• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

In order to calculate the enthalpy change of Calcium Carbonate to Calcium Oxide, which is exceedingly hard to control and measure the energy change we must use Hess' law

Extracts from this document...

Introduction

Results CaCO Test 1 Test 2 Average Mass of CaCO Used :- 2.48g 2.49g 2.485g Temperature of HCl Initially :- 20�C 20�C 20�C Temperature of HCl after mixing with CaCO: - 22�C 22�C 22�C Total Temperature Change :- 2�C 2�C 2�C CaO Test 1 Test 2 Average Mass of CaO Used :- 1.40g 1.40g 1.40g Temperature of HCl Initially :- 19�C 20�C 19.5�C Temperature of HCl after mixing with CaO: - 38�C 36�C 37�C Total Temperature Change :- 18�C 16�C 17�C In order to calculate the enthalpy change of Calcium Carbonate to Calcium Oxide, which is exceedingly hard to control and measure the energy change we must use Hess' law which states:- "The total enthalpy change for a chemical reaction is independent of the route by which the reaction takes lace, provided initial and final conditions are the same" So therefore on adding Hydrochloric acid, which reacts readily with both, Calcium Carbonate and Calcium Oxide they both form Calcium Chloride crating a enthalpy energy triangle. ?H3 CaCO (s) CaO(s) + CO (g) ?H1 ?H2 CaCl (aq) Therefore:- ?H1 - ?H2 = ?H3 But we cannot enter our results directly into Hess' equation, we must convert them into Enthalpy energies. ...read more.

Middle

= 126136.6937 Jmol = 126 kJmol to 3sf With my result and the result produced by the data book I can calculate my percentage error. The information produced in the data book is under Standard Conditions. These conditons are:- * A pressure of 100 kilopascals * A temperature of 298K * The reactants must be in their natural physical state * All solutions must have a concetration of 1 mol dm With these accurate results from the data book I can calculate my percentage error:- Data book Information on "The Standard Enthalpy Change of Formation" ?H1 - Calcium Carbonate = -1207 kJmol ?H2 - Calcium Oxide = -635 kJmol ?H2 - Cabon Dioxide = -394 kJmol So on putting our Standard Enthalpy results into Hess's equation we get a Standard Enthalpy Change for Calcium Carbonate to Calcium Oxide:- ?H1 - ?H2 = ?H3 ==> -1207 - ((-635) + (-394)) = 178 kJmol Percentage error x 100 Standard Result - Our result Standard Result x 100 ==>178 - 126 178 =29.21% = 29% to 2 sf Evaluation Our experiment, when put into practice was not very reliable this was due to the factor of reactants surface area. ...read more.

Conclusion

There was also a problem with the chemicals used, the calcium oxide, calcium carbonate and hydrochloric acid may have been contaminated with other chemicals. It might not all have reacted the way it should have. I could nullify this by using a brand new sample of chemicals and have no interactions with other experiments or uses. This would guarantee reliable results. My method also had faults: The method did not specify a accurate measurement for Calcium carbonate and Calcium oxide, this would portray inaccurate and unreliable results, as an increase in the amount of reactants could increase the enthalpy value and could decrease the enthalpy value for a lower amount of reactants. Conclusion From my results I can tell that both reactions were exothermic, but that the reaction with calcium oxide was much more exothermic than the reaction with calcium carbonate. They were different because the bonds that were made in the calcium oxide reaction required less energy to be made than in the calcium carbonate reaction. My Hess' Law cycle can be labelled correctly:- ?H3 CaCO (s) -178 kJmol CaO(s) + CO (g) ?H1 ?H2 - 1207 kJmol -1029 kJmol CaCl (aq) If I were to do the experiment again I would enforce my changes mentioned to achieve a closer result to the Standard enthalpy value. Also I would further investigate enthalpy changes of alcohol's. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our AS and A Level Organic Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Organic Chemistry essays

  1. Thermal Decomposition of Copper Carbonate

    Attach the glass tubing on the stopper (of the test tube containing the copper carbonate) with its delivery tube under the measuring cylinder. 5. Heat the test tube with a Bunsen burner until the copper carbonate has fully decomposed.(The powder should change from blue-green to reddish brown).

  2. The aim of this experiment is to investigate the enthalpy change of combustion for ...

    However the difference between the two values does show that my results were quite accurate. I can calculate the error in my results by finding the difference between the two values and displaying this as a percentage of the calculated value.

  1. Comparing The Enthalpy Change OfCombustion Of Different Alcohols

    But we can see that there was a significantly higher percentage error in the temperature change. This error could have been reduced by using a digital thermometer which reads to 2 decimal places. This error would increase the enthalpy change of combustion by a small margin which is not a

  2. Find the enthalpy change of combustion of a number of alcohol's' so that you ...

    When doing the experiment there are going to be very slight errors when measuring due to the instruments. In actual fact there is 3 instruments, which could have slight errors, this is the electronic balance, thermometer and measuring cylinder. I am going to show how to work out the percentage

  1. The aim of this experiment is to produce Aspirin. This is an estrification in ...

    * 100 cm3 conical flask * Distilled Water * 10 cm3 pipette * 100cm3 beaker * Hirsch funnel * Water bath containing crushed ice * Goggles * Laboratory coat * Analytical balance ( 4 d.p) Method * 4.0029g of 2-hydroxbenzoic acid was weighed out on a 4.d.p balance and placed in a 100 cm3 conical flask.

  2. Comprehensive and Detailed Chemistry notes

    + H2O (l) HNO3 (aq) + HNO2 (aq) Nitrous acid then reacts with oxygen, again catalysed by air particles: 2HNO2 (aq) + O2 (g) 2HNO3 (aq) EFFECT OF ACID RAIN ON NATURAL SUBSTANCES: Acidic particle deposition and acid rain trigger the corrosion of metals and also the deterioration of paint, marble and limestone.

  1. investigating the amount of ascorbic acid present in fruit

    the titration experiment with the samples of fruit I used can be seen in appendix A, appendix B and appendix C. Appendix A gives the result for the orange sample, appendix B for the lime sample and appendix C for the lemon sample.

  2. Compare the enthalpy changes of combustion of different alcohols

    When the calorimeter is filled with the correct mass of water, I will record the starting temperature. 5) I will choose the 5 alcohols that I intend to burn. Weigh each spirit burner each time I repeat the experiment and take note of each mass.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work