Chem 1465 1st EditionExam # 2 Study Guide Lectures: 7 - 9Lecture 7 (February 12)-5 properties of gases:- Expand to fill the volume of any container- Must lower density then solids or liquids- Higher variable density- depends on conditions- Mix with one another thoroughly - Change in volume is dramatic with change in temperature- Boyle’s law: occurs under constant temperature conditions, pressure is inversely proportional to volume. At a constant temperature P1V1=P2V2 or PiVi=PfVf- Charles’ law: occurs under constant pressure, volume is proportional to temperature. At constant pressure ViTi=VfTf where temperature is in kelvin- Avogadro’s law: equal volumes of gases at the same temperature and pressire contain equal numbers of particles (could be atoms or molecules). At constant temperature and pressure, volume is proportional to number of moles- Molar volume of a gas at STP is 22.4 moles. (22.4 liters of gas to 1 mole)- Ideal gas law: PV=nRT where n is number of moles and R=0.08206- Dalton’s law (partial pressure): for a mixture of gases, the total pressure exerted by the gases is the sum of the individual partial pressures. Expressed like PA= XAPtot where XA is NA/Ntot- 5 postulates for kinetic theory of gases:- Gases consist of individual particles in constant random motion- Volume of gas particles is extremely small compared to the volume of the container- Collisions between gas particles are elastic - Attractions between gas particles are extremely weak and negligible - The average kinetic energy of gas particles is going to depend only on temperature and directly proportional to temperature Lecture 8 (February 19) -Formulas and important values- h is plank’s constant = 6.626x10-34 J/sec- c is the speed of light = 2.998x108 m/sec- λν = c- Ephoton = hλ & Ephoton = hc/ λ- λ = h/ mv- En = -2.18x10-8 J x (1/n2)- The photoelectric effect: when light shines on a surface die to electrons being emitted. Classical theory would predict that changing the wavelength or light intensity would affect the emissions of electrons. So a dim light should result in a time lag to allow enough energy to be transferred to dislodge an electron. - Einstein proposed that a beam of light behaves as if it were composed of a string of small particles or packets of energy called photons or quanta. The energy of a photon dependsonly on frequency and not on amplitude or brightness. The intensity of light correspondsto the number of photons not the energy of the photons. Main conclusion: in addition tobehaving as waves, light also behaves as particles; energy is quantized, meaning it exists only in discrete amounts. - Atomic spectra: the light given off by an excited hydrogen atom is not a continuous spectrum, but rather a line spectrum. - En = -2.18x10-18 J (1/n2) where En is the energy of a hydrogen electron at the nth energy level.- ΔE = Ef – Ei- ΔE = -2.18x10-18 J(1/nf2 – 1/ni2)- Wave like properties: De Brogile proposed that if energy is particle like then perhaps matter is wave like. - Since Ephoton= hv and E= mc2- Substitute hv=mc2 so λ=h/mc- For a particle traveling at velocity v: λ=h/mvLecture 9 (February 26)-Quantum mechanics- Quantum mechanics treats electrons differently. Quantum mechanics says that an electron has both particle like and wave like properties- Schrodinger’s equation: Hψ=Eψ where H is Hamiltonian operator, ψ is wave function, and E is energy- The physical meaning of ψ is probability density- the probability of finding an electron in a given volume in space-Quantum numberletter designation Name What is describes Possible valuesn Principal QN Shell of electron 1,2,3,4…l Angular momentum QNShape of orbitalL=0 is s orbitalL=1 is p orbitalL=2 is d orbitalL=3 is f orbital 0,1,2,3MlMagnetic QN Orientation -L to +LMsSpin QN Spin of electron -1/2 or +1/2-Rules for determining ground state electron configuration- Aufbau procedure: start with lowest energy orbital and fill up from there- Pauli Exclusion Principle: no two electrons in an atom can have the same 4 quantum numbers. You can have a maximum of 2 electrons per orbital as long asthey have opposite spins- Hund’s rule: when filling degenerate orbital (orbitals that are equal in energy) electrons always occupy singly with parallel spin before paired. (remember: parallel before paired- Remember that there is a special stability associated with filled outer most shellsand half-filled subshells-Atomic and ionic radii- Atomic size decreases from left to right across the periodic table because we are increasing nuclear charge. Size increases going down the periodic table.- Ionic size: cations are always smaller than parent ion and anions are always bigger than parent