Purdue CHM 115 exam 2

exothermic process

releases heat to the surroundings; water gains any heat lost by the system

endothermic process

absorbs heat from the surroundings;water loses any heat gained by the system

wavelength

distance between successive wave crests

frequency

number of wavelengths that pass per unit of time

energy

directly proportional to frequency

electromagnetic spectrum

includes all forms of electromagnetic radiation

increases

as the wavelength of the electromagnetic radiation decreases, the energy _______

highest

Gamma rays have the shortest wavelengths, and thus, they are the __________ energy form of electromagnetic radiation

lowest

Radio waves have the longest wavelengths, and thus, they are the ________ energy form of electromagnetic radiation

absorption

occurs when an electron goes from a lower‑energy shell to a higher‑energy shell

emission

occurs when an electron goes from a higher‑energy shell to lower‑energy shell

bond energy

amount of energy required to dissociate, or break, a bond into its component ions.

blank

used to remove signals due to the cuvette walls and the solvent used in the sample

1

1Al: __alum

speed of light

c; constant in vacuum that equals 3.00 × 10^8 m/s

Rydberg Equation

a mathematical description to fit hydrogens atomic spectra

cathode rays

rays emanating from the cathode in an electrical discharge

Bohr orbits

describes the physical motion and positions of electrons

stationary states

the H atom has only certain energy levels, which Bohr called ____________

ground state

when the electron is in the 1st orbit, the atom is of the lowest energy

the energy of the photon (hv)

the difference between the energies of the two states

excited state

when electron is in any orbit higher than n=1, the atom is in an _________

Bohr equation

describes the energies of line spectra

internal energy

______________ of a system is the sum of all potential and kinetic energy components

system

what we are studying

everything besides the

energy transferred when an object is moved aagainst a force

energy transferred from hotter objectss to a cooler one

work + heat

total ∆

change by system

volume increases

change on system

volume decreases

∆H

heat released or absorbed at constant pressure, qp

exothermic process

-qp and -∆H is when energy is leaving the system or released from the system

endothermic process

+qp and +∆H is when energy enters the system

change in internal energy < 0

the energy released to surroundings; -heat and -∆H

exothermic process

heat given out; ∆H < 0

∆E > 0

energy absorbed from surroundings; + heat and +∆H

endothermic

heat taken in; ∆H > 0

change in internal energy < 0

work done by system; w < 0

∆E > 0

work done on system; w > 0

+ ∆E

+q and +w

-∆E

-q and -w

state function

a property of a system that depends only on the state of the system and not on the path used to get there

path function

a property that depends on the path taken to reach a state

state function

value of _______ depends on the state of the system, not how we arrived at that state

path functions

work and heat are _______

specific heat capacity (c)

_____________ of a substance is the quantity of heat required to change the temp. of 1 gram of the substance by 1 K

calorimetry

measuring calories

coffee-cup calorimeter

this device measures the heat transferred at constant pressure (qp)

enthalpy change

the heat released or absorbed at constant pressure

∆H

change in heat for a system at constant pressure

exothermic

heat is given out; ∆H < 0

endothermic

heat taken in; ∆H > 0

thermochemical equation

a balanced equation that ˙=∆== reaction

magnitude

the ________ of change in enthalpy is proportional to the amount of substance

Hess’s Law

states that the enthalpy change of an overall process is the sum of the enthalpy changes of its individual steps

standard heat of formation

the enthalpy change for the formation of 1 mole of a compound from its constituent elements in their “standard states”

standard state

the form of the element found in nature at 1 atm and 25ºC

∆E

change in energy of the atom (energy of the emitted photon)

n(final)

integer; final distance from the nucleus

n(initial)

integer; initial distance from the nucleus

Bohr Equation

describes the energies of the line spectra

bohr orbits

Bohr model uses _________ to describe the physical motion and position of electrons and incorporates the concept of quantized energy levels'; worked well to account for spectra of one-electron systems

electrons

sub-atomic particles

photons

light energy is quantizied

particle-wave duality

photons/electrons have characteristics of waves and particles

de Broglie

distinction of particles and waves only works at the macroscopic level

Heisenberg

uncertainty principle

electrons

described mathmatically using a wave function (Psi) from which we can determine properties of electrons

principal quantum numbers (n)

describes the size of the orbital or energy level of the atom

angular quantum number (l)

sublevels; describes the shape of the orbital

magnetic quantum number (m)

describes an orbitals orientation in space

spin quantum number (s)

describes the spin or direction (clockwise or counter-clockwise) in which an electron spins

integer values

used to specify shell/size/level the electron is in

s orbital

l 0

p orbital

l 1

d orbital

l 2

f orbital

l 3

nodes

zero probability of finding electrons (other than origin)

orbital shapes

result from different characteristics of the electron

principal quantum number (n)

describes the size or the orbital or energy level of the atom

angular quantum number (l)

sublevels; describes the shape of the orbital

magnetic quantum number (m)

describes an orbital’s orientation in space

homogenous mixture of two or more substances

solution

greater amount of solution

solvent

lesser amount of solution

solute

concentration

the quantity of solute per quantity of solvent or quantity of solution is referred to as concentration

water

a polar solvent that can dissolve many ionic compounds to generate solvated ions as well as polar molecules

strong electrolytes

compounds that dissociate extensively in aqueous solutions

non-electrolytes

substances that dissolve in water but do not ionize (no ions produced)

concentration

relative amount of solute and solvent in the solution

dilute

relatively small amount of solute

concentrated

relatively large amount of solute

saturated

largest amount of solute possible in that solvent at that temperature

supersaturated solution

contains more solute than the maximum expected in that solvent at that temperature

molarity

ma ost common measure of concentration used by chemists for liquid solutions is the number of moles of solute per liter of solution

concentrated solution

more solute particles are present per unit volume

dilute solution

the same number of solute particles are present in the larger volume, so fewer solute particles are present per unit volume

spectrometer

measures how much light is absorbed at each wavelength across the UV and visible range

Beer-Lambert Law

idea that the amount of light transmitted through a red solution decreases for more concentrated solutions