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Jahnavi Raman Period 1 semester 2 (thermo (calculating heat energy…
Jahnavi Raman Period 1 semester 2
empirical
lowest whole number ratio of atoms in a compound
percent to mass 2. mass to mole 3. divide by small 4. multiply till whole
molecular formula
true number of atoms of each element in a formula of a compound
ionic compound formulas are always empirical
combustion analysis
used when elements making up a substance are carbon, hydrogen, oxygen, and sometimes nitrogen
determine mass of each element present in original compound (ex. carbon in CO2, hydrogen in H2O, and sometimes nitrogen in compounds such as NH, N2, N, NO2, etc)
mass to mole 3. divide by small 4. multiply till whole
gas
nature of gases
they expand to fill their containers 2. they are fluid-they flow 3. they have a low density (1/1000 the density of the equivalent liquid or solid) 4. gases are compressible 5. gases effuse and diffuse
pressure
caused by collisions of molecules with the walls of a container, equal to force/unit area, SI units: Newton/meter squared = Pascal (Pa)
laws
Boyle's law
pressure is inversely proportional to volume when temperature is held constant: P1V1=P2V2
Charles' Law
volume and temperature have a direct relationship: V1/T1 = V2/T2
Gay Lussac's Law
pressure and temperature have a direct relationship: P1/T1 = P2/T2
Avogadro's law
volume is directly proportional to the number of moles in a gas: V1/n1 = V2/n2
Dalton's law of partial pressures
Ptotal = P1 + P2 + P3 + ...
ideal gas law
PV = nRT, where R is a gas constant (0.08206 for atm, 8.314 for KPa, and 62.4 for torr
density: D = MP/RT
combined gas law: P1V1/T1 = P2V2/T2
STP
standard temperature pressure
Pressure: 1 atm, 760 torr, 101.325 KPa
temperature: 273 Kelvin
molar volume: 22.42 L
gas behavior
ideal gases- kinetic molecular theory
imaginary gases fitting all assumptions: collisions are elastic, gases have tiny particles far away frm each other, no kinetic energy lost, no force of attraction between particles
real gases experience intermolecular attractions, have volume, and don't have elastic collisions, gases likely to behave ideally have high temp and low pressure in addition to small nonpolar gas molecules
gas stoich: if reactants and products are @ same conditions, mole ratios of gases are also volume ratios
thermo
calculating heat energy absorbed or released: q = mcΔT
joule is the basic unit for measuring heat
calorie: heat required to raise temperature of 1 g of water by 1 degree C
kinetic energy: energy of motion
enthalpy: amt of heat energy released/absorbed during a process
specific heat: amt of heat required to raise temperature of base unit of a substance by 1 degrees C
calorimetry: amt of heat absorbed/released during physical/chemical change can be measured, usually by the change in temp of known quantity of water in calorimeter
phase diagram: represents phases as a function of temperature and pressure
solutions
homogenous mixtures
water is the universal solvent, but it can also be a solute
saturation
saturated solution: maximum amount of solute dissolved
unsaturated solution: less than maximum amt of solute dissolved
supersaturated solution: more than the maximum amt of solute is dissolved
calculations
mass percent/composition: ratio of mass units of solute to mass units of solution, expressed as a percent
(mass of solute/mass of solution) x 100
parts per million/billion (ppm/ppb): of parts of solute to 1 million parts of solutions, usually applied to very dilute solutions with very low concentrations
(mass of solute/mass of solution) x 1,000,000
grams/liter: expresses solubility, ratio of mass units of solute/volume of solution (L)
(mass of solute/volume of solution)
mole fraction: ratio of moles of solute to total moles of solution Xa=(n a/n a + n b)
molarity: ratio of moles of solute to L of solution mol/L = M = (moles of solute/liters of solution)
kinetics
chemical kinetics is the area of chemistry that concerns reaction rates
collision model
the key idea is that molecules must collide to react. however, only a small fraction of collisions produces a reaction
this is because collisions must have sufficient energy to produce the reaction (must equal/exceed activation energy)
colliding particles must be correctly oriented to one another in order to produce a reaction
rate laws
differential rate laws that express or reveal the relationship between the concentration of reactants and the rate of reaction
factors affecting rate
increasing temperature: always increases the rate of a reaction
particles collide more frequently
particles collide more energetically
increasing surface area: increases the rate of a reaction by increasing collisions
increasing concentration: usually increases the rate of a reaction
particles collide more frequently
presence of catalysts: they lower the activation energy by providing alternate pathways
reaction rate
change in concentration of a reactant of product per unit of time
rate = ([A] at time t2 - [A] at time t1 / t2-t1)
equilibrium
chemical equilibrium is when the rate of the forward reaction equals the rate of the reverse reaction and the concentration of products and reactants remains unchanged
LeChatelier's principle
reversible reactions are chemical reactions where the products can react to re-form the reactants
law of mass action
equilibrium expression which looks like this K=[C]^l [D]^m / [A]^j [B]^k
equilibrium expression for a reaction is the reciprocal for a reaction written in reverse
product favored equilibrium
large values for K signifies that the reaction is "product favored", in other words, the system shifts to the right. when equilibrium is achieved, most of the reactant have been converted into product
reactant favored equilibrium
small values K signifies that the reaction is "reactant favored", n other words, the system shifts to the left.
reaction quotient is Q, equilibrium constant is K
if Q > K, the system shifts to the left, consuming products
if Q < K, the system shifts to the right, consuming reactants
acids and bases
reactions
neutralization
acid base neutralization reactions produce a salt and water
conjugate acid forms when base gains a proton, conjugate base forms when acid loses a proton
dissociation
either dissociates with or without water as a reactant
strong acids dissociate completely, weak acids dissociate slightly, so ICE tables are required to find concentration at equilibrium and pH
properties/facts
acids
low pH, conduct electricity, sour, juices and fruits, common as aqueous and liquids
to find pH: -log[H3O+] to find pOH: -log[OH-]
bases
bitter, slippery, cleaning products, high pH
models
arrhenius
acids produce hydrogen ions, while bases produce hydroxide ions
bronsted-lowry
acids are proton donors while bases are proton acceptors
lewis acid model
acids are electron acceptors while bases are electron donors