a covalent compound.

Question 4

Atom

Answer 4

a particle of an element.

Question 5

Mole

Answer 5

The SI base unit used to measure the amount of a substance whose nuber of particles is the same as the number of atoms of carbon in exactly 12 grams of carbon-12.

Question 6

Avogadro’s number

Answer 6

6.02 X 1023, the number of atoms or molecules in 1 mol.

Question 7

Molar mass

Answer 7

The mass in grams of 1 mol of a substance (found on periodic table).

Question 8

Empirical formula

Answer 8

a chemical formula that shows the composition of a compound in terms of the relative numbers and kinds of atoms in the simplest ratio (simplest whole number ratio of atoms in a compound).

Question 9

Molecular formula

Answer 9

gives the actual number of atoms of each element in the compound

Question 10

Percentage composition

Answer 10

The percentage by mass of each element in a compound.

Question 11

Molar mass

Answer 11

list and add

Question 12

Determine empirical formulas

Answer 12

• How to recognize: will ask for the empirical formula
• How to solve:
• For each element, write the mass of the element/1 and multiply by 1 mol element/atomic mass and label them g element
• Take those numbers, divide each one by the smallest one out of all of them
• If numbers are in whole number ratios, use that as the subscripts in your formula, if not, multiply them to get the smallest whole number ratio and use that
• Problems like 13 and 15 give the percent compositions of each element but not the mass. In this case, use percent composition (percent, divide by 100, multiply by total mass of compound/denominator) to find the masses, then use those as you normally would

Question 13

Determine molecular formulas

Answer 13

• How to recognize: will ask for molecular formula
• How to Solve:
• Follow the exact same steps from H to determine the empirical formula
• Use the empirical formula to find the mass of the empirical formula and see if it matches the mass of the compound
• To do this, take the mass of the compound and divide it by the mass you got
• Multiply the subscripts of each of the elements by that number to get the molecular formula
• If this number is one, you already have the molecular formula (empirical and molecular are the same in this case)

Question 14

General conversion factors

Answer 14

• Given value/1
• Molar mass/1 mol compound
• Avogadro’s number, particle/1 mol compound
• For determining molecular and empirical formulas, use the third conversion factor just with elements instead, so Atomic mass (number from periodic table)/1 mol element