what are the units for enthalpy?
kJ per mol
how can enthalpy be calculated in terms of charge and moles?
delta H = -Q/n
what are the assumptions made for water based calorimetry?
rate of reaction is fast enough that max temp occurs before misture begins to cool to room temp, no heat is lost to surroundings, the solution is dilute enough that its density and specific heat capacity are equal to water
what are sources of error for combustion calorimetry?
incomplete combustion, heat absorbed by draught shield, heat lost to surroundings
why is breaking bonds an endothermic process?
because the attractive force between shared pair of electrons and nuclei of the two atoms must be overcome, which requires energy
what is bond enthalpy?
the energy required to break one mole of a bond in the gaseous state under standard conditions
how can the change in enthalpy of a reaction be calculated using bond enthalpies?
using the data booklet, break the bonds one at a time and sum up their bond enthalpies for each step
why would calculated change in enthalpy using bond enthalpies be different compared to the actual change in enthalpy?
because some of the states may not be gaseous, databooklet uses averages as same bond types can have different bond enthalpies
why is making bonds an exothermic process?
because energy is released
how can the enthalpy of the overall reaction be calculated through tracking the breaking and forming of bonds?
change in enthalpy equals the sum of the bonds broken (reactants) - the sum of the bonds formed (products)
what is hess’s law?
the value for any change in enthalpy of a reaction that can be written in steps equals the sum of the change in enthalpies for all steps
for enthalpies of combustion, what is the relation between reactants, products, and the middle step?
the reactants and products can form the combustion products (arrows from reactants and products to middle step)
for enthalpes of formation, what is the relation between the reactants, products, and the middle step?
both the reactants and the products can be produced form the elements in standar state (arrows from middle step to reactants and products)
what is the enthalpy of formation for an element in its standard state?
zero
what is the difference between calculating change in enthalpy of combustion vs formation?
combustion: reactants minus products
formation is products minus reactants
what are the results of the combustion of organic compounds?
CO2, water and release of energy
is ionization energy poitive (enothermic) or negative (exothermic)?
positive/endothermic
is electron affinity positive (endothermic) or negative (exothermic)?
negative/exothermic
why is the second electron affinity positive/endothermic?
because it must overcome the repulsion between the negative anion (after first electron was gained) and the negative electron
what is enthalpy of atomization?
the energy exchange when one mole of gaseous atoms of the elements are formed from the element in its standard state
for diatomics, what value must be used to produce one mole of the atom alone?
half of the bond enthalpy for the two atoms bonded together
what is the change in enthalpy of atomization for noble gases?
zero
why will the change in enthalpy of atomization always be positive?
because it is the breaking of bonds to create individual gaseous atoms
how can the change in enthalpy of the reaction to turn the metal and non-metal in their gaseous states into the metal cation and non-metal anion be calculated?
by finding the sum of the ionization energy for the metal into metal cation and the electron affinity for the non-metal into non-metal anion
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1.1.2 - The Kinetic Molecular Theory19
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1.1.3 - Kinetic Energy and Temperature8
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1.2.1 - The Atomic Model13
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1.2.2 and 1.2.3 - Isotopes and Mass Spectra14
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1.3.1 and 1.3.2 - Emission Spectra22
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1.3.3, 1.3.4 and 1.3.5 - Electron Configuration26
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1.3.6 and 1.3.7 - Ionization Energies13
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Unit 2: Periodic Table Trends115
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2.1 - The Ionic Model17
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2.2.1 - 2.2.2 - Covalent Bonding, Octet Rule, Lewis Formulas14
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2.2.3 - Coordination Bonds2
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2.2.4 - VSEPR Theory24
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2.2.13 - Expanded Octets14
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2.2.5-2.2.6 - Bond Polarity and Molecule Polarity6
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2.2.8-2.2.9 - Intermolecular Forces24
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2.2.10 - Chromatography15
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2.2.7 - Covalent Network Structures18
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2.2.11-2.2.12 - Resonance Structures and Benzene17
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2.2.14 - Formal Charge7
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2.2.15 - Sigma and Pi Bonding14
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2.2.16 - Hybridization22
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2.3 - The Metallic Model11
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1.4.2-1.4.3 - Relative Atomic Mass, Formula Mass, and Molar Mass5
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1.4.4 - Empirical and Molecular Formulas10
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1.4.5 - Molar Concentration7
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1.4.6 - Avogadro's Law7
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1.5 - Ideal Gases19
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2.1 - Reactivity8
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UNIT 5 - Energetics and Thermochemistry - Reactivity 1.1 - 1.461
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Chem40
