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Chemistry 141 Exam -2 Questions And Answers Rated A+ New Update Assured Satisfaction
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Chemistry 141 Exam #2- ANS-waves
- ANS-What are the metric conversion factors?
- ANS-What does the stoichiometry map look like?
__FeCl3 + 3NaOH----->__Fe(OH)3 + 3NaCl - ANS-Balance the following equation: __FeCl3 +
__NaOH------>__Fe(OH)3 + __NaCl
- 13.8 Billion years ago - singularity
- 1 picosecond after - no atoms - only leptons (quarks, electrons)
- 1 microsecond - protons and neutrons
- Few minutes - H+ D+ He2+ Li3+ (density of air)
- For 400K years temp dropped - no further fusion
A billion years later:
• Clumping (universe is not homogeneous)
• Gravitational attraction-raised temperature
• Fusion restarted
• Starsformed
• Hydrogen burning
- 4 1H+ -> 4He2+ + 2e+ + energy
• Helium burning
- 3 4He2+ -> 12C6+ + (lots of) energy - ANS-Describe the Big Bang Theory
- Describes the spin of the electron in the orbital
- ms can have values of +1⁄2 or -1⁄2.
ms describes the spin of the electron in each orbital.
- You can only have two electrons in every orbital!
- One has ms = +1⁄2 and one has ms = -1⁄2. - ANS-What does the Spin Quantum Number (ms)?
- Determines the energy of the orbital and identifies its
shell
- The larger the number, the higher the energy and the larger the orbital. - ANS-What does the
Principle Quantum number (n) represent?
- Identifies the type of orbital (s,p,d,f,...) and subshell - ANS-What does the Angular Momentum
Quantum Number (l) represent?
- Specifies a particular orbital within a subshell (ie the
,orientation of the orbital) - ANS-What does the Magnetic Quantum Number (M1) represent?
[He] 2s2 2p3
A. 2 core, 5 valence - ANS-How many core electrons & valence electrons does N have?
A. 2 core, 5 valence
B. 5 core, 2 valence
C. 4 core, 3 valence
#1: 10 M
#2: 100M
#3: 1000M - ANS-• Lets say we have 2 objects 1m apart (100 m)...
• How far apart would 2 objects be that were 101 m apart?
• How far apart would 2 objects be that were 102 m apart?
• How far apart would 2 objects be that were 103 m apart?
• But caused by the same phenomenon - the effective nuclear charge - ANS-What are atomic
radius and ionization caused by?
• Each energy level has a
quantum number
• The higher the number the higher the energy
• Energy levels are NOT ORBITS
• Electrons transition between energy levels by absorbing or emitting photons
• Energy of absorbed/emitted photon is equal to the energy difference between energy levels
• Only shows energy not distance - ANS-Describe Energy Diagrams
• Einstein postulated that light must come in packets (or particles or quanta) - called photons.
• The energies of photons have certain values (quantized). - ANS-What are photons?
• Electrons circling the nucleus like planets around the sun.
• Would have led to the atom blowing up! (charges circling in an electric field would decay)
• This model was not sustainable. - ANS-Why was Rutherford's model incorrect?
• Energy - increases as frequency increases (and wavelength decreases)
• Directly proportional - ANS-How are frequency and energy related?
• Energy is transferred as a particle (photon) that has a definable energy.
• E =h v
• One photon ejects one
electron
,• If the photon does not have enough energy - then no electron is ejected
• Einstein - photoelectric effect - does not depend on the intensity - just the frequency (energy) -
ANS-How does photo electric effect prove light is a particle?
• Fusion (adding two nuclei together)
• Fission (breaking apart)
• Radioactive Decay (emitting particles, α, β, γ etc) - ANS-What are the three types of nuclear
reactions?
• Increasing intensity does not result in more energy. Amplitude only results in more photons
being released, not energy.
•Analogy: Vending machine
• To eject one electron, it takes one high energy photon. You can't use multiple high energy
electrons. - ANS-What are the main points of the photoelectric effect?
• Involve nucleus (not electrons)
• Often result in change in element (since element is defined by the number of protons) -
ANS-Describe Nuclear Reactions
• Involve rearrangements (sharing, donating or accepting) of valence electrons
• The element undergoing a chemical reaction does not change (EVER)
• Don't involve the nucleus. - ANS-Describe Chemical reactions
• Just a number! - A big number...
• 6.022 x 1023 "things" - ANS-What is a mole?
• London dispersion forces and covalent bonds have similar causes (electrostatic attraction of
the electrons of one atom to the nucleus of another).
• The differences are in:
- the magnitude of the attraction and
- how the electrons are arranged in the new species (which is formed by the interaction). -
ANS-Why the difference in strength between LDFS and Covalents?
• Macroscopic objects - λ is much smaller than the object - no affect on properties
• Electrons - λ about the size of atom - affects
properties - ANS-Does the wavelength of macroscopic/electrons affect them?
• Many metals emit electrons when electromagnetic radiation shines on the surface.
, • The light is transferring energy to the electrons at the metal surface - where it is transformed
into kinetic energy that give the electrons enough energy to "leave" the atoms in the metal
• Uses - photomultipliers, photocells, garage door openers
• Provides evidence for light as a particle - ANS-Describe the photoelectric effect
• Nuclear Fission is the fragmentation of heavy nuclei to form lighter, more stable ones.
• Neutrons released in the fission of 235U can induce three more fissions, then nine, and so on
leading to a chain reaction.
• Critical mass is the mass required for the chain reaction to become self-sustaining. -
ANS-What is fission?
• Nuclear reactions are accompanied by changes in mass!
- (UNLIKE chemical reactions)
• The mass is converted into energy (mass-
energy equivalence): E = mc2
• E is the "binding energy" (the energy released when mass is converted to energy). -
ANS-Describe nucleus reactions and energy changes
• Nucleus emits or captures particles or energy in the form of electromagnetic radiation.
• Common types
Alpha particle emission - α or 42He2+
Beta particle (electron) emission - β or 0-1e or e+ Positron emission - β+ or 01e
Electron capture
γ electromagnetic radiation - ANS-What is radioactive decay?
• Originally developed by Mendeleev
• On basis of experimental behavior and repeating (periodic) patterns)
• He left spaces for undiscovered elements
• Originally on basis of increasing atomic mass - then on atomic number
• Really electron organization explains repeating patterns - ANS-Describe Periodic Table History
• Planck modeled the energy of a photon
• E = h v (h= 6.626 x 10-34 J.s)
• EM radiation comes as packets of energy - quantized - ANS-What equation is used to
determine the energy of a photon?
• Schrödinger - by treating electrons as waves derived by mathematical descriptions of the
energies and probabilities of electrons.
- The equation is called a wave equation and the description of an electron is called a wave
function Y (psi).
- The probability of finding an electron is Y2.
• We'll use the results of quantum calculations, not the calculations themselves!
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