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6. What makes Graphite so useful?

  • it is ductile and malleable, which are useful properties
  • only forms 3 covalent bonds, so slides easily, conducts electricity and high melting point
  • strong covalent bonding, allows very high melting points

7. Describe metallic bonding

  • strong electrostatic attraction between closely packed positive metal ions and the 'sea' of delocalised free electrons
  • strong bonds between atoms that requires lots of energy to break
  • strong electrostatic attraction between closely packed negative metal ions and the 'sea' of delocalised free electrons
  • strong forces of electrostatic attraction between positive nucleus and surrounding bonded negative electrons

8. What determines a Thermosoftening polymer?

  • made up of chains that are held up by weak intermolecular forces and slide easily over each other. This means it stretches easily and has a low melting point
  • held together by weak forces between chains, so it can easily melted down and remoudled
  • Lack of cross-links and use of weak low-chain plastics
  • made up of chains that are held up by strong intermolecular forces and slide easily over each other. This means it stretches easily and has a low melting point

9. What is the stationary phase in TLC (Thin-layer chromatography)?

  • thin layer of solid e.g. silica gel
  • ink
  • heated ceramic
  • copper oxide powder

10. Why are covalent bonds so strong

  • strong inter-molecular forces
  • strong forces of electrostatic attraction between positive nucleus and surrounding bonded negative electrons
  • Has a closely packed regular lattice with strong forces of electrostatic attraction between oppositely charged ions

11. What is the mobile and stationary phase for GC

  • mobile phase - solvent. stationary phase - silica gel
  • mobile phase - unreactive gas (nitrogen). stationary phase - viscous liquid (oil)
  • mobile phase - argon gas. stationary phase - sodium chloride

12. Why do ionic compounds have high melting and boiling points?

  • Strong, stable bonds between molecules
  • Has a closely packed regular lattice with strong forces of electrostatic attraction between oppositely charged ions
  • Strong electrostatic attraction between positive nuclei of a atom and negative electrons
  • Has a closely packed regular lattice with strong forces of electrostatic repulsion between oppositely charged ions