Monday, November 19, 2012
CHEMISTRY, CHEMICAL ENGINEERING: Periodic Table Elements  Roots, Origin, Etymology of Names
A
Actinium Ac  aktis = ray
Aluminum Al  alumen = substance with astringent taste
Americium Am  America (country or continent)
Antimony Sb  antimonos = opposite to solitude
Argon Ar  argos = inactive
Arsenic As  arsenikon = valiant
Astatine At  astatos = unstable
B
Barium Ba  barys = heavy
Berkelium Bk  Berkeley (University of California)
Beryllium Be  beryllos = a mineral
Bismuth Bi  bisemutum = white mass
Boron B  bawraq = white, borax
Bromine Br  bromos = stink, stench
C
Cadmium Cd  cadmia = calamine, a zinc ore
Calcium Ca  calcis = lime
Californium Cf  State and University of California
Carbon C  carbo = coal
Cerium Ce  Ceres = the asteriod
Cesium Cs  caesius = sky blue
Chlorine Cl  chloros = grass green
Chromium Cr  chroma = color
Cobalt Co  kobolos = a goblin
Copper Cu  cuprum = copper
Curium Cm  Marie & Pierre Curie (French physicists)
D
Dysprosium Dy  dysprositos = hard to get at, difficult to access, hard to obtain, rare earth
E
Einsteinium Es  Albert Einstein (German theoretical physicist)
Erbium Er  Ytterby = town in Sweden where it was discovered
Europium Eu  Europe (continent)
F
Fermium Fm  Enrico Fermi (Italian physicist)
Fluorine F  fluere = to flow
Francium Fr  France (country)
G
Gadolinium Gd  Johan Gadolin (Finnish chemist)
Gallium Ga  Gaul (historic France)
Germanium Ge  Germany (country)
Gold Au  aurum (AngloSaxon, Latin "gold")
H
Hafnium Hf  Hafnia (city of Copenhagen, Denmark)
Helium He  helios = sun
Holmium Ho  Holmia (city of Stockholm, Sweden)
Hydrogen H  "hydro genes" = water former
I
Indium In  indicum = indigo spectrum line
Iodine I  iodes = violet spectrum line
Iridium Ir  iridis = rainbow
Iron Fe  Anglo Saxon "iren", Latin "ferrum"
K
Krypton Kr  kryptos = hidden
L
Lanthanum La  lanthanien = to be concealed
Lawrencium Lw  Earnest Lawrence (American nuclear physicist, writer, inventor of cyclotron)
Lead Pb  Anglo Saxon lead, Latin plumbum
Lithium Li  lithos = stone
Lutetium Lu  Lutetia = ancient name of Paris, France
M
Magnesium Mg  magnes = magnet
Mendelevium Md  Dmitri Mendeleev (Russian chemist and inventor, devised periodic table)
Mercury Hg  Mercury, messenger of the gods (mythology) ; "hydrarygus" = liquid silver
Molybdenum Mo  molybdos = lead
N
Neodymium Nd  from two Greek words: neos = new; didymos = twin
Neon Ne  neos = new
Neptunium Np  named after the planet Neptune
Nickel Ni  from German "kupfernickel", false copper
Niobium Nb  Niobe = mythological daughter of Tantalus (Greek mythology)
Nitrogen N  from two Latin words: nitro = native soda; gen = born
Nobelium No  Alfred Nobel (Swedish chemist, engineer, innovator, armaments manufacturer and the inventor of dynamite)
O
Osmium Os  Greek: osme = odor of volatile tetroxide
Oxygen O  from two Greek words: "oxys" = sharp; "gen" = born
P
Palladium Pd  named after the planetoid Pallas
Phosphorus P  phosphoros = light bringer
Platinum Pt  from Spanish "plata", meaning silver
Plutonium Pu  named after the planet Pluto
Polonium Po  Poland (country of Marie Curie, codiscoverer of the element)
Potassium K  Latin "kalium", English potash
Praseodymium Pr  from Greek: Praseos = leek green; didymos = twin
Promethium Pm  Prometheus = fire bringer (Greek mythology)
Protactinium Pa  protos = first
R
Radium Ra  Latin "radius" = ray
Radon Rn  from Radium (the element Radon is formed by radioactive decay of radium)
Rhenium Re  Rhenus = Rhine province of Germany
Rhodium Rh  rhodon = a rose
Rubidium Rb  rubidus = red
Ruthenium Ru  Ruthenia (Latinized form of Russia) = region of western Ukraine south of the Carpathian Mountains
S
Samarium Sm  Vasili SamarskiBykhovets, a Russian mining engineer
Scandium Sc  Scandinavia
Selenium Se  selene = moon
Silicon Si  silex = flint
Silver Ag  Latin "argentum", AngloSaxon, siolful
Sodium Na  Latin "natrium"; "sodanum" = cure for headaches
Strontium Sr  town of Strontian, Scotland
Sulfur S  Latin: sulphur, sulpur, sulfur = brimstone
T
Tantalum Ta  Tantalus (Greek mythology)
Technetium Tc  technetos = artificial
Tellurium Te  tellus = the earth
Terbium Tb  Ytterby (town in Sweden)
Thallium Tl  thallos = young shoot
Thorium Th  Thor (Scandinavian mythology)
Thulium Tm  Thule = northern part of habitable world
Tin Sn  Latin "stannum", Tinia (Etruscan god)
Titanium Ti  Titans (Greek mythology: The Titans were the first sons of the earth)
Tungsten W  symbol from German "worfram"; from Swedish: "tung sten" meaning heavy stone
U
Uranium U  named from the planet Uranus
V
Vanadium V  Vanadis (goddess of Scandinavian mythology)
X
Xenon Xe  from Greek "xenos" = strange
Y
Ytterbium Yb  Scandinavian: Ytterby (a town in Sweden)
Yttrium Y  Scandinavian: Ytterby (town in Sweden)
Z
Zinc Zn  German "zink", "zinn" meaning tin
Zirconium Zr  zircon = mineral
Saturday, November 17, 2012
Thermodynamics: PV Work: compressionexpansion work
derivation of PV work formulas
1. isobaric conditions: p = c
W = F * d
F = A * p
substituting,
W = A * p * d
but:
V = area * height
dV = A * d
W = p * dV > PV work for constant pressure process
2. isothermal conditions: T = c
W = S(V1 V2) p * dV
but:
pV = RT
and
p = RT/V
substituting,
W = S(V1 V2) p * dV
W = S(V1 V2) RT/V * dV
because temperature T = constant,
W = RT * S(V1 V2) 1/V * dV
but the
Integral of 1/v * dv = ln V
putting the limits (V1 V2)
W = RT * (ln V2  ln V1)
but from logarithmic properties
ln (u/v) = ln u  ln v
ln (uv) = ln u + ln v
ln u^n = n ln u
finally getting
W = RT * ln (V2/V1) > PV work for constant temperature process
where:
W = Work done by compression or expansion( if done on the surroundings)
F = Force
d = distance
p = absolute pressure
A = area
V = volume
dV = change in volume
T = absolute temperature
V2 = volume at point2
V1 = volume at point1
R = gas constant
S(V1 V2) = integral from V1 to V2
CHEMICAL ENGINEERING: Chemistry  Molecular weight, molar mass, molecular mass, moles, Avogadro's number, molecules
Molecular Weight (also called molecular mass or molar mass)
 is the sum of the atomic weights of all the atoms in a molecule.
 it has a unit of amu. One atomic mass unit (1 amu) is 1/12 the mass of the carbon12 isotope, which is assigned the value 12.
water: H2O
1 molecule of water H2O = 2 atoms of hydrogen + 1 atom of oxygen
components:
2 H * 1 amu = 2 amu
1 O * 16 amu = 16 amu
MW of water = sum of components
MW of water = 2 amu + 16 amu
MW of water = 18 amu
dry air:
MW of air = 29 amu
Moles
A mole (mol) of any substance is the amount of that substance that contains Avogadro's number of atoms or molecules. Avogadro's number is defined as the number of carbon atoms in 12 g of 12C. It has a value of 6.022 x10^23 molecules/mol.
A mole of a substance is Avogadro's number of that substance.
n = N/Na
n = m/MW
m = n * MW
where:
n = number of moles
m = mass of substance
MW = molecular weight of substance
N = number of molecules
Na = Avogadro's Number, 6.022 x10^23 molecules/mol
Avogadro's Number
 the number of atoms needed such that the number of grams of a substance equals the atomic mass of the substance, 6.022 x10^23 /mol
 an Avogadro's number of substance is called a mole.
 for example, a mole of carbon12 atoms is 12 grams, a mole of hydrogen atoms is 1 gram, a mole of hydrogen molecules is 2 grams
Units of molar mass > g/mol
The most common unit of molar mass is g/mol because in that unit the numerical value equals the average molecular mass in units of u.
1 mole of Water H2O
average atomic mass of Hydrogen = 1 u
average atomic mass of Oxygen = 16 u
molecular mass of water = (2 * 1 u) + 16 u = 18 u
Thus,
1 mole of water has a mass of 18 grams.
Problem 1:
Ten kg of Carbon dioxide has a volume of 998 L at a pressure of 200 kPa. Determine the number of moles of CO2 present.
find:
n = number of moles of CO2
given:
m = 10 kg = 10,000 g
solution:
Mw of CO2 = 12 + 2*16
MW of CO2 = 12 + 32
MW of CO2 = 44 g/mol
n = m/MW
n = 10,000 g/44 g/mol
n = 227.3 mol
Problem 2:
How many molecules are present in 5 moles of H2O?
find:
N = number of molecules
given:
n = 5 moles
solution:
n = N/Na
5 = N/6.022 x10^23
N = 5 * 6.022 x10^23
N = 30 x10^23
N = 3.0 x10^24 molecules
MECHANICAL ENGINEERING: Thermodynamics  Closed system, pistoncylinder, Boyle's law, Constant Temperature, Parabolic curve
CLOSED SYSTEM: pistoncylinder
conditions:
Temperature is constant, T = c
Boyle's law: Absolute pressure is inversely proportional to the volume of a gas
pV = constant
pV = k
p1V1 = p2V2
curve: Parabolic
where:
p = pressure of the gas. p1, p2 are the pressures of the gas at points 1, 2
V = Volume of the gas. V1, V2 are the volumes of the gas at points 1, 2
k = constant
1. A certain gas in a piston is compressed to a volume of 12 L. Its original volume was 21 L at 10 bar. Find the new pressure if the temperature remains constant.
find:
p2 = pressure corresponding to the compressed volume
given:
V2 = 12 L
V1 = 21 L
p1 = 10 bar
solution:
p1V1 = p2V2
10 * 21 = p2 * 12
p2 = 210/12
p2 = 17.5 bar
MECHANICAL ENGINEERING: Thermodynamics  Atmospheric, Barometric, Gage, Absolute, and Vacuum pressure
Atmospheric pressure > Patm
= 14.7 psi
= 101.325 kPa
= 760 mmHg
= 760 torr
= 29.92 inHg
= 1013.25 millibars
= 1.01325 bar
When gage pressure is above atmospheric:
Pabs = Patm + Pgage
When gage pressure is below atmospheric (vacuum):
Pabs = Patm  Pgage
where:
Pabs = absolute pressure
Pgage = gage pressure
Patm = atmospheric pressure
1. An oxygen cylinder has a pressure of 2400 psig at 70 F. What is the absolute pressure of the oxygen inside?
find:
Pabs = absolute pressure of oxygen inside the cylinder
given:
Pgage = 2400 psig
solution:
gage pressure is above atmospheric:
Pabs = Patm + Pgage
Pabs = 2400 + 14.7
Pabs = 2414.7 psia
2. The gauge at the vacuum pump reads 7 in. of Hg. What is the absolute pressure?
find:
Pabs = absolute pressure at the vacuum pump
given:
Pgage = 7 inHg
solution:
gage pressure is below atmospheric (vacuum):
Pabs = Patm  Pgage
Pabs = 29.92  7
Pabs = 22.92 inHg
Thursday, November 8, 2012
MECHANICAL ENGINEERING: Pump work  work done by a pump in lifting a fluid
Wp = F * h
where:
Wp = pump work, the work done by the pump
F = weight of fluid
h = lifting height, measured from the centroid
1. Find the work needed to pump all the water in an 8ft radius hemispherical tank to a height of 10 ft above the top of the tank.
find:
Wp = pump work
given:
Hemispherical tank (Centroid: y = 3/8 r)
D = Water Density = 62.4 lb/cu.ft
r = 8 ft
h1 = 10 ft
solution:
V = 2/3 pi * r^3
V = 2/3 * 3.14 * 8^3
V = 1072 cu.ft
F = D * V
F = 62.4 * 1072
F = 66,893 lb
h = h1 + yCentroid
h = 10 + 3/8 r
h = 10 + 3/8 (8)
h = 10 + 3
h = 13 ft
Wp = F * h
Wp = 66,893 * 13
Wp = 869,609 lb.ft
Thermodynamics  Specific heats at constant pressure, volume, Specific heat ratio, Gas constants
Specific heat
The ratio of the amount of heat required to raise the temperature of a unit mass of a substance by one unit of temperature to the amount of heat required to raise the temperature of a similar mass of a reference material, usually water, by the same amount.
Specific heat ratio
The specific heat ratio of a gas is the ratio of the specific heat at constant pressure, Cp, to the specific heat at constant volume, Cv. It is sometimes referred to as the adiabatic index or the heat capacity ratio or the isentropic expansion factor or the adiabatic exponent or the isentropic exponent.
For an ideal gas, the heat capacity is constant with temperature.
k = Enthalpy/Internal energy
k = H/U
Enthalpy
H = Cp * T
Internal energy
U = Cv * T
Specific heat ratio (k)
k = H/U
k = Cp * T/CV * T
k = Cp/Cv
Specific heat and Gas constant R
Cp = Cv + R
R = Cp  Cv
Derivation
Heating a gas at constant pressure increases the internal energy of the gas and Work is done, whereas supplying the same amount of heat at constant volume only increases the internal energy, no work is done.
constant pressure process:
du = dq  w
dq = du + w
w = pdV
dq = du + pdV
from ideal gas relations
pV = mRT
but at constant pressure
pdV = mRdT
thus
dq = du + mRdT > equation1
and
dq = m * cp * dT
equation1 becomes
m * cp * dT = du + mRdT > equation2
constant volume process:
du = dq  w
at constant volume, w = 0
w = pdV
w = p(v2  v1)
but v2 = v1
w = p(0)
w = 0
du = dq + 0
du = dq
dq = m * Cv * dT
du = m * Cv * dT > equation3
equation3 in equation2
m * cp * dT = du + mRdT
m * cp * dT = (m * Cv * dT) + mRdT
factoring
(m * dT) (Cp) = (m * dT) (Cv + R)
(m * dT) cancels and thus leaving
Cp = Cv + R
Saturday, November 3, 2012
MECHANICAL ENGINEERING: Springs  connected in series, parallel
Hooke's law on springs:
Stretch is directly proportional to the Force
F = k S
where:
F = force applied
k = spring constant
S = stretch of spring
Springs connected in series



wwws1wwws2wwws3> F



S = s1 + s2 + s3
where:
S = total stretch of spring, equal to the sum of individual stretches of each spring s1, s2, s3
F = force applied
Springs connected in parallel



wwwwk1f1
wwwwk2f2> F
wwwwk3f3



if the springs are connected by a rigid bar, then
S = s1 = s2 = s3
sum of forces along x = 0; then
F = f1 + f2 + f3
f1 = k1 * s1
where:
k1, k2, k3 = spring constants
S = total stretch of spring, equal to the sum of invidual stretches of each spring s1, s2, s3
F = force applied, equal to the individual forces on each springs
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