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Chemical Bonds and Thermochemistry

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  • In an exothermic reaction, the temperature of the surroundings increases because the molecules in the surrounding have
    a greater kinetic energy
    a lower kinetic energy
    a greater potential energy
    a lower potential energy
  • Which series shows the correct order of metallic bond strength from strongest to weakest?
    Na > K > Rb > Mg
    Rb > K > Na > Mg
    Mg > Na > K > Rb
    Mg > Rb > K > Na
  • Which molecule is most polar?
    CCl 4
    CHF 3
    CF 4
    CClF 3
  • What is the overall charge of the compound sodium chloride?
    0
  • Refers to a chemical reaction or physical change in which heat is absorbed. That is, the system gains heat; q is positive.
    endothermic
  • Which of the following is a state function?
    temperature
    heat
    force
    work
  • What would be the best use of graphite?
    lubricant because it is soft and slippery with weak forces
    decorative stone for rings
    electrode
    used in drill heads
  • What is the electron and molecular geometry for carbon dioxide. From this data, is it polar?
    Electron: linear. Molecular: linear. - It is symmetric therefor NOT POLAR
  • A chemical system in which neither energy nor matter can flow into or out of a system is described as
    a closed system
    a chemical system
    an open system
    an isolated system
  • What energy changes occur when chemical bonds are broken?
    It depends on the type of bond
    Energy is absorbed when they are broken
    Energy is released when they are broken
    it depends on the state of matter
  • Which change of state is exothermic?
    CO2(s) → CO2(g)
    NH3(g) → NH3(l)
    H2O(l) → H2O(g)
    Fe(s) → Fe(l)
  • a property of a substance that is independent of the amount of the substance present.
    intensive (e.g. mp, bp, density)
  • Why do ionic solids NOT conduct electricity?
    This is due to the fact that ions are not free to move in a solid as they are arranged in an ionic lattice.
  • What is the arrangement of the bonds in diamond as shown in this structure?
    tetrahedral - (4 bonds each 109.5 degrees apart)
  • Covalent compounds are formed when atoms
    share valence electrons
  • Which of the following would you expect to have the highest melting point?
    hydrogen chloride
    magnesium fluoride
    phosphorous trichloride
    dinitrogen oxide
  • What is the chemical formula for calcium oxide?
    CaO
  • What will the result be when a reaction between bismuth and fluorine takes place?
    BiF3
  • Best explanation here that graphite is softer than diamond
    the carbons have 4 bonds
    every carbon atom has a strong bond to the other
    layers can slide/move
    graphite is in a tetrahedral arrangement
  • Consider the following reaction: N2 (g) + 3H2 (g) ⇌ 2NH3 (g) Which calculation gives ΔHΘ, in kJ, for the forward reaction?
    y + 3x − 6z
  • Why do MOLTEN ionic solids conduct electricity?
    When an ionic substance is molten the ionic lattice is broken down allowing the ions to move freely and so conduction occurs.
  • In the formation of the compound of sodium chloride
    a sodium atom donates an electron to a chlorine atom
  • For which of the following is the sign of the enthalpy change different from the other three?
    2Cl(g) → Cl2(g)
    CO2(s) → CO2(g)
    Na(g) → Na+(g) + e-
    CaCO3(s) → CaO(s) + CO2(g)
  • Which rule must be fulfilled by sharing or transferring electrons to create bonds in order for an element to be stable?
    octet rule
  • What is the formula for the cpm[ound formed when a potassium ion(K+) and a sulfide ion (S-2) unite?
    K2S
  • What is the chemical formula for the compound barium bromide?
    BaBr2
  • What is the molecular geometry of the carbonate ion? What would be the angles?
    trigonal planar; 120 degrees
  • Which statement is correct about the reaction shown? 2SO2(g) + O2(g) → 2SO3(g) ΔH = -196 kJ
    196 kJ of energy are absorbed for every mole of SO2(g)
    98 kJ of energy are released for every mole of SO2(g)
    196 kJ of energy are released for every mole of SO2(g)
    98 kJ of energy are absorbed for every mole of SO2(g)
  • What is the electron and moelcular geometry of chlorate ion? Is it polar?
    Electron: tetrahedral. Molecular : Trigonal pyramidal. : It is polar because it is both asymmetric and it is an anion. (draw please w lone pair on chlorinei
  • What is the formula for the compound formed when aluminum ions(Al 3+) and chloride ions (Cl -) unite?
    AlCl3
  • What is the suffix for all binary ionic compounds of representative elements?
    -ide
  • Which combination will give you the enthalpy change for the hydrogenation of ethene to ethane, Δ H3 ?
    − Δ H 2 + Δ H 1 − Δ H 4
  • What is the metallic ion in the compound CuCl2?
    Cu2+
  • The heat released during the combustion of C3H8(g) (propane) to produce CO2(carbon dioxide) gas and water vapour is 2222 kJ/mol of C3H8(g). Which of the following is the correct chemical equation for the reaction?
    C3H8(g)+ 5O2(g) → 3CO2(g) + 4H2O (g) + 2222 kJ
    3CO2(g) + 4H2O(g) → 5O2(g) + C3H8(g) ΔH = –2222 kJ
    C3H8(g) + 5O2(g) + 2222 kJ → 4H2O (g) + 3CO2(g)
    C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O (g) ΔH = +2222 kJ
  • How many resonance structures are there for sulphite ion? How many lone pairs?
    1 lone pair and 3 resonance structures.
  • The temperature of a 2.0 g sample of aluminum increases from 25C to 30C. How many joules of heat energy were added? (Specific heat of aluminum = 0.90 J/gK)
    9.0
  • Which combination describes the sulfate(IV) ion, SO32– (also known as sulfite ion)?
    C
    B
    D
    A
  • Maitha claims that a single sodium ion and a single oxygen ion do not bond together to form a stable binary ionic compound. Is she correct? You must explain completely
    Maitha is correct. The sum of the charges of the two ions must be zero in order for them to form a stable ionic compound.
  • What is the charge on group 1 metals?
    1+
  • Why is CHCl3 more polar than CCl4?
    CCl4 is symmetric and therefore no net dipole; CHCl3 is asymmetric
  • What is the name of the compound BaCl2
    barium chloride
  • Which of the following does NOT have an enthalpy of 0 kJ/mol
    I2(s)
    S8(s)
    H2O(l)
    Co(s)
  • Which of the following is the definition of an allotrope?
    2 or more different physical forms in which an element exist
    Different numbers of neutrons but same protons
    Different states of a compound
    The same chemical formula but a different structure
  • Which pairs of words correctly completes the statement? Ionic compounds form when____ and _____ react.
    metals ; nonmetals
  • Consider the following equation for the combustion of hydrogen: H2(g) + 1/2 O2(g) → H2O(g) + 243 kJ In order to produce 1215 kJ of heat, how many grams of H2 must burn?
    0.250 g
    12.0 g
    10.0 g
    8.00 g
  • Unknown element W has 2 valence electrons. Unknown element X has 7 valence electrons. Which formula shows the most likely outcome when elements W and X react?
    WX2
  • Calcium (Ca) is in the second column of the periodic table and is classified as an alkaline earth metal. Which of the following formulas shows the ratio of a compound formed from calcium and iodine(I)?
    CaI2
  • What is the formula for the compound sulfur hexachloride?
    SCl6
  • What is the formula for the compound formed by magnesium cation (Mg+2) and a fluoride anion (F-)
    MgF2
  • The Lewis (electron dot) structure of the ethanedioate ion is shown. Outline why all the C–O bond lengths in the ethanedioate ion are the same length
    electrons delocalized «across the O–C–O system» or RESONANCE
  • What is the energy change (in kJ) when the temperature of 20 g of water increases by 10C?
    20 x 10 x 4.18
    (20 x 283 x 4.18)/1000
    (20 x 10 x 4.18)/1000
    2 x 283 x 4.18
  • What is ΔH for the reaction below in kJ? CS2(g) + 3O2(g) → CO2(g) + 2SO2(g) (ΔHf (kJ/mol): CS2(g) = -110, CO2(g) = -390, SO2(g) = -290)
    -860
  • A chemical formula includes the symbols of the elements in the compound and subscripts that indicate
    the number of atoms or ions of each type
  • What is the enthalpy change of combustion of urea, (NH2)2CO, in kJ mol−1? 2(NH2)2CO(s) + 3O2(g) → 2CO2(g) + 2N2(g) + 4H2O(l)
    1/2 [2 × (−394) + 4 × (−286) −2 × (−333)]
    1/2 [2 × (−333) −2 × (−394) −4 × (−286)]
    2 × (−394) + 4 × (−286) −2 × (−333)
    2 × (−333) −2 × (−394) −4 × (−286)
  • Give at least 2 (two) ways to refer to this adorable looking allotrope of carbon
    any 2: Bucky ball OR C-60 OR fullterene OR buckminsterfullerene
  • The average bond enthalpies for O-O and O=O are 146 and 496 kJ/mol respectively. What is the enthalpy change, in kJ, for the reaction below? H-O-O-H(g) → H-O-H(g) + ½O=O(g)
    -102
  • Covalent bonds take place between
    two nonmetals
  • What is the electron and moelcular geometry of sulfate ion? Is it polar?
    It is tetrahedral for both electron and molecular geometry. Since it is an anion it is polar
  • What is the chemical formula for diamond?
    C(s)
  • How many covalent bonds does graphite have?
    3
  • What do sodium ions have in common with chloride ions?
    they are both cations
    they both form covalent bonds
    they are both anions
    they both have the same sized charge
  • An iron block with a mass of 0.11 kg absorbs 504J of heat energy. What is the temperature rise in K? (C = 0.448 Jg-1K-1)
    1.10
    10.23
    9.78E-2
    1.02E4
  • What is the sum of the charges in a compound?
    0
  • What is the name of the compound Ni(NO3)2
    Nickel (II) nitrate
  • [HL question] if you are in SL 5 marks automatically. Full marks for answer 1 guess only: Which of the following is a non-spontaneous process?
    A gas diffuses into a room until it is equally distributed.
    Iron exposed to water and oxygen forms rust
    Water freezes below 0°C.
    Graphite turns into diamond
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