Chem 1120 Summer Exam 3 Study Guide

exothermic

a process or reaction which releases heat to the surroundings is said to be

exothermic

A reaction is said to be ____ if the bonds formed during the reaction are stronger than the bonds broken

endothermic

a process or reaction that absorbs heat and has a positive enthalpy change

heat of reaction (enthalpy change)

the difference between the energy absorbed in breaking bonds and that released in forming bonds

increase; number of moles; pressure and temperature

according to avogadro’s law, the volume of a gas will ____ as the ____ is increased while the ____ are held constant

boyle’s law

P1 V1 = P2 V2

charles’s law

V1/T1 = V2/T2

gay-lussac’s law

P1/T1 = P2/T2

combined gas law

P1 V1/T1 = P2 V2/T2

avogadro’s law

V1/n1 = V2/n2

ideal gas law

PV = nRT

activation energy can best be described as

the difference in energy between reactants and the maximum energy

as the temperature of a liquid is lowered, what happens to its vapor pressure?

its vapor pressure drops

at a high altitude water boils at 95 C instead of 100 C at sea level because

the atmospheric pressure is less

entropy

the amount of disorder in a system

how will the volume of a fixed sample of gas change of its pressure is doubled and the kelvin temperature is doubled?

it will not change

in comparing liquids and gases, liquids have ____ compressibility and ____ density

smaller; greater

exergonic

a spontaneous reaction or process that releases free energy and has a negative Gibbs free energy

endergonic

 a nonspontaneous reaction or process that absorbs free energy and has a positive Gibbs free energy 

reaction rates

the rate of a chemical reaction is how fast the reactants are consumed or products are produced in a given time period

what are the 4 factors that influence the rate of chemical reactions

physical nature of the reactants

reactant concentration

reaction temperature

catalyst

the scientific principle which is the basis for balancing chemical equations is

the Law of conservation of mass

the total pressure of a mixture of gases is

the sum of the partial pressures of the components

london forces

weakest

the larger the molar mass the greater the forces

caused by movement of electrons

dipole-dipole

permanent and stronger than london forces

which combination of characteristics is most likely to be associated with molecules have strong dipole-dipole interactions?

1. polar bond

2. asymmetric shape

3. relatively low boiling point

4. large surface area

1 and 2

what is a liquid

definite volume; shape of container; moderate intermolecular attractions

what pair of molecules have the strongest dipole-dipole interactions?

NH3 and NH3

which process is exothermic/

gas —> liquid

what best describes the way a catalyst works?

it decreases the value of E_act

potential energy

stored energy

kinetic energy

the energy of motion

law of conservation of energy

energy can be neither created nor destroyed in any physical or chemical change 

bond dissociation energy

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

spontaneous process

a process that once started proceeds without any external influence

entropy

the symbol S is used for entropy, and it has the unit of cal/mole K. The physical state of a substance and the number of particles have a large impact on the value of S

free energy change

used to describe the spontaneity of a process. It takes both the enthalpy change and the entropy change into account

molecular collisions

reactant particles must interact, collide to react

activation energy

for the collision to lead to a reaction, the particles have to have a minimum amount of kinetic energy

collision orientation

the particles must be lined up properly when they collide to produce a reaction 

catalyst

a substance that increases the rate of reaction without being consumed in the reaction

the catalyst holds

1. one reactant in a particular orientation

2. weakens the bonds where the reaction takes place

   1. brings the reactants together more efficiently

chemical equilibrium

the process where two opposing chemical reactions occur simultaneously at the same rate

potential energy is…

a cohesive force

kinetic energy is...

a disruptive force