L.6 Stoichiometry

Question 1

Empirical Formula

Molecular Formula

Structural Formula

Answer 1

Only the rations/proportion of atoms in the molecule

The actual specific number of atoms in the molecule

Actual structure of molecule

Question 2

What is a mole? Avogadro’s number?

Answer 2

Amole is a quantity of any substance that is equal to the number of particles that are found in 12 grams of carbon 12

6.022 X 10^-23 mol

Question 3

Molecular weight

Answer 3

is the mass (in amu) of the constituent atoms in a compound as indicated by the molecular formula

H2O

H = 1 amu x 2 = 2

O = 16 amux 1 = 16

Total = 18 amu per molecule

Question 4

Molar mass

Answer 4

The mass on one mole of a compound; usually measured in grams per mole

Moles = Mass of sample / molar mass

Question 5

Gram equivalent weight

Answer 5

is a measure of the mass of a substance that can donate one equivalent of the species of interest (protons, ions, hydroxides, electrons).

GEW = Molar mass/ n

n = number of particles of interest produced or consumed per molecule of the compound in the reaction

ex; H2CO3

n= 2 (hydrogen ions)

Question 6

Normality

Answer 6

is the ratio of equivalents per liter; it is related to molarity by multiplying the molarity by the number of equivalents present per mole of compound.

Molarity from normality: Molarity = Normality / n

n = number of particles of interest produced or consumed per molecule of the compound in the reaction

ex; H2CO3

n = 2 (hydrogen ions)

Question 7

Percent composition

Answer 7

% composition = Mass of element in formula / molar mass x 100

Question 8

Percent Yield

Answer 8

percent yield = Actual yield/theoretical yield x 100

Question 9

Equivalents

Answer 9

If the amount of a compound is a reaction is known and we need to determine how many equivalents are present, use the equation

Equivalents = mass of compund / gram equivalent weight