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

Our aim in this experiment to measure the heats of reaction for three related exothermic reactions and to verify Hesss Law of Heat Summation

Extracts from this document...

Introduction

HEATS OF REACTION - HESS'S LAW INTRODUCTION: Our aim in this experiment to measure the heats of reaction for three related exothermic reactions and to verify Hess's Law of Heat Summation.By calculating temperature differences and calculating the energy lost or gained we are going to calculate the heats of reactions.Heats of reactions will be found by dividing the heat released to the moles of matter NaOH used. NaOH(s) --> Na+(aq) + OH-(aq) Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) --> H2O + Na+(aq) + Cl-(aq) NaOH(s) + H+(aq) + Cl-(aq) --> H2O + Na+(aq) + Cl-(aq) Hess's law states that energy changes are state functions. The amount of energy depends only on the states of the reactants and the state of the products, but not on the intermediate steps. Energy (enthalpy) changes in chemical reactions are the same, regardless whether the reactions occur in one or several steps. The total energy change in a chemical reaction is the sum of the energy changes in its many steps leading to the overall reaction. http://www.science.uwaterloo.ca/~cchieh/cact/c120/hess.html REACTION 1: NaOH(s)=Na(aq)+OH(aq) ...read more.

Middle

of 0,50M H + Cl trial2 22 26 26 26 25,5 25,5 50ml(�0,1) of 0,50M Na + OH, 50ml(�0,1) of 0,50M H + Cl trial3 22 25 25,3 25 25 25 50ml(�0,1) of 0,50M Na + OH, 50ml(�0,1) of 0,50M H + Cl Graph4:temperature - time graph of Na(aq) + OH(aq) + H(aq) + Cl(aq) = Na(aq) + Cl(aq) + H2O(l) for trial 1. Graph5:temperature - time graph of Na(aq) + OH(aq) + H(aq) + Cl(aq) = Na(aq) + Cl(aq) + H2O(l) for trial 5. Graph6:temperature - time graph of Na(aq) + OH(aq) + H(aq) + Cl(aq) = Na(aq) + Cl(aq) + H2O(l) for trial 6. CALCULATIONS FOR REACTION 2 Volume of 0,50M HCl used: 50ml(�0,1) Volume of 0,50M NaOH used: 50ml(�0,1) Mass of solution : 50g(�0,1)HCL+50g(�0,1)NaCl=100g(�0,1) Initial temperature of HCL solution:22,5C(r)(�0,1) Initial temperature of NaCl solution:23C(r)(�0,1) Final temperature of solution:24,2C(r)(�0,1) ?t=24,2C(r)(�?0,04) - 22,8 C(r)(�?0,04)=1,4(�?0,1) Final temperature of solution:25C(r)(�0,1) ?t=25C(r)(�?0,04) - 22,8 C(r)(�?0,04)=2,2(�?0,1) Final temperature of solution:25,5C(r)(�0,1) ?t=25,5C(r)(�?0,04) - 22,8 C(r)(�?0,04)=2,7(�?0,1) ?T average=2,1(�?0,1) Q=MC?T =100 g(�%0,1)*4,18*2,1(�%0,1)=877,8(�%0,2)j =0,9(�%0,2)kj 1000ml=1l =50 ml(�?0,2) =0,05l(�?0,2) =0,05l(HCL)*0,50mol/l(HCL) =0,025 mol HCL =0,05(�?0,2)l(NaOH)*0,50mol/l(NaOH) =0,025 mol(NaOH) (�?0,2) Heat of reaction=0,9(�%0,2)KJ/0.03(�?0,2)= - 30(�?0,4) REACTION 3 NaOH(s) + H+(aq) + Cl-(aq) --> H2O + Na+(aq) + Cl-(aq) ...read more.

Conclusion

� Na+ + OH- Reaction 3 NaOH (s) + H+ + Cl- � Na+ + Cl- + H2O Volume H2O or HCl used (mL) 50 50 Mass of solid + container (g) 42 42 Mass of empty container (g) 41,4 41,4 Mass of solid used (g) 0,6 0,6 Initial water/HCl temperature (�C) 23 22,5 Final water/HCl temperature (�C) 25,6 27,6 Change in temperature (�C) 2,6 5,1 Reaction 2 Na+ + OH- + H+ + Cl- � Na+ + Cl- + H2O Volume NaOH solution (mL) 50 Volume HCl solution (mL) 50 Total solution volume (mL) 100 Initial temperature HCl solution (�C) 22,5 Initial temperature NaOH solution (�C) 23 Average temperature (�C) 22,8 Final temperature of mixture (�C) 24,9 Change in temperature (�C) 2,1 CONCLUSION: NaOH(s) --> Na+(aq) + OH-(aq) Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) --> H2O + Na+(aq) + Cl-(aq) +____________________________________________ NaOH(s) + H+(aq) + Cl-(aq) --> H2O + Na+(aq) + Cl-(aq) ?H1+?H2=-30+(-30) = -60= ?H3 But the ?H3 found in the end of the experiment is -50. Percent difference = ?H3-( ?H1+ ?H2)/ ?H3 *100 -50(-30+ -30)/-50*100 =? 20 In the end the heats of reactions are measured and the Hess law is verified. CHEMISTRY EXPERIMENT HEATS OF REACTION - HESS'S LAW Beril Kologlu 41831 11-F ...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

    Controlled Variables: The volume of distilled water used i.e. 50 cm3 was kept constant by using a measuring cylinder to measure the volume, the temperature and pressure at which the experiment was conducted was also kept constant by conducting the experiment from the beginning till the end in the same room and the room temperature was monitored and the

  2. Electrochemical cells - investigate the effect of the temperature change of the anode electrolyte ...

    hot plate, since its reach the certain temperature, when turn off the hot plate, actully the remaining heat still heat the electrolyte, therefore, the actually temperature will always be a liitle bit higher than recording data. it will affect the average voltage, the results may be a little bit lower than recorded data.

  1. Hesss Law Lab, use Hesss law to find the enthalpy change of combustion of ...

    It had same texture as water. Magnesium metal strip Its color was dull silver and it was a grey strip before cleaning but was shiny after I rubbed it with a sand paper. It was very ductile. Magnesium oxide It was a fine white powder and it looked like floor.

  2. Using Hess's law to calculate enthalpy change

    temperature of water/ � C Maximum temperature of solution/ � C Initial temperature of water/ � C Minimum temperature of solution/ � C 18.0 21.0 18.0 16.0 Discussion: *First the enthalpy change of the reaction in part A is calculated: (MgSO4(s)

  1. Validating Hess's law

    Stir and record the maximum temperature reached. Calculate the enthalpy change of this reaction in kJmol-1. Measurement of ?H?2 Pour 50cm3 of water into an empty polystyrene cup and record its temperature as accurately as you possibly can. Weigh out 2g of sodium hydroxide pellets and quickly add these to the water in your polystyrene cup.

  2. The aim of this experiment is to examine the enthalpy of combustion of the ...

    = 61K Knowing this , we can calculate the total amount of energy that has been transformed to water : Q = 40.0 g * 4.20 J g-1 K-1 * 61K Q = 10248J = 10.24 kJ Mass of Methanol used in experiment : m (CH3OH)

  1. Bomb calorimetry. The goal of this experiment was to use temperature data over ...

    By definition of enthalpy, this in the present case is enthalpy of combustion: âH = âU + â (pV) =âU + â (nRT) = âU + â ngas RT (8) âH and âU would be identical only if the pressure in the bomb remains constant.

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

    Using the thermometer, the mixture was very gently stirred for a few seconds. 8. Every five seconds, the reading on the thermometer was read as accurately as possible and noted. 9. For 120 seconds, 24 readings were taken and noted in a pre-made data collection table.

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