Objectives & Procedures: Calorimetry – Thermodynamics – Temperature Experiments

1.1 – Intro to Calorimetry

Learning Objectives

  • Understand the concept of heat and joules.
  • Perform heat-gain and heat-loss calculations.

Procedure Overview

  • Hot and cold water are mixed. The water masses and temperature changes are used to calculate the heat lost and heat gained.
  • Ice is melted in water and the heat of fusion is calculated.
  • Candle is burned under a metal cup containing a known mass of water, and the heat of combustion of the candle is calculated.

1.2 – A Hess’ Law Investigation

Learning Objectives

  • Measure the heats of reaction for two chemical reactions.
  • Use Hess’s Law, in conjunction with the above measurements, to calculate the heat of reaction for the combustion of magnesium metal.

Procedure Overview

  • Time/temperature program used with a Styrofoam cup calorimeter.
  • )T values are determined graphically for Mg/HCl and MgO/HCl reactions.
  • Hess’s Law is used to determine the heat of combustion of Mg.

1.3 – Enthalpy of Hydration & Solution

Learning Objectives

  • [soln] – Qualitatively correlate the ªH of several compounds with their properties such as ionic charge, ionic size, etc.
  • [4 4 2] – To quantitatively determine the enthalpy of solvation of MgSO and MgSO • 7H O
  • [4 2] – To quantitatively determine the enthalpy of the water of hydration in MgSO • 7H O

Procedure Overview

  • [soln] – Qualitatively determine Q of ammonium nitrate, sodium chloride, lithium chloride, sodium hydroxide, sodium nitrate, sodium sulphate, and 0.50 mL of conc. sulphuric acid.
  • [soln 4 4 2] – Quantitatively determine Q of 2, 4, 6 and 8 g of MgSO and MgSO • 7H O
  • [soln soln 4 4 2] – Calculate Q per gram, and ªH per mole of MgSO and MgSO • 7H O from linear curve fits of the 2,4,6 and 8 g experiments.
  • [Hydration 4 2] – Calculate the ª for MgSO • 7H O

1.4 – Hot Packs, Cold Packs, & Heats of Solution

Learning Objectives

  • [soln] – Use the MicroLAB interface to measure the heats of solution ()H , in kJ/mol) of several salts.
  • Calculate the heats of formation ()Hf , in kJ/mol) of single aqueous ions.
  • Predict the heats of solution of additional salts.
  • Design a hot pack and a cold pack for specified temperature changes.

Procedure Overview

  • The MicroLAB interface is used to measure temperature changes in a Styrofoam cup calorimeter.
  • )T values are determined graphically for the dissolution of four salts.
  • [soln] – )H calculated for each salt.
  • [f] – )H calculated for the ions in each of the four salts.
  • [f soln] – )H values for the ions used to find )H for two additional salts.
  • [4 3 4.] – A cold pack designed using NH NO , and a hot pack designed using MgSO

1.5 – Enthalpy & Entropy of Zinc w/ Copper Sulfate

Learning Objectives

  • Determine changes in enthalpy and entropy of the reaction of zinc with copper sulfate using two methods: electrochemistry and calorimetry.
  • Compare the enthalpy values obtained by the two methods.

Procedure Overview

  • [4 4(aq)] -A simple electrochemical cell Cu(s)/CuSO (aq) // ZnSO / Zn(s) is constructed in a Chem-Carrou-Cell™ and voltages are measured at different temperatures.
  • A spreadsheet is used to plot a linear regression graph of voltage versus temperature, and the graph is used to calculate the enthalpy and entropy changes for the cell reaction.
  • [4] – Heat of reaction of zinc powder with 0.5 M CuSO solution is determined calorimetrically.

5.1 – Freezing Point of Glacial Acetic Acid

Learning Objectives

  • Demonstrate the general features of a cooling curve.
  • Measure the freezing point of a compound.

Procedure Overview

  • Temperature probe calibration at a minimum of three points between 0°C and 55°C.
  • Testing the experiment program and temperature probe.
  • Apparatus assembly and warming of glacial acetic acid sample.
  • Data collection for cooling curve with supercooling and spreadsheet treatment of data.

5.2 – Freezing Point of Phenyl Salicylate

Learning Objectives

  • Demonstrate the general features of a cooling curve.
  • Measure the freezing point of a compound.

Procedure Overview

  • Guided writing of an experiment program.
  • Temperature probe calibration at a minimum of three points between 0°C and 55°C.
  • Apparatus assembly and warming of phenyl salicylate sample.
  • Data collection for cooling curve with supercooling and spreadsheet treatment of data.

3.1 – Determining the Coordination Number of Ni2+ and Cu2+ by Enthalpy

Learning Objectives

  • Investigate the formula of the complexes formed between Ni2+ and ethylenediamine (en) and between Cu2+ and “en”.
  • Determine the maximum number of “en” molecules that will bind to Ni2+ and Cu2+ by making heat of reaction measurements with the MicroLAB interface.
  • Calculate heats of reaction for the various Ni2+ /”en” and Cu2+ /”en” complexes.

Procedure Overview

  • A series of experiments is done with the [Ni(OH2)6] complex to determine the number of “en” 2+ molecules which will bind to Ni . One mole of [Ni(OH2)6] is reacted with 1, 2, 3, and 4 moles 2+ 2+ “en”. A comparison of ªH values is used to identify the maximum number of “en” ligands bonded to the Ni2+ ion.
  • A series of experiments is done with the [Cu(OH2)6] complex to determine the number of “en” 2+ molecules which will bind to Ni . One mole of [Cu(OH2)6] is reacted with 1, 2, 3, and 4 moles 2+ 2+ “en”. A comparison of ªH values is used to identify the maximum number of “en” ligands bonded to the Cu2+ ion.