Diagnostic Corrections

• Electronegativity corrections


  The ability of an atom in a covalent bond to attract a pair of electrons
• Explain why the C-Cl bond is polar

  Carbon is delta positive and chorine is delta negative

  Because carbon has a lower electronegativity than chlorine
• Why is C-Cl polar but not CCl4?

  CCl4 is tetrahedral meaning there is even distibution of electron density

  So the dipoles will cancel out
• What causes VDW forces between non-polar molecules?

  Electrons are always moving so delta positive and negative charges arise by chance i.e. temporary dipoles

  The delta positive region attracts the electron density in the next molecule creating a dipole in the next molecule i.e. an induced dipole

  The attraction between the two molecules is VDW
• Identify the yellow precipitate formed

  Silver iodide
• t=


  1/0.053=18.7
• State and explain how the reaction for 1-bromobutane compares with the 1-iodobutane and predict how the graph will differ

  Bromines reaction is slower

  The carbon halogen bond must break ... the c-br bond is stronger than the c-cl bond --> breaking it requires more energy input + reaction slows

  The line for 1-iodobutane will be lower at all tempeartures
• Outline how to use the infrared spectrum to determine whether the compound is pent-1-ene or 2-methylbut-2-ene

  Since the compounds have the same functional groups their IRS are similar

  The fingerprint region is where the spectre differs

  So look for an exact match in the fingerprint region to a known spectrum on a database
• What is the name of CFCl3?

  trichlorofluoromethane
• What are the propagation equations for the conversion of CHFCL2 into CFCl3?


  CHFCl2 + Cl* --> HCl + *CFCl2

  *CFCl2 + Cl2 --> CFCl3 + Cl*
• How does CFCl3 break down in the upper atmosphere to form chlorine free radicals?

  CFCl3 --> *CFCl2 + *Cl
• Give two equations to show how chlorine free radicals decompose ozone


  Cl* + O3 --> ClO* + O2

  ClO* + O3 --> Cl* + 2O2
• Outline a series of test tube reactions that the student can use to identify ammonium nitrat, potassium sulfate, sodium carbonateand magnesium nitrate.


  NaOh to all, positive is white precipitate of Mg(Oh)H
• State in terms of electrons the meaning of the term oxidising agent

  Electron acceptor
• What is the half equation that shows the reduction of NO3- in acidic solutions to NO2

  NO3- + e- + H+ --> NO2 + H2O
• What is the overall equation for the reduction of NO3- ions by copper?

  2NO3- + Cu + 4H+ --> Cu2+ + 2NO2 + 2H2O
• Suggest why water is not a suitable solvent for a reaction with bromoethane and sodium cyanide

  Because the polarity of water dissolves ionic sodium cyanide but not organic bromoethane