Chem #4 Flashcards
compound
pure substance composed of two or more elements in a fixed proportion
formula unit
the empirical formula of a compound (such as NaCl in which an actual molecule does not exist because it is just a big lattice structure).
formula weight
weight of the formula unit, adding up the atomic weights of the constituent ions according to its empirical formula.
molecular weight
the sum of the atomic weights of all the atoms in a molecule, and its units are atomic mass units (amu) per molecule.
o Atomic weight: weighted average of the masses of the naturally occurring isotopes of an element, not their weights.
mole
: a quantity of any substance (atoms, molecules, dollar bills, kittens) equal to the number of particles found in carbon-12.
o Number of particles is Avogadro’s number: 6.022 x 1023 mol-1
o Ex: one molecule of a compound has a mass of 62 amu and one mole of the compound has a mass of 62 grams.
molar mass
the mass of one mole of a compound (g/mol).
o Molecular weight is in amu/molecule
equivalent weights
how many moles of the thing we are interested in will one mole of a given compound produce
o Ex: HCl can donate one mole of H+ per mole of HCl
o Ex: Na can donate one mole of e- per mole of Na
o What it donates is known as the equivalent.
gram equivalent weight
the amount of a compound, measured in grams, that produces one equivalent of the particle of interest: = molar mass/n
n: the number of particles of interest produced or consumed per molecule of the compound in the reaction.
The mass that provides one mole of the particle of interest.
Equivalents = mass of compound / gram equivalent weight
Units are in grams/thing of importance (Ex: moles of H+)
normality
measure of concentration, given in the units of equivalents/L
Molarity = Normality / n
• n: the number of protons, hydroxide ions, electrons, or ions produced or consumed by the solute.
• Ex: monoprotic or diprotic acid
law of constant composition
any pure sample of a given compound will contain the same elements in an identical mass ratio
empirical formula
the simplest whole-number ratio of the elements in the compound
o CH2O is indicative of the empirical formula of a monosaccharide.
molecular formula
: the exact number of atoms of each element in the compound and is a multiple of the empirical formula.
percent composition
of an element by mass, the percent of a specific compound that is made up of a given element (all of this given element, could be three atoms of it).
o Percent composition = (mass of element in formula / molar mass) x 100
SPECIFIC COMPOUND
combination reaction
has two or more reactants forming one product.
o A + B C
decomposition reaction
: a single reactant breaks down into two or more products (usually as a result of heating, high-frequency radiation, or electrolysis.
o A B + C
combustion reaction
special type of combustion reaction that involves a fuel (usually a hydrocarbon) and an oxidant (normally oxygen). Involves oxidation of a fuel.
o CxHy + O2 CO2 + H2O
o Can use sulfur or other sugars as fuels.
Longer hydrocarbon chains yield ____
greater amounts of combustion products and release more heat in the process.
single-displacement reaction
an atom or ion in a compound is replaced by an atom or ion of another element.
o A + BC B + AC
o Common oxidation-reduction reaction
double-displacement reaction
displacement (metathesis) reaction: elements from two different compound swap places with each other to form two new compounds.
o AB + CD AD + BC
o Sometimes one of the products leaves as gas or does not dissociate (s)
o Neutralization Reactions: specific type of double displacement reaction in which an acid reacts with a base to produce a salt (and usually water)
metathesis = _____
another word for double displacement reaction
neutralization reaction
specific type of double displacement reaction in which an acid reacts with a base to produce a salt (and usually water)
law of conservation of mass
the mass of the reactants consumed must equal the mass of the products generated.
law of conservation of charge
The net quantity of electric charge, the amount of positive charge minus the amount of negative charge in the universe, is always conserved.
o Charge is same on both sides of the equation.
if stuck balancing a chemical reaction:
o IF STUCK, take a guess for the coefficient of the first element and then balance accordingly
