Chem Review- Exam 3

Energy

the ability to do work or produce heat

Reactions involve the

transfer of energy

Potential energy

stored energy

Kinetic energy

the energy of motion

According to the law of conservation of energy

energy can be neither created nor destroyed

when chemical bonds in the reactants break that’s

energy in

when new bonds form in the products thats

energy out

a triple bond is stronger than a

single bond and cannot be as easily broken

Bond dissociation energy

the amount of energy that must be supplied to break a bond and sperate the atoms in an isolated gaseous molecule

A process or reaction that absorbs heat is called an

endothermic reaction

a process or reaction that releases heat is called an

exothermic reaction

Heat of reaction or enthalpy change is

the difference between the energy of bonds broken in reactants and the energy of bonds formed in the products

exothermic reactoin

more energy released than absorbed, so the enthalpy number is negative

endothermic reaction

more energy absorbed than released so the enthalpy number is positive

spontaneous process

a process that proceeds without needing any external influence once it begins

non spontanous process

takes place only in the presence of a continuous external influence

free energy

energy that is available to do work

a spontaneous process is

exergonic and postive

a non spontanous process

energonic and negative

entropy

a measure of molecular disorder or randomness in a system

a gas has ____ than a solid

higher entrooy

a solid has ____ than gas

fewer moles of reactants

A chemical reaction will only occur if

the collisions between reactant molecules are sufficiently entergetic

activation energy

amount of energy necessary for a reaction to occur

the lower the activation energy,

the greater the number of productive collisoins in a given amount of time, so the faster the reaction

3 factors affect reaction rates

temperature, concentration and catalyst

many chemical reactions result in

the complete conversion of reactants into products

reversable reactions

never fully reach the completion point

chemical equilibrium

dynamic state in which the rate of foreward reaction is equal to the rate of the reverse reactoin

the equilbrium constant tells you

how far a reaction goes before reaching equilibrium

K < 0.001

only reactants are present at equilibrium

0.001<K<1

more reactants than products are present at equilibrium

1<K<1000

more products than reactants are present at equilibrium

K> 1000

only proudcts are present at equilbrium i

if only reactans are present at equilibrium than

no reaction occurs

if only products are present at equilibrium than

reaction goes to completion

Le chatelier’s principle

when a stress is applied to a chemical system at eqiuilibrium, the equilibrium shifts in the direction to relieve the applied stress

types of stress that can be appiled

change in concetratoin, temperature, and pressure

In an exothermic reactoin, if you increase the temperature

the eqiulibrium shifts to the left

in an exothermic reation if you decrease the temp

the equilibirum shifts to the right

in an endothermic reaction, if you increase the temp

the equilibirum shifts to the right

in an endothermic reaction, if you decrease the temperature,

the equilibrium shifts to the left

Regarding pressure, the equilibrium shifts toward the side with

fewer moles

Matter exists in 3 phases

gas, liquid and solid

every change of state is reversible and is characterized by changes in

enthalpy and entropy

melting point

the exact temperature at which entropy and enthalpy balance out

boiling point

represents the temperature at which liquid and gas co-exists in equilibrium

Intermolecular forces

the attractive forces between different molecules rather than within an individual molecule

forces within an individual molecule are called

intramolecular forces

in gasses, the IMF”s are

negligible

in liquids and solids

the stronger the IMF”s in a substance, the higher the melting and boiling point

3 types of IMF’s

london dispersion, dipole-dipole and hydrogen bonding

London Dispersion Forces

all molecules exist with this; non-polar molecules only have this

Dipole-Dipole Forces

the attractive force between positive and negative ends of polar molecuels; stronger than london dispersion

Hyrogen bonding

special type of dipole-dipole when an H atom bonded to an electrognetagive atom such as O,N or F; strongest IMF

Gasses are

highly compressible and occupy the full volume of their containers

when a gas is subjected to pressure

it’s volume decreases

gases allways form homogenous mixtures with

other gases

Kinetic- Molecular Theory of Gases gives us the

why not the how

pressure decreases at increasing

altitude because the number of gas particples in a given volume generally decreases with increasing altitude

common unit of pressure is

mmHg

the second unit of pressure is

atmosphere ( atm)

Atm is defined as

pressure required to support 760 mmHg in a column

the SI unit of pressure is

the pascal

Boyles law

the volume of a fixed quantity of gas at a constant temp is inversely proportional to its pressure

Charls’s law

the volume of a fixed quantity of gas at constant pressure is directly proportional to it’s aboslute pressure

Boyles law equaiton

P1V1=P2V2

Charles’s Law equation

V1/T1=V2/T2

Gay Lussac’s Law equation

P1/T1=P2/T1

The combined gas law equation

P1V1/T1 = P2V2/T2

Avogadro’s law

the voulume of gas at a constant temeprature and pressure is directly proportional to the number of moles of gas

Avogadro’s Law equation

V1/n1=V2/n2

molar volume

the volume occupied by 1 mole of a substance

standard temp

273.15 K

standard pressure

1 atm

the Ideal gas equation

PV = nRT

P=

the pressure in atm

V=

volume in liters

n=

gas quantity in moles

R=

0.08206 L.atm/ mol.K

T=

temperature in degrees kelvin

Daltons law of partial pressures

P(total) = P( gas 1) + P (gas 2) + P ( gas 3)

Real gasses and Ideal gasses are

NOT THE SAME

in endothermic reactions what side is heat on

involved on the reactant side

in exothermic reactions what side is heat on?

involved with the product side

what is the temperature where solid = liquid at equilibrium?

melting piont

what is the temp where liquid = gas at equilibrium?

boiling point

ionic compounds have higher __ than molecular compounds

melting and boiling points