Chemistry 131 Test 2

SI unit for amount of substance
Avogadro’s Number
6.022 x !0^23
the mole lets us relate
the number of entities to the mass of a sample of those entities
molar mass
the mass per mole of its entities and has units of grams per mole
moles to atoms
multiply by 6.022 x 10^23 atoms/mol
mass % or element X =
((moles of X in formula x molar mass of X (g/mol))/ (grams of 1 mol of compound)) x100
mass of an element
mass of compound x ((mass of element in 1 mol of compound) / (mass of 1 mol of compound))
a mole of substance is
the amount that contains Avogadro’s number of chemical entities
empirical formula shows
the lowest whole number of moles, and thus the relative number of atoms
molecular formula shows
the actual number of atoms of each element in a molecule
structural formula shows
the relative placement and connections of atoms in the molecule
combustion analysis is used to measure
the amounts of carbon and hydrogen in a combustible organic compound
two or more compounds with the same molecular formula but different properties
chemical equation shows
the identities and qualities of substances of substances in a chemical or physical change
theoretical yield
amount of product calculated from the molar ratio in the balanced equation
actual yield
the amount of product actually obtained
theoretical and actual yields are expressed in units of
amount (moles) or mass (grams)
% yield =
(actual yield / theoretical yield) *100
substance being disolved
solution dissolving the solute
molarity =
mol solute / L solution
water’s great solvent power arises from ______ and ______ which create _________
the uneven distribution of electron charge and a bent molecular shape which create a polar molecule
covalent bond
electron sharing
ionic bond
electron transfer
what makes a polar molecule
combination of polar bonds and a bent shape
water separates ions by
replacing attractions with others between several water molecules and each ion
surrounded closely by solvent molecules
soluble ionic compounds are electrolytes
the ions are free to move, and thus, the solution conducts electricity
three types of equations to represent aqueous ionic reactions
molecular equations
total ionic equations
net ionic equations
molecular equations shows
all the reactants and products as if they were intact undissociated compounds
total ionic equations show
all the soluble ionic substances dissociated into ions
spectator ions
ions that are unchanged on both sides of the equation
net ionic equations shows
only the actual chemical change by eliminating the spectator ions
in a precipitation reaction
2 soluble ionic compounds react to form an insoluble product
insoluble product formed in a precipitation reaction
key event in a precipitation reaction
the formation of an insoluble product through the net removal of ions form solution
metathesis reaction or
double displacement reaction
acid-base reaction or
neutralization reaction
acid-base reaction occurs when
an acid reacts with a base
a substance that produces H+ ions when dissolved in water
a substance that produces OH- ions when dissolved in water
acidic solutions arise when
certain covalent H-containing molecules dissociate into ions in water
strong acids and bases
dissociate completely into ion
weak acids and bases
dissociate very little into ions
when no further change in the amounts of reactants and products occur
the reaction has reached a state of equilibrium
ionic compound that results from the reaction of an acid and a base
the acid-base reaction is a
proton transfer process
the known concentration of one solution is used to determine the unknown concentration of another
acid-base indicator
is a substance whose color is different in acid than in base
equivalence point occurs when
the amount (mol) of H+ ions in the original volume of acid has reacted with the same amount (mol) of OH- ions from the buret
end point occurs when
a tiny excess of OH- ions changes the indicator to its basic color (pink)
redox reaction or
oxidation reduction reaction
redox reactions include
the formation of a compound from its ELEMENTS (or the reverse process)
redox reaction is the
net movement of electrons from one reactant to another
loss of electrons
gain of electrons
oxidizing agent
the species doing the oxidizing (causing the electron loss)
reducing agent
the species doing the reducing (causing the electron gain)
the oxidizing agent is
the reducing agent is
H+ is typically the
reducing agent
oxidation number (O.N.)
the charge the atom would have if electrons were transferred completely, not shared
O.N. for group 1A
O.N. for group 2A
O.N. for Hydrogen
+1 with nonmetals
-1 with metals
O.N. for Oxygen
-1 with peroxides
-2 with everything else
O.N. for Fluorine
O.N. for group 7A
O.N. for metals in elemental form
oxidation is shown by
an increase in O.N.
reduction is shown by
a decrease in O.N.
transfer electrons are never free because
the reducing agent loses electrons and the oxidizing agent gains them simultaneously
three types of redox reactions
combination redox reaction
combining two elements
combining compounds and elements
combining two elements
metal and nonmetal form ionic compound
two nonmetals form a covalent compound
decomposition redox reaction
a compound forms two or more products, at least one of which is an ELEMENT
types of decomposition redox reactions
thermal decomposition
electrolytic decomposition
thermal decomposition
when the energy absorbed is heat
electrolytic decomposition
in the process of electrolysis, a compound absorbs electrical energy and decomposes into its elements
displacement redox reactions
the number of substances on the two sides of the equation remains the same, but atoms (or ions) exchange places
types of displacement redox reactions
double displacement
single displacement
double displacement redox reaction
atoms of two compounds exchange places
examples- precipitation, acid-base reactions
single displacement redox reaction
one of the substances is an element
the process of combining with oxygen, most commonly with the release of heat and the production of light, as in a flame
Hydrated Compounds
Compounds in which molecules of water are associated with the ions of the compounds
Law of Conservation of Matter
Matter can not be created nor destroyed
Indicates the number of moles involved in the reaction.
Stoichiometric Factor
Also known as the mole ratio. A ratio of the coefficients from two molecules in the balanced equation
Limiting Reactant
The reactant, that limits the amount of product produced.
Measuring Concentrations of Compounds in Solution Equation
M1 x V1 = M2 x V2
Aqueous Solutions
Solutions in which water is the solvent
types of Aqueous Solutions
Solubility Rules
All common salts of the Group 1A elements and ammonium are soluble.
All common acetates (CH3CO2-), nitrates (NO3-), perchlorates (ClO4-), and chlorates (ClO3-) are soluble.
All compounds of Group 7A elements (other than F) with metals are soluble except those of silver (Ag), mercury (Hg) and lead (Pb)
All compounds of F with metals are soluble except those of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and lead (Pb)
All sulfates are soluble except those of barium (Ba), strontium (Sr), lead (Pb), calcium (Ca), silver (Ag), and mercury (Hg).
Except for those in rule 1, carbonates (CO32-), hydroxides (OH-), oxides phosphates (PO43-), chromates (CrO42-) and sulfides are all insoluble
General properties of acids
Sour taste
Act corrosive
React with bases to form salt and water
general properties of bases
Bitter taste
Feel slippery
React with acids to form salt and water
The force exerted on an object divided by the area over which it is exerted.
1 atm = ___ mmHg
760 mmHg
Boyle’s Law
The Compressibility of Gases (when moles and temp are constant)
Boyle’s Law Equation
P1V1= P2V2
Charles Law
if a given quantity of gas is held at a constant pressure, its volume is directly proportional to the Kelvin temperature
Charles’ Law Equation
V1/T1 = V2/T2
According to Boyle’s Law, the volume of an amount of gas is
inversely proportional to the pressure
According to Charles’ Law, the volume of an amount of gas is
directly proportional to the Kelvin temperature at a costant pressure.
General or Combined Gas Law Equation
P1V1/T1 = P2V2/T2
Avogadro’s Hypothesis
the volume of a gas at a given temperature and pressure is directly proportional to the amount of gas in moles.
Ideal Gas Law Equation
R is
gas constant
R =
0.08201 L*atm/K*mol
The Density of Gases
The amount (n,mols) of any compound is given by its mass (m) divided by its molar mass (M).
Density of a gas equation
n is
the number of moles
n =
Partial Pressure
the pressure of each gas in the mixture
Dalton’s Law of Partial Pressure
the pressure of a mixture of ideal gases is the sum of the partial pressures of the different gases in the mixture.
Dalton’s Law of Partial Pressure Equation
Ptotal = P1 + P2 + P3…
Each gas in the mixture acts _______ and can therefore can be considered to behave as an ______.
independently of all of the others and can therefore be considered to behave as an ideal gas.
X1 is
the mole fraction
P1 =
The molecules in a gas sample do not ________
all move at the same speed.
All gases, regardless of their molecular mass, have the same ______ at the same ______.
average kinetic energy at the same temperature.
The average kinetic energy of gas particles is proportional to ____
the gas temperature.
the mixing of two or more gases due to their random molecular motions
the movement of a gas through a tiny opening in a container into another container where the pressure is very low.
Graham’s Law
The rate of effusion of a gas is inversely proportional to the square root of the mass of its particles.
_______ molecules with _______ average speeds strike the barrier more often and pass more often through it
Lighter; higher
Van der Waals Equation
developed to take into account the cases in which the ideal gas equation breaks down.
the mixing of two or more gases due to their random molecular motions
gas volume changes significantly with
pressure and temperature
increasing the force on the piston ____ the gas volume
gas flows very
gases have ____ densities
pressure is
the force exerted per unit of surface area
pressure =
force / area
used to measure atmospheric pressure
1 atm = ___ mmHg
760 mmHg
1 torr = ____ mmHg
1 mmHg
Si unit of pressure
Pascal (Pa)
ideal gas
one that exhibits linear relationships among volume, pressure, temperature and amount of gas
0*C (273.15 K) and 1 atm (760 torr/ mmHg)
standard molar volume
22.4 L
r =
0.0821 L*atm/ K*mol
V =
nRT/ P
n =
m/M or PV/RT
density =
MP/RT or m/V
M =
Ptotal =
P1 + P2 + P3 ….
P1 =
X1 x Ptotal
X1 = mole fraction (n1/ntotal)
Postulates of Kinetic Molecular Theory
Postulate 1: Particle volume – assumed to be zero
Postulate 2: Particle motion – constant random straight line
Postulate 3: Particle collision – elastic
temperature is a measure of
the average kinetic energy of a particle
Graham’s Law of Effusion
the rate of effusion of a gas is inversely proportional to the square root of its molar mass
the movement of one gas through another
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