RP2, calorimetry

• Objective of this RP

  substance are mixed together, in an insulated container and temperature change is measured

  -solids dissolving or 2 solutions reacting together
• Method for calorimetry

  -wash equipment with solutions being used, dry

  -put polystyrene cup in glass beaker for insulation and support

  -measure out desired volumes of solutions with volumetric pipettes and transfer to cup

  -clamp thermometer into place, making sure its immersed

  -measure initial temp every min for 2-3 min

  -add solid, stir

  -record temp every min after addition for several minutes

  -extrapolate curve back to time reactants were added
• Why is extrapolation needed?

  if reaction is slow then exact temperature rise will be hard to obtain as cooling is happening simultaneously with the reaction
• What needs to be done when measuring temp with 2 solutions?

  -temp of both solutions need to be measure before addition and average temp is used
• Errors for calorimetry

  -energy transfer to surroundings, heat loss

  -approximation of specific heat capacity

  -neglecting of specific heat capacity

  -reaction or dissolving may be incomplete

  -density taken to be same as water
• measuring enthalpy using flame calorimetry

  -fuel burnt and flame is used to heat water in a metal cup
• Measurement needed for flame calorimetry

  -measure mass spirit burner before and after

  -temperature change of water

  -volume of water in cup
• Errors when doing flame calorimetry

  -energy loss to environment, heat loss

  -incomplete combustion of fuel

  -evaporation fuel after weighing

  -specific heat capacity