Studied by 13 people
energy diagram
a graph showing the changes in potential energy during a reaction. It starts with the reactants on the left and proceeds to the products on the right
Ea
activation energy; the amount of energy that is required to start the reaction. the difference in potential energy between the reactants and the top of the ‘curve’.
ΔH
enthalpy; the difference in potential energy between the products and reactants
transition state
the high energy stage between the reactants and the products. rearranging of atoms has started, but not completed yet. also referred to as the activated complex.
endothermic
gets colder
reactants have less potential energy compared to products
energy was absorbed during this reaction (this is why the products have more energy)
ΔH will be positive
thermal → potential energy
exothermic
gets warmer
reactants have more potential energy compared to products
energy was released during this reaction (this is why the products have more energy)
ΔH will be negative
potential → thermal energy
did this reaction absorb or release more energy?
absorb
what type of reaction does this graph represent?
endothermic
which of the letters a-f in the diagram represent the potential energy of the products?
E
which of the letters indicate the potential energy of the transitional state?
C
which letter indicates the potential energy of the reactants?
A
which letter indicates the activation energy (Ea)?
B
which letter indicates the heat of reaction (Δ H)?
F
did this reaction absorb or release more energy?
absorb
what type of reaction does this graph represent?
endothermic
what is the quantitative value for the potential energy of the reactants?
80 kJ
what is the quantitative value for the potential energy of the products?
160 kJ
what is the numerical value for the activation energy (Ea)?
Ea = (240 kJ - 80 kJ) = 160 kJ
what is the numerical value for heat of reaction (Δ H)?
Δ H= 160 kJ - 80 kJ = 80 kJ
what is the potential energy of the transitional state?
240 kJ
compound
2 or more elements that are chemically combined (not just mixed)
metal + metal
metallic compound
metal + nonmetal
ionic compound
nonmetal + nonmetal
molecular compound
ion formation
each element has one particular ion it nearly always forms, when it bonds in an ionic compound (except for transition metals, which had multiple preferred ionic states).
in general, the ion an element will form can be predicted by the _____.
octet rule
octet rule
when an element forms an ion, it will do so in whatever way allows it to have a full outer shell (8 valence electrons) the easiest
ionic compound
consists of positive and negative ions that are held together in a crystal lattice
crystal lattice
a rigid geometric pattern
the forming of ionic compounds
Generally, any compound containing a metal and a nonmetal is an ionic compound.
The compound forms when the metal atom gives an electron to the nonmetal atom. T
The metal atom becomes a positive ion (cation) and the nonmetal atom becomes a negative ion (anion).
the net charge of an ionic compound should always be ____.
zero
chemical nomenclature
a set of rules that all chemists agree upon to allow us to consistently name compounds
steps to name ionic compounds
name the positive ion, then the negative ion
the name of the positive ion is the same as the name of the atom. Ex: Mg2+ is the “magnesium” ion
the name of the negative ion has the “ide” ending. Ex: Cl-1 is the “chloride” ion
if the positive ion is a transition metal, you must include the charge of the atom as a Roman numeral in parentheses. Ex: Cr+4 is the “chromium (IV)” ion
chemical formulas
tell how many of each atom (or ion) are in a compound. when writing chemical formulas, subscripts are used to note that the smallest whole number ratio of ions in a ionic compound. (the positive ion is always written first in the ionic compound.")
how to write formulas for ionic compounds
determine the charge of each ion
determine how many of each ion are in the compound. (cross the charges for a short cut)
write the positive ion, then the negative ion. don’t write their charges, but do use a subscript to tell how many there are
roman numerals
one: I
two: II
three: III
four: IV
five: V
six: VI
practice: when potassium and oxygen form a compound
what ion does potassium form? symbol: K+ name: potassium
what ion does oxygen form? symbol: O-2 name: oxide
there are 2 potassium ions for every oxide ion
name the compound: potassium oxide
compound formula: K2O
practice: when calcium and sulfur form a compound
what ion does calcium form? symbol: Ca+2 name: calcium
what ion does sulfur form? symbol: S-2 name: sulfide
there is a calcium ion for every sulfide ion
name the compound: calcium sulfide
compound formula: CaS
polyatomic ions
groups of atoms that have bonded together and that have an overall charge. ex: SO4^-2 means that in one sulfur ion, there is one sulfur atom and 4 oxygen atoms and their overall charge is -2.
molecular compounds
formed by two nonmetals
composed of discrete molecules
since nonmetals “need” to gain electrons to become more stable, they can share electrons to form molecular compounds
called covalent bonding
these compounds may exist as solids, liquids, or gases at room temp
usually have lower melting points than ionic compounds
molecular compounds nomenclature
name each element
use a prefix to indicate the number of each atom there are in a molecule
for the first element, if there is only one atom in each molecule, don’t use “mono”
change the ending of the last element to “ide”
prefix of molecular compounds
1 : mono
2 : di
3: tri
4: tetra
5 : penta
6 : hexa
SO3
sulfur trioxide
N2O5
dinitrogen pentoxide
when a metal and nonmetal bond, they form a ____
large crystal lattice
which one is a covalent compound?
Fe2O3
MgCl2
SeO
CaS
SeO
when cesium and phosphorous bond, there are
3 times as many Cesiums ions as Phosphorous ions
what is the right name for BaCl2
Barium Chloride
what is the right formula for Selenium Diflouride
SeF2
endothermic reaction make their environment ___
colder
which bonds are stronger in endothermic reactions?
reactant bonds
what represents activation energy in a reaction?
reactants → transitional state
a reaction was calculated to have absorbed +200 kJ/mol and released -600 kJ/mol. this reaction is…
exothermic
stronger bonds require….
high activation energy
which is stronger: ionic or covalent bonds?
ionic
intermolecular forces
forces of attraction between molecules
intramolecular forces
hold atoms together in a molecule
hydrogen bonds
attractive forces in which a hydrogen covalently bonded to a very electronegative atom causes attractions to other molecules
ionic bond
A chemical bond resulting from the attraction between oppositely charged ions.
covalent bond
A chemical bond that involves sharing a pair of electrons between atoms in a molecule
polar bond
a covalent bond between atoms in which the electrons are shared unequally
polar molecule
a molecule in which one side of the molecule is slightly negative and the opposite side is slightly positive
nonpolar bond
a covalent bond in which electrons are shared equally
nonpolar molecule
a molecule that does not have oppositely charged ends
Melting
change from a solid to a liquid
Freezing
\n The change of state from a liquid to a solid
Condensing
The change of state from a gas to a liquid
Vaporizing
the change from a liquid to a gas
Sublimation
A change directly from the solid to the gaseous state without becoming liquid
Deposition
\n a change directly from a gas to a solid
weakest intermolecular force
london forces
strongest intermolecular force
hydrogen bond
intermolecular forces between ALL polar molecules
dipole dipole forces
London forces are strongest for __________________ molecules
nonpolar
hydrogen bonds can form when H is bonded to __________
nitrogen, oxygen, or fluorine
Polar molecules will have ____________ boiling points than nonpolar molecules
higher
Nonpolar molecules will have __________ boiling points than polar molecules
lower
_________________ are the strongest of ALL forces
ionic bonds
Miscible
Describes two liquids that are soluble in each other
imiscible
liquids are not soluble in one another
lewis structure
simple models that show how atoms are connected in a molecule or polyatomic ion
note: lewis structure do NOT show the shape of a molecule, just how atoms are connect
each line represents 1 share pair of electrons
ionic bonds are stronger when
there are higher charges and the smaller the atoms
covalent bonds are stronger when
more electrons are shared
covalent network compound
crystal lattice w/covalent bonds ex: diamond
intermolecular force
a force of attraction between two molecules. these forces must be overcome during phase changes
dipole-dipole forces
the attraction between the partial positive end of one polar molecule, and the partial negative end of a different molecule
molecule MUST be polar to have this force
stronger when molecules are more polar (more uneven sharing it a big difference in electronegativity)
extra polar bonds: F-H, O-H and N-H
london dispersion forces
an attraction between TEMPORARY dipoles, that form because of the random motion of electrons within molecules
stronger when there are more TOTAL electrons (more polarizable)
covalent networks are the _____ type of compound to seperate
hardest
if there is the same electronegative difference between molecules, check ____
size
what does not affect lattice energy?
polarity
what is an example of an intramolecular force?
H-Cl
what property describes a strong bond?
high boiling point
what is an example of a non polar covalent compound?
CO2
T/F : non polar covalent bonds are stronger than ion-ion bonds
false
T/F: hydrogen bonds are stronger than London dispersion forces
true
what is the correct order of bond strength from strongest to weakest: ion-dipole, dispersion forces, H-bond
H-bond, ion-dipole, dispersion forces
what is a London dispersion force?
interaction between non polar molecules
what is an ion-dipole force?
interaction between an ion and polar molecule
what is an ion-ion force?
interaction between a cation and anion
what is hydrogen bonding?
interaction between polar molecules
Note 
Flashcard (37)