Chemistry Honors - Moles Test

Mole

a very big number (6.02 x 10^23) used to count / measure things

6.02 x 10^23

Avogadro's number

6.02 x 10^23 atoms / 1 mole

What conversion factor can be used to convert between moles and atoms of an element?

Avogadro's hypothesis

if we have the same number of particles of any two gases at the same temperature and pressure, then they will have the same volume

Standard Temperature and Pressure (STP)

0 degrees Celsius and 1 atmosphere of pressure

1 mol / 22.4 L

What conversion factor can be used to convert between moles and volume of a gas at STP?

Molar Mass

the mass of one mole of an element's atoms

the molar mass of an element is the same as its atomic mass

How can you find the molar mass of an element?

multiply the molar mass of each element by its subscript, then add it all up

How can you find the molar mass of a compound?

1 mol / molar mass (g)

What conversion factor can be used to convert between moles and grams of an element or compound?

Percent Composition

the percent, by mass, of each element in a compound

Multiply the mass of the compound by the element's percentage.

How do you find the mass of the elements in a compound?

Determine the compound's molar mass, then take the molar mass of each element and divide it by the whole molar mass.

How do you theoretically calculate the percent composition of a compound?

Hydrate

a compound that contains water molecules in its formula

Heat the compound with a Bunsen Burner until all the water boils away, then divide the mass of the water that was lost by the mass of the original compound.

How do you experimentally calculate the percent of water in a hydrate?

Empirical Formula

a formula with the lowest whole-number ratio of elements in a compound

Assume that you have 100g of the substance (this will automatically make your percents into grams), convert the grams into moles, write the number of moles as subscripts in your chemical formula, and divide each subscript by the smallest one, to make them into whole numbers.

How do you determine the empirical formula from percent composition?