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# Chem Exam 1.docx

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School
Department
Chemistry
Course
01:160:161
Professor
Siegel
Semester
Fall

Description
Chem Exam 1 Ch.1 Homogeneous: the composition of the mixture is uniform throughout Ex: salt water, diet cola Heterogeneous: composition of the mixture is not uniform. Separable Ex: concrete, milkshake • Separation of mixtures: o Filtration: separate heterogeneous mixtures of liquid/solid o Distillation: separates liquids with different boiling points Physical change: the identity of the matter has not changed. Reversible, separable Ex: melted ice, ice forming Chemical change: the original substance no longer exists. Irreversible. Ex: burnt leaves, baked cookies Extensive Properties: value of a substance based on its mass (mass/volume/length) Intensive Properties: value of substance does not depend on the amount of matter (density/temperature) TGM-KDC-MμNP  12, 9, 6, 3, -1, -2, -3, -6, -9, -12 Exact numbers: numbers with defined values, obtained by counting Ex: 1 dozen=12 items, there are 12 people in a room Inexact numbers: numbers found other than counting, such as measuring Significant Figures: • Zeros to left of nonzero digit are not significant • Zeros to the right of nonzero digits are significant ONLY if there is a decimal • Addition/subtraction: lowest number of digits to the right of the decimal point • Multiplication/division: lowest number of digits in original numbers **Don’t round until final solution! Accuracy: how close to a true value Precision: how close a series of replicate measurements are to one another Pressure= Pascal/torr/atm Temperature: K= °C + 273.15 °F = (9°F/5°F)(temp in °C) + 32 °F General conversions: A°(angstrum=1x10^-10m) 1g/cm^3 = 1g/mL = 1000 kg/m^3 1g/L = 0.001g/mL L=dm^3 mL = cm^3 d=m/v Ch.2 Cathode ray: metal plates connected to high voltage source. Negative charged plate emits radiation (cathode rays), which then moves to positive plate. When pass through hole, produced bright light. The composition of the cathode does not affect the property of the cathode rays Coulomb’s Law: like charges repel-- opposite charges attract one another Radioactivity: Bacquerel • Alpha rays (α): (+) charge; deflect away from plate • Beta rays (β): electrons with (-) charge; deflect away form (-) plate • Gamma rays (ϒ): no charge Atomic Models: Rutherford- disproved Raisin Pudding Model. Found that all positive charge of atom is concentrated at center of atom • Nucleus: positive center that contains all mass of the atom containing the protons and neutrons • Electrons are dispersed around the nucleus • The atom itself is neutral when protons=electrons Atomic number= number of protons Mass number = Protons + Neutrons Isotopes: different number of neutrons (same atomic #)= different mass number A mass # (protons + neutrons) X Z  atomic # (# of protons) AverageAtomic Mass: weighted average of masses of naturally occurring isotopes [amu x (natural abundance %)] + [amu x (natural abundance %)] = amu The Mole: Avogadro’s number (NA): 6.022 x 10^23 mol-1 Molar Mass: mass of 1 mole in grams Ex: 1molCa = 40.08g/mol Divide by molar mass Divide by NA g/(g/mol) = mol atoms x1mol/(6.022x10^23) = mol -------------------------- ----------------------------- Grams Moles Atoms ------------------------- ----------------------------- Multiply by molar mass Multiply by NA Mol x (g/mol) = g mol x (6.022x10^23atoms / 1mol) = atoms Ch.3 Kinetic Energy- energy of motion EK = ½ mu^2  (m = mass of object) & (u = velocity of objects) • Thermal energy: random motion of atoms or molecules Potential energy: energy possessed by an object by virtue of its position • Chemical energy: energy stored within structural units of chemical substances • Electrostatic energy: energy that results form interaction of charged particles • Opposite charges attraction ……. Like charges  repulsion E el= c(Q 1Q 2/d) Properties of waves: C = λ/ν (λ=length of wave (m)), (ν=frequency of waves(s^-1) C=3.00x10^8m/s  speed of light through a vacuum (constant) Quantization of energy: (a quantum-Planck). E = h ν the energy of a photon = a quantum • Photon- stream of light particles • h: planck’s constant = 6.626x10^-s J • v: frequency of light Binding Energy: hν = KE + w (kinetic energy of ejected electron), (w=binding energy of electron) General Conversion: 1J= 1N*m 1N= kg*m/s^2 1kg=1000J Line Spectrum: when an energized H atom emits radiation, the electron drops from higher-energy orbit to a lower one giving up a quantum of energy (photon) of light E n = B / n^2 • B=-2.18x10^-18J • (-) represents the atom is lower than the energy of free electron As electron gets closer to the nucleus,ngets larger (more negative) Ground State: the lowest energy of an atom • When n=1 Excited State: higher in energy • When n>1 • the higher the excited state, the farther away the electron is from the nucleus Radius of each orbit= n^2 the larger n gets, the larger the radius  Radiant energy absorbed: ground state  excited state  Radiant energy emitted: excited state (higher energy)  ground state (lower energy) Change in energy: ΔE = B ((1/n i^2) – (1/n f^2)  Remember:ΔE = hc/ λ Change in state (n=initial state),f= final state) Waves: • Waves can behave like particles λ = h/mu  the wavelike property of the wavelength= the mass and Velocity of the particles • The bigger the particle, the smaller the wavelength Quantum Mechanics: Heisenberg Uncertainty Principle: it is impossible to know simultaneously both the momentum and position of a particle with certainty Δx x mΔu ≥ h/4π • X: position of a particle • U: velocity This principle applied to the H atom proves that the electron does not orbit the nucleus in a defined path Quantum numbers: describe the distribution of electron density in an atom Principle quantum number: (n) – designate the size of the orbital • Also referred to as a shell • As n increases, energy and size increase as well Angular Momentum Quantum Number: (ι) – describes shape of the orbital This number depends on n: the possible values of ι= 0n-1 L=0 s  n=1 L=1 p  n=2 possible values: 0(2-1)=1 L=2 d  n=3 possible values: 0(3-1)=2 L=3 f  n=4 possible values: 0(4-1)=3 • Can be referred to as a subshell • the number of possible l values is equal the value of n* Ex: 2s  2 is the shell (n value) and s is the subshell (l value) Magnetic Quantum Number (mι) - orientation of orbital in space • Depends on the value of ι: (2ι + 1)  -ι…0…ι *Number of subshells= n *Number of orbitals= n^2 Electron Spin Quantum Number (m ): spin of electron in orbital • Describes the electron that occupies the orbital • Possible values: +1/2, -1/2 Electron Configuration: • The energy of an orbital in a many-electron system depends on both the value of n and the value of l Paulie’s Exclusion Principle: no two electrons can have the same set of 4 quantum numbers (n,
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