Molecules and Moles

Question 1

Compounds

Answer 1

substances composed of 2 or more elements in a fixed composition

Question 2

Molecular Weight

Answer 2

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

the sum of the atomic weights of all the atoms in a molecule

amu/molecule
NOT: g/mol

Question 3

Molar mass

Answer 3

the mass of one mole (Avogadros # (6.022x10^23 particles)) of a compound; usually measured in grams per mol

g/mol

Question 4

Gram equivalent weight

Answer 4

A measure of the mass of a substance that can donate one equivalent of the species of interest

molar mass/n

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

Question 5

Normality

Answer 5

a measure of concentration (equivalents/L)

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

1N = contains a concentration of hydrogen ions equal to 1 mole per liter
2N = contains a concentration of hydrogen ions equal to 2 mole per liter

1 N HCl = 1 M HCl because HCl is a monoprotic acid
1 N H2CO3 = 0.5M H2CO3 because H2CO3 is a diprotic acid

always assume the retains proceed to completion

Molarity = Normality/n
n= # of particles of protons, hydroxide ions, electrons or ions produced or consumed by the solute

Question 6

Equivalents

Answer 6

How many moles of the thing we are interested in(protons, hydroxide ions, electrons or ions)
equivalents are most often seen in acid - base chemistry (hydrogen ions or hydroxide ions) and oxidation - reduction reactions (moles of electrons or other ions)

Sodium wil donate one mole of electrons (non equivalent) but magnesium will donate two more of electrons (two equivalents)

equivalents = mass of cmpd (g)/ gram of equivalent weight (g)

Question 7

Formula unit represents the

Answer 7

empirical formula of a compound

Question 8

If an acid is diprotic, how many equivalents of base are required to neutralize both protons and acid?

Answer 8

two

Question 9

If an acid is monoprotic, how many equivalents of base are required to neutralize both protons and acid?

Answer 9

one

Question 10

Law of constant comosition

Answer 10

states that any pure sample of a given copied will contain the same element in an identical mass ratio.

Question 11

Two ways to express the formula of a compound:

Answer 11

empirical formula

molecule formula

Question 12

empirical formula

Answer 12

gives the simplest whole number ratio of the elements in a compound

ex:
benzene empirical formula: CH
while the molecular formula is C6H6

Question 13

Molecular formula

Answer 13

gives the exact number of arms of each element in the compound and is a multiple of the empirical formula

ex:
benzene molecular formula is C6H6
while the empirical formula: CH

Question 14

Percent Composition

Answer 14

the percent of a specific compound that is made up of a given element

Formula:
% composition= (mass of element in formula/molar mass) x 100