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

Determining energy change by indirect methods

Extracts from this document...

Introduction

TO DETERMINE AN ENERGY CHANGE BY AN INDIRECT METHOD Aim: To determine the energy change in the reaction Mg(s) + H2O(l) -->MgO(s) + H2(g) Through an indirect method Apparatus: * Polystyrene cup with a lid * 100�C Thermometer (+0.5�C) * Distilled water. * 100 ml of 2 molar HCl * 0.24g of Mg ribbon * 0.1g of MgO powder * Beaker (100ml +0.1ml) * 100 ml measuring cylinder * Balance (+0.0005g) * Small beaker for holding MgO and Mg. * Sand paper * Stirrer Method: 1. Wash all the equipment with distilled water. 2. Clean the Mg ribbon with sandpaper to ensure that all the MgO that formed on it is removed. 3. Measure out 0.24g of Mg on the weighing scale. 4. Now measure 50 ml of 2 molar HCl in the 100 ml measuring cylinder. 5. Now fix a thermometer in the hole of the lid of the polystyrene cup. 6. Now in the same polystyrene cup add the 50ml of HCl and then add the 0.24g of Mg that you measured out earlier and immediately cover with the lid of the polystyrene cup(which already has the thermometer fixed in it). ...read more.

Middle

==>mass of water= mass of acid (ASSUMING) ==>specific heat capacity of water= 4.2kJ/kgK ==>change in temperature= 9.5 K = 0.05kg x 4200 J/kgK x 9.5 K = 1995J/mol = 1.995 kJ/mol This is the amount of energy which is given out for 0.24g. If we convert this to mol, we will get = (mass/molar mass) = (0.24g/24gmol-1) = 0.01mol. Therefore, for one mol the energy given out would be: 1.995 kJ/mol x 100 = 199.5 kJ/mol. For MgO= Energy change= mass x specific heat capacity x change in temperature. ==>mass of water= mass of acid (ASSUMING) ==>specific heat capacity of water= 4.2kJ/kgK ==>change in temperature= 15.1 K = 0.025kg x 4200 J/kgK x 15.1 K = 1585.5 J/mol = 1.5855 kJ/mol This is the amount of energy which is given out for 0.1g of MgO. If we convert this to mol, we'll get = (mass/molar mass) = (0.1g/ 40.3gmol-1) = 0.00248mol. Therefore, for one mol the energy given out would be: 0.00248 kJ/mol x 100 = 0.248 kJ/mol. ...read more.

Conclusion

occurred are: * Reusing the polystyrene cup can lead us to inaccurate results as the second reaction could be contaminated if the cup was not washed properly with distilled water. * The lid on the polystyrene cup was placed on it only after both the substances were put into the cup and the reaction started occurring. This would give us inaccurate results as the temperature was not measure justly as a lot of initial heat given off in the reaction was not taken into account. * The thermometers could have been influenced by the temperature outside of the cup as the experiment was being carried out next to a window. * During a couple of the trials, the lid was not able to be fixed properly on the cup. * One of the major errors was the fact that we assumed that the hydrochloric acid was equal to the amount of water. We can't really change this considering that 100% pure HCl is in gaseous state. It is an error that we must take account of though. ************ ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate 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 International Baccalaureate Chemistry essays

  1. hess's law

    After carrying out the experiment and the appropriate calculations I would also like to conclude that my hypothesis made earlier on page 2 is correct as there was a rise in temperature observed and noted when the two chemicals reacted with each other hence, proving that the chemical reaction between anhydrous copper (II)

  2. In our research project, we will try to compare the qualitative contents of some ...

    Test for Electrolyte Energy Drinks Number of Batteries Connected Conductivity of the energy drink Manipulation of Variables: Procedure/Method: A lot of simple steps need to be carried out to achieve valid data. Since four different tests are being carried out, it would be better if the steps for each test ismentioned and followed separately.

  1. Enthalpy and Hess law

    Then 50ml of HCl was measured. Then its temperature was measured. These two solutions were then mixed together in a can. The temperature change was measured using a thermometer and stopwatch. Results for route one. In table1.1, the temperatures of NaOH and 2M HCl before the reaction began were 22.5�0.1�c.

  2. Enthalpy change

    Graph 1: Graph showing the course of the measurement Using informations from the table and the extrapolations from graph, I am able to calculate the enthalpy change. ?T= temp.max - temp.min ?T= 59.8 - 30.5 ?T= 29.3�C Q= m�c�?T where m- mass of solution (g)

  1. Enthalpy Change of a Displacement Reaction

    Absolute uncertainty=3.8kJ � 8%=�0.3kJ 2. The heat released by the warm water. a) The mass of warm water. m(water)=?(water)�V(water) =1g/mL�50mL =50g Absolute uncertainty=�1mL (Assume that the absolute uncertainty of ?(water) is negligible) % uncertainty=1/50 � 100%=2% b) The change of the temperature ?T is the temperature change after the warm water was added into the cold water.

  2. To determine the standard enthalpy of formation of Magnesium Oxide using Hess Law.

    For 120 seconds, 24 readings were taken and noted in a pre-made data collection table. 9. Once 120 seconds were up, the calorimeter was emptied and cleaned so that another trial of the same experiment could be performed. Safety Precautions: 1.

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