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

Application of Hess(TM)s law to Determine the Enthalpy Change of Hydration of Magnesium Sulphate(VI)

Extracts from this document...

Introduction

Experiment 6 Date: 18-10-2005 Application of Hess's law to Determine the Enthalpy Change of Hydration of Magnesium Sulphate(VI) Objective To determine enthalpy change of hydration of magnesium sulphate (VI) . Introduction The enthalpy of a substance refers to its total energy content. During reactions, the enthalpy of the substances involved changes. This is known as the enthalpy change of a substance. Enthalpy change of substances from their initial states to their final states is independent of the pathways. This means that no matter how many reactions the reactants undergo to form the same products, the change in enthalpy is always the same. This principle governing the change of enthalpy of substances is known as the Hess's Law. For example, a certain amount of magnesium sulphate (VI) powder is dissolved in distilled water, and the enthalpy change, H1 is recorded. Magnesium sulphate (VI)-7-water is also dissolved in water and its enthalpy change, H2 is also recorded. By Hess's Law, the enthalpy change for magnesium sulphate to turn to magnesium sulphate -7-water is equal to H1 - H2, as shown in the above born-haber cycle diagram. The enthalpy change for the crystallization of magnesium sulphate is not measured directly because the reaction does not favour the direct measurement of the enthalpy change. ...read more.

Middle

Discussion 1. When the temperature of the solution has a different temperature than its surroundings, energy will be transferred from the higher area to the lower area. So, the temperature of the solution, after the reaction, will eventually restore the temperature of its surroundings. The longer the time used in the reaction, the more the heat lost to the surroundings. Therefore, the longer the time used in the reaction, the more inaccurate the results would be. For example, it took a long time for the anhydrous magnesium sulphate to dissolve fully in water. So, a large amount of heat is lost to the surroundings. Although only the greatest temperature change is needed, the temperature loss still has a bad effect on the accuracy of the experiment. In order to reduce the errors in this experiment, we need to shorten the time. How can we shorten the time? We can speed up the dissolution process of the anhydrous magnesium sulphate by adding a larger volume of water. With a larger volume of solute, the magnesium sulphate crystals will be more easily dissolved. Also, we can speed up the reaction by using heated distilled water. ...read more.

Conclusion

This is because while I was doing my experiment, the sun was rising and the temperature was rising higher and higher. Second, I assumed no heat loss to the surroundings. If there were heat loss, which was actually the case, I would have to consider the heat loss to the surroundings. There is a method to take into account the heat loss to the surroundings, but it is not a good method when the reaction takes a long time to complete. Also, as the final temperature does not have great difference from the surroundings, the heat loss can be neglected. 6. Why cannot the molar enthalpy change of hydration of magnesium sulphate (VI) be measured directly in the laboratory? The reason why the molar enthalpy change of hydration is not measured directly can be traced back to how crystallization is carried out. The saturated solution of magnesium sulphate is to be left in a certain place for a long time until the water evaporates and crystals are formed. This method takes a long time. As mentioned above, the longer the time of reaction, the larger the heat loss. So, in this method of preparation involved a large amount of heat loss and the results would be extremely unreliable; the solution would maintain a constant temperature throughout the whole experiment. So, the enthalpy change cannot be measured directly. ...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 Physical 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 Physical Chemistry essays

  1. Marked by a teacher

    Heat of Neutralization. Objective: To investigate the ...

    5 star(s)

    Further Discussion for the QA section: 7. When calculating the enthalpy change of neutralization in the experiment, we would consider the heat absorbed by the cup, lid, thermometer and the rest of the surroundings negligible, as polystyrene foam is a good insulator, even though some heat would be absorbed by

  2. Application of Hesss law to Determine the Enthalpy Change of Hydration of Magnesium Sulphate(VI)

    Data and Calculation Enthalpy change of anhydrous magnesium sulphate Weight of polystyrene cup=1.936g Weight of bottle and anhydrous magnesium sulphate= 7.678g Weight of empty bottle= 4.66g Mass of anhydrous magnesium sulphate= 3.018g Number of moles of anhydrous magnesium sulphate= 3.018/ (120.4)

  1. Determination of the Number of Water of Crystallization in Oxalic Acid Crystals

    To be determined 25 cm3 Burette solution Potassium permanganate To be determined Indicator N/A Titration no.

  2. Enthalpy Change of the Hydration of Magnesium Sulphate

    State Hess's law. Hess's law states that the energy change for any chemical or physical process is independent of the pathway or number of steps required to complete the process provided that the final and initial reaction conditions are the same.

  1. Investigating the Rate of the Reaction between Bromide and Bromate Ions in Acid Solution

    I also used burettes as opposed to measuring cylinders to measure out volumes of reactants, which gives a lower percentage error than a measuring cylinder would have. However, it is possible that my method led to errors. These procedural errors are discussed below (4.2, page 47).

  2. Determination of the enthalpy change of neutralization

    + HCl(aq) --> H2O(l) + NaCl(aq) or NaOH(aq) + CH3COOH(aq) --> H2O(l) + CH3COOHNa(aq) The mole ratio of sodium hydroxide to acid is 1:1. Therefore, the concentration of sodium hydroxide is also 1.00M. c) Energy change of hydrochloric acid = mc?T = (20+20)

  1. To determine enthalpy change of hydration of magnesium ...

    Hydrochloric acid Experiment No: 1 2 Mass of CaCO3 used / g 2.13 2.05 Molar mass of calcium carbonate = 100 g/mol Volume of hydrochloric acid used = 100 cm3 7)

  2. Describe the construction, operation and application of distillation equipment used in industry

    c downcomers. A downcomer consists of an active area where mass-transfer takes place. A downcomer is in place to move the liquid from tray-to-tray with an open area where vapour-liquid disengagement takes place and the vapour moves from tray-to-tray. The purpose is to provide extra front's where condensation can occur.

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