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

Enthalpy Change

Extracts from this document...

Introduction

Skill P - Planning * The aim of this practical experiment is to determine the enthalpy change for this reaction by an indirect method based on Hess's Law. Both Calcium Oxide and Calcium Carbonate react readily with 2 mol dm Hydrochloric Acid solutions. The temperature changes during these reactions can be measured and the enthalpy changes calculated. * Chemicals and apparatus: * 250 cm measuring cylinder * 2 mol dm Hydrochloric Acid * 250 cm beaker * 0 - 10 0� C thermometer (graduations to 1� C ) * 2.4 - 2.6 g of Calcium Carbonate * 1.3 - 1.5 g of Calcium Oxide * Procedure 1. Weigh out a weighing bottle containing between 2.4 and 2.6 g of Calcium Carbonate 2. Weigh out a weighing bottle containing between 1.3 - 1.5 g of Calcium Oxide 3. Using the measuring cylinder provided place 50 cm3 of 2 mol dm-3 hydrochloric acid (an excess) into a 250 cm3 glass beaker. 4. Measure the temperature of the acid using the thermometer provided. 5. Add the calcium carbonate/ calcium oxide to the acid. 6. Take the temperature again when the reaction is complete. ...read more.

Middle

4.2 7 H= 1514.1 We have to calculate the molar heat. Therefore, 1 mole of CaO = 40 + 16 = 56 KJ mole CaCO CaCl We can calculate based on Hess's Law. Therefore, Hence, = CaO = -18.19 - (- 56.52) = 38.33 KJ mole (Endothermic reaction) Skill E - Evaluating Evidence A balance was used fact that leads to limited accuracy, because it is open to the air and is susceptible to outside forces. The procedure was good and the mix of reactants was intimate, so we can say that the experiment were suitable. The first reaction (CaCO) was a very slow reaction. Therefore, when reading the temperature we had to check it constantly and pick up the biggest value. The second one (CaO) was a very fast reaction, so when reading the temperature, we had to choose the first biggest value, because after that that point the temperature will decrease and the results will be anomalous. 2.42 g of CaCO and 1.50 g of CaO was taken with a tendency to show variation of 0.01g. This will lead to 0.004% error for CaCO and 0.006% for CaO. ...read more.

Conclusion

A greater proportion of molecules exceed the activation energy at higher temperature. The reaction takes place quicker if the reactant, hydrochloric acid, is more concentrated, because there are more molecules per volume and they will exceed the activation energy. This thing applies to the first reaction which involved CaCO, and which was very slowly because it was in lumps form. So, the first experiment could be considerable improved by turning the CaCOin powdered form. In order to find out the enthalpy change we used Hess's Law which shows that whatever the route from given reactants to products, the overall energy change must be the same. Therefore, each of the two enthalpies calculated from the two experiments count half per cent on the final conclusion. Hence, CaCO 2.42 0.01g 0.4 % error on final conclusion + the temperature change CaO 1.50 g 0.01g 0.6 % error on final conclusion + the temperature change A considerably effect on the validity of the final conclusion have the signs of the heat evolved (whether the reactions are endothermic or exothermic). The first two experiments are exothermic reactions and as the final enthalpy change has a positive value, the reaction is an endothermic one. ...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 Inorganic 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 Inorganic Chemistry essays

  1. Peer reviewed

    Determining the concentration of acid in a given solution

    5 star(s)

    This means that 0.00253 moles of Na2CO3 reacted. The sodium carbonate and sulfuric acid react in a 1:1 ratio This means that 0.00253 moles of sulfuric acid reacted with the sodium carbonate, so there is 0.00253 moles of this concentration of sulfuric acid in 24.60cm3. Concentration (mol dm-3)

  2. Peer reviewed

    Deducing the quantity of acid in a solution

    5 star(s)

    * Sodium Carbonate We used solution of sodium carbonate both as a solution and as powder. Its concentration is 0.1 M, so it can not be labelled as irritant because only solutions equal to or stronger than 1.8 M are irritant.

  1. effects Concentration and Temperature on the Rate of Reaction

    Figure 4 shows the change when the temperature is increased by 10K. It shows that there is still a wide range of energies but now there are more particles with a higher kinetic energy. At the higher temperature of 310 Kelvin there are many more molecules which have reached the activation enthalpy level than at 300K.

  2. Lab report Determination of Enthalpy Change of Neutralization

    So, No of mole of H2O = 0.05 mol Heat given out per mole of H2O formed = 2738.772826 / 0.05 = 54.8 KJ mol-1 The enthalpy change of neutralization is -54.8 KJ mol-1 Reaction 3: Mass of the solution = (25 + 25)

  1. Thermal Decomposition of Calcium Carbonate

    = - 2.1 J The energy transfer has a negative value, as the reaction was exothermic. This can be seen by the increase in temperature after the reaction. To work out H1 we need to find the energy transfer per 1 mole of calcium oxide, but first I need to

  2. Finding Out how much Acid there is in a Solution

    Table of Results This table shows the results of all the titrations that I completed. All results are to two decimal places and anomalous results written in red. Titration Rough 1 2 3 4 5 Final burette reading (cm3) 1.90 1.55 0.40 0.90 0.70 0.85 Initial burette reading (cm3)

  1. Scientific Practical Techniques

    have done this I did the same thing for pH 4 and for the other unknown PH To improve the measurement and get accurate result, I would suggest

  2. Determination of the solubility of calcium hydroxide

    read to at least two decimal places, uncertainty of +0.02g * Clean burette, uncertainty of +0.05cm-3 * Clean 25cm-3 pipette, uncertainty of +0.05cm-3 * Two clean beakers 100 cm3. (Readings on it are irrelevant) * Conical flask * Pipette filler * Distilled water * White spotting tile * Clamp, boss

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