To conjecture the structure and bonding of eight unknown solids by analysis of experimentally determined properties.

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IB Chemistry – Practical Report

Name: Chris Bolton

Partner: Jamie Gearing

Date(s) Conducted: 31/03/04; 02/04/04; 23/04/04

Topic: Determination of Structure and Bonding

Aim:

To conjecture the structure and bonding of eight unknown solids by analysis of experimentally determined properties.

Apparatus:

        

GENERAL:        8 unknown solids (labeled alphabetically A to H), test-tube rack

SECTION A:        Multiple 100ml beakers as required, distilled water (H2O), cyclohexane (C6H12), glass mixing rod, spatula, plastic pipette, multiple 5ml test tubes as required

SECTION B:        “Section A” equipment, graphite rods with bung, crocodile clips (x2), ammeter, power pack

        SECTION C:        Hammer (800g), wooden impact board

SECTION D:        200ml beaker, retort stand, boss and clamp, rubber band, heatproof mats, Bunsen burner, tripod and wire-ceramic gauze, thermometer (300°C capacity, ⎢error⎟ ± 0.20°C), paraffin oil, boiling tubes (x4), mortar and pestle  

        SAFETY:        Lab coat, safety glasses and plastic gloves to be worn at all times

Methodology:

Our methods were task specific, and are detailed separately in each section.  The results of each method used will assist in the determination of the structure and bonding of each substance by analysis of exhibited properties.  The experiment is documented and processed in three parts; the first pertaining to initial observations; the second to the process’ and results of each section of experiment; and the third to the interpretation of unified results from part two.

Part One: The Unknowns

A brief description of each of the unknowns is necessary a) to establish their initial state, and b) for the purpose of later reference.

Part Two: The Experiments

SECTION A: Determining Solubility

Aim of section

“To test the solubility of each of the eight unknown solids in both polar and non-polar solvents to aid in the identification of each substance as polar or non-polar and hence to assist in the determination of structure and bonding”

METHOD1 – Using the polar solvent: [distilled] Water (H2O)

  • Fill 100ml beaker with 50ml distilled water
  • Carefully add small quantity of unknown substance with spatula
  • Stir vigorously for up to 2 minutes (or until substance dissolves) with glass rod
  • Observe all significant changes

*NOTE: retain all beakers containing solutions (i.e. only for those that were soluble) for use in conductivity testing (Section B)

SAFETY1:

  • Avoid emptying contents of beakers containing solids into sink
  • DO NOT pour mixture of substance E into sink
  • Avoid unprotected contact with substance E

RESULTS1:

A Table to Show Solubility in a Polar Solvent: Water (H2O)

        Summary of results: A, C, F and G were soluble in a polar solvent.

METHOD2 – Using the non-polar solvent: Cyclohexane (C6H12)

  • Transfer 1ml of cyclohexane to 5ml test-tube via pipette
  • Carefully add small quantity of unknown substance with spatula
  • Agitate for up to 2 minutes (or until substance dissolves) with gloved finger against mouth of test-tube
  • Observe all significant changes

*NOTE: retain all beakers containing solutions (i.e. only for those that were soluble) for use in conductivity testing (Section B)

SAFETY2:

  • Avoid unprotected contact with either cyclohexane or substance E
  • Avoid emptying contents of beakers containing solids into sink
  • DO NOT pour solution of substance E into sink

RESULTS2:

A Table to Show Solubility in a Non-Polar Solvent: Cyclohexane (C6H12)

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*However an excessive quantity was added and there was a solid remnant

        Summary of results: D and E were soluble in a non-polar solvent.

NOTE: Neither H nor B was soluble in either polar or non-polar solvents

SECTION B: Conductivity Testing

Aim of section

“To test the conductivity of each of the eight unknown substances both in solution and in a solid state to give an indication of aqueous/solid conductivity, and hence to assist in determining the arrangement of electrons within the solid.”

METHOD:

  • Attach power-pack to ammeter
  • Connect a crocodile clips to each ...

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