Lesson 2B.2

2B.2 Predicting structure and physical properties Quiz: Pearson Edexcel Chemistry, Unit 2

20 questions

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Lesson 2B.2, Predicting structure and physical properties: 20 multiple choice questions for the Pearson Edexcel Chemistry (9CH0), Unit 2: Bonding and Structure, written with Revision Ninja.

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The 20 questions

  1. A substance has a high melting temperature, conducts when molten, and dissolves in water. What is the most likely structure?

    • Giant metallic
    • Giant covalent
    • Simple molecular
    • Giant ionic
  2. A substance has a low melting temperature, does not conduct, and dissolves in hexane but not in water. What is its likely structure?

    • Giant metallic, with delocalised electrons that conduct well and dissolve in both water and hexane easily
    • Simple molecular, non-polar
    • Giant ionic, with strong electrostatic attraction between ions that dissolve only in polar solvents such as water
    • Giant covalent, with a rigid network of strong bonds that dissolves in neither water nor hexane at all
  3. A substance has a high melting temperature, conducts when solid, and is malleable. What is its likely structure?

    • Giant covalent
    • Giant metallic
    • Giant ionic
    • Simple molecular
  4. Predict whether solid NaCl conducts electricity, and whether molten NaCl conducts.

    • Neither conducts electricity in either state, because ionic compounds contain no free electrons to carry charge
    • Both solid and molten NaCl conduct electricity, because the compound contains ions in both of its states
    • Solid conducts electricity and molten NaCl does not, because the lattice collapses and loses its ions on melting
    • Solid does not conduct, molten does conduct, because ions are fixed in the solid but free to move when molten
  5. A substance melts at 25 degrees Celsius, is a liquid at room temperature, and does not dissolve in water. What is its likely structure?

    • Simple molecular with weak London forces
    • Giant covalent, with strong bonds throughout the solid that resist melting until very high temperatures are reached
    • Giant metallic, with delocalised electrons that give the solid a high melting temperature and good conductivity
    • Giant ionic, with a regular lattice of ions held together by strong electrostatic forces throughout the solid
  6. A substance melts at 3500 degrees Celsius, does not conduct, and is insoluble in all solvents. What is its likely structure?

    • Giant metallic
    • Simple molecular
    • Giant ionic
    • Giant covalent
  7. A student claims that a compound which conducts when molten must be ionic. Evaluate this claim.

    • Invalid, because only metals conduct electricity, so the compound must be a metal rather than an ionic compound
    • Partly valid: conduction when molten suggests mobile ions, but it does not on its own rule out other possibilities, so more data is needed
    • Invalid, because conduction when molten never occurs for ionic compounds, which conduct only when they are dissolved
    • Fully valid, because any molten substance that conducts electricity must be an ionic compound with mobile ions in it
  8. Which property is the best evidence that a substance has a giant covalent structure?

    • Low melting temperature together with solubility in hexane, which points to weak forces between separate molecules
    • High solubility in water together with conduction when molten, which points to a giant ionic lattice of ions
    • Very high melting temperature together with insolubility in all solvents
    • Conduction in the solid state together with malleability, which points to delocalised electrons in a metal
  9. Why does sodium chloride have a high melting temperature?

    • Many strong electrostatic attractions between oppositely charged ions in a giant lattice must be overcome
    • Its delocalised electrons bind the ions together tightly, so a great deal of energy is needed to melt it
    • Its covalent bonds are very strong and must each be broken before the solid can melt into a liquid
    • Its molecules are held together by hydrogen bonds that are strong enough to resist melting in the solid
  10. Predict whether CO2 or SiO2 has the higher boiling temperature.

    • CO2, because its carbon-oxygen double bonds are stronger than the bonds in silicon dioxide and so boil higher
    • SiO2, because it is a giant covalent lattice whereas CO2 is a simple molecular gas
    • CO2, because it has a higher molar mass than silicon dioxide, so its molecules are held more strongly together
    • They boil at the same temperature, because both are oxides of Group 4 or Group 14 elements in the periodic table
  11. A substance has a melting point of -20 degrees Celsius, does not conduct, and dissolves in water through hydrogen bonding. What is its likely structure?

    • Giant metallic, with a lattice of positive ions surrounded by a sea of delocalised electrons in the solid
    • Simple molecular with hydrogen bonding
    • Giant ionic, with a lattice of oppositely charged ions held together by strong electrostatic attraction in the solid
    • Giant covalent, with a three-dimensional network of strong covalent bonds linking every atom in the solid
  12. A solid has a melting point of 98 degrees Celsius, is soft, and conducts electricity in the solid state. What is the most likely bonding?

    • Metallic bonding with weaker metallic attraction, such as in a Group 1 metal
    • Simple molecular London forces, with small molecules held together weakly and separated easily on heating
    • Covalent bonding in a giant network, with strong bonds linking each atom to its neighbours in every direction
    • Ionic bonding in a giant lattice, with oppositely charged ions held together by strong electrostatic attraction
  13. Which property is best evidence for a simple molecular structure?

    • Solubility in water together with conduction when dissolved, which points to an ionic compound that ionises
    • High melting temperature together with conduction when molten, which points to a giant ionic lattice of ions
    • Low melting and boiling temperatures, with no conduction in any state
    • Malleability together with conduction when solid, which points to delocalised electrons in a metallic lattice
  14. Explain why a substance that is a non-conducting solid and dissolves in water, but conducts only when dissolved, is most likely ionic.

    • Its metallic bonds become stronger in solution, which lets the dissolved particles carry the electric current
    • Its covalent bonds break in water to release free electrons, which carry the electric current through the solution
    • Its ions are fixed in the solid lattice, but when dissolved they separate and are free to move and carry charge
    • Its molecules are polar, and dissolving makes them conduct electricity as dipoles that move through the solution
  15. Predict whether propan-1-ol is soluble in water and explain why.

    • Soluble, because its O-H group forms hydrogen bonds with water molecules
    • Soluble, because the molecule is ionic and dissociates into ions in water, which then dissolve easily
    • Insoluble, because the molecule is non-polar overall and so cannot mix with the polar water molecules
    • Insoluble, because its alkyl chain repels water so completely that no hydrogen bonding can form with the molecule
  16. Explain why the melting temperatures of Group 1 metals fall down the group.

    • The atoms and ions get larger, so the delocalised electron density per ion falls and the metallic bonding weakens
    • The metals lose delocalised electrons as the group is descended, so there are fewer electrons to hold the lattice
    • The atoms gain protons as the group is descended, so the metallic bonding is weakened by the extra nuclear charge
    • The metals become covalent down the group, so their bonds are weaker and the lattice melts more easily
  17. Two solids both melt at 1700 degrees Celsius. X does not conduct in any state, and Y conducts as a solid and as a liquid. Explain the difference.

    • X is metallic and Y is ionic, because metals always melt at higher temperatures than ionic compounds do in general
    • X is giant covalent with no mobile charge carriers, while Y has delocalised electrons in a metallic lattice
    • X contains delocalised electrons, which Y lacks, so X should conduct better than Y does in both states of matter
    • X is simple molecular and Y is covalent, because Y conducts electricity and simple molecular solids never conduct
  18. Why is SiO2 insoluble in water while NaCl dissolves?

    • SiO2 is giant covalent, and water cannot break its strong network of bonds, whereas water hydrates the ions of NaCl
    • SiO2 is ionic and forms a precipitate with water, which is why it does not dissolve in the water solution at all
    • NaCl is covalent and reacts with water to form new bonds, which is why it dissolves in the water readily
    • Water is non-polar, so it dissolves NaCl only in the presence of SiO2, which acts as a catalyst for the solution
  19. Which substance is most likely to be a giant ionic lattice?

    • Magnesium oxide, which melts very high and conducts when molten
    • Diamond, which is hard and insoluble in all solvents because its network of covalent bonds is very rigid
    • Ice, which is held together by hydrogen bonds between small molecules and melts at a low temperature
    • Iodine, which melts at a low temperature, does not conduct, and forms small molecules with weak London forces
  20. Which substance would be expected to be soluble in water and have a low melting temperature?

    • Copper, a giant metallic lattice whose delocalised electrons hold the atoms together with strong attraction
    • Ethanol, which forms hydrogen bonds with water
    • Silicon(IV) oxide, a giant covalent network whose strong bonds resist breaking by water or by heat
    • Graphite, a giant covalent layered solid whose layers are held by strong bonds within each sheet of the structure

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