Practical Chemistry

Experiment 10: Determining the relative molecular mass of a volatile liquid


To measure the relative molecular mass of a series of volatile liquids by direct means


The students have studied the gas laws and are provided with three volatile liquids, gas syringes and seals. They are first given an introductory calculation.

Instructions given

  • Weigh a gas syringe and seal.
  • Introduce a small quantity of the volatile liquid into the syringe and close the end using a rubber seal.
  • Place in a preheated oven and leave until maximum expansion is observed
  • Record the volume in the syringe, the temperature of the oven and the mass of the syringe and seal
  • Repeat for the different samples cooling and cleaning the syringe before use each time.

Experimental report

The following factors will be assessed:-

  • Accurate recording of raw data
  • Presentation of raw data
  • Data analysis and presentation
  • Evaluation of errors both qualitative and numerical

Relevant criteria

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