Chemistry Test 4

Avogadro’s Number
6.022 x 1023
molar mass (molecular weight)
the mass in grams of one mole of a substance
mass fraction of a given element

mass of the element in one mole of compound

;


mass of one mole of the compound

;

Empirical Formula
tells the relative # of atoms of each element it contains. the simplest whole # ratio of atoms in a compound
molecular formula
the exact formula of a molecule, giving the types of atoms and the # of each type
whole-number multiple

molecular weight


empirical formula weight

rounding rule
to arrive at the nearest whole number, the number must be within 0.2 to round up or down
mole ratio
the ratio of moles of one substance to moles of another substance in a balanced equation
stoichiometric quantities
the exact amount of reactants that is used so that all of the reactants will run out (used up) at the same time
limiting reactant (reagent)
the reactant that is consumed first and limits the amounts of product formed
theoretical yield
the amount of a product formed when the limiting reagent is completely consumed
actual yield
the amount of product actually obtained
percent yield
actual yield/theoretical yield x 100
visible light region
400 – 700 nm
continuous spectrum
a spectrum that exhibits all the wavelenths of visible light (white light pass through a prism)
line spectrum
a spectrum that contains certain specific wavelengths which are characteristic of a substance emitting those wavelengths
wavelength
the distance between two consecutive peaks or troughs in a wave
frequency (v)
the given number of waves (cycles) per second that pass through a given point in space
speed (c)
indicates how fast a given peak moves through space
long wavelength
low frequency
short wavelength
high frequency
particles
have mass and position in space specified
waves
massless and delocalized, position in space could not be specified
Plank’s Constant
6.626 x 10-34
Compton Effect
the transfer of energy from the photon to the electron
Conclusions from Plank & Einstein

1. Energy is quantized. It can only occur in discrete units called quanta.

2. Electromagnetic radiation, which was previously thought to exhibit only wave properties, seems to show certain characteristics of particulate matter as well.  This phenomenon is sometimes referred to as the dual nature of light

Louis de Broglie
investigated the dual nature of matter and discovered an equation which allows us to calculate the wavelength of a particle
Defraction
the scattering of light from a regular array of points or lines, producing contructive and destructive interference
CJ Davisson and L.H. Germer
directed a beam of electrons at a Ni crystal, and observed a diffraction pattern similar to x-ray defraction
high-energy photon
short wavelength of light
low-energy photon
long wavelength of light
quantized
only certain values are allowed for energy levels
Neils Bohr
developed quantum model for the H atom. proposed that the electron in a H atom moves around the nucleus only in certain allowed circular orbits. calculated the radii for these allowed orbits by knowing that particles in motion tend to move in a straight line and can travel in a circle only by application of a force toward the center of the circle
molecular formula

molar mass


empirical formula mass

Planck’s constant (h)
6.626 x 10-34J*s
change in energy

nhv

h = planck’s constant

v = frequency of electromagnetic radiation

Energy of a photon

hv

 

or

 

hc

___________

 

wavelength

mass

E/c2

e = energy

c = speed of light

 

(hc/wavelength)/c2

 

h/(wavelength*c)

Broglie’s equation
m = h/(wavelength*velocity)

Bohr’s equation

(change in energy of an electron when it changes orbits)

-2.178 x 10-18J(Z2/n2)
change in energy of an atom
energy of final state – energy of initial state
wavelength of photon
hc/change in E
x

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