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

We measured the change of temperature of two reactions to determine the enthalpy change of the third. We first theoretically calculated the enthalpy and then performed experiments.

Extracts from this document...

Introduction

Shazde Mehkri 11/12/08 Enthalpy change of a chemical reaction Data: Runs Initial temperature +0.1 ?C Final temperature +0.1?C Change in temperature +0.2?C 1 22.74 36.27 13.53 2 21.57 23.36 1.79 3 22.47 35.53 13.06 Final temp. is calculated by ==> Y = mx + b For reaction1: 0.00648(11)+36.2 = 36.27 (See attached graphs) (Values of m,x & b are taken from graph) Sample calculations: Run 1: Change in Temp. = Final Temp. - Initial Temp. 13.53? C = 36.27? C - 22.74??C (Similar calculation done for Run 2 and Run 3) Data processing: Reaction 1:NaOH + HCL ==> NaCl + H2O Net ionic equation: H+ + OH- ==> H2O Theoretical H for reaction 1: -(H Products - H reactants) (-286 - (-230) ...read more.

Middle

Experimental Q = mc t For run 1:reaction between NaOH and HCL NaOH + HCL ==>H2O + NaCl M=D*V D=1.03gml-1 V=100ml M=1.03*100=103 g (Uncertainty for mass is +0.5g) C=4.184 J/?C T=13.53?C Q=5830.78 j =5.830 Kj Uncertainty is +0.014j (Similar calculations done for run 2 & 3) For run 2: reaction between NaOH + NH4CL ==> NH3 + H2O Q=0.771 Kj +0.11j {Q uncertainty is calculated by [uncertainty of temp/ change in temp]} Each solution were 2.0 molar Therefore moles= 0.050 L * 2mol/1 L =. 1 mol To show Hess's law: NaOH + HCL==> H2O NH3 + H2O ==> NaOH + NH4CL {the 2 reactions equation is flipped} In order to get: NH3 + HCL==> NH4CL H for run 1=Q/mol =5.830/0.1=58.3 Kj H ...read more.

Conclusion

We then compared our theoretical values with our experimental. All of the above mentioned steps were done to prove Hess's law. Some errors existed in our experiment. The % error that we calculated was about 2.85%. These possible errors were present because of not placing the temperature probe in its right position. The temperature probe should be placed in such a way that it should be touching the solution. If we placed our probe little lower in the solution then it was we could have eliminated the chance of such error. The mass should be measured using beakers rather than calculating it manually. This is done to increase accuracy. Also, equal time should be given to all reactions in order to generate heat. For this magnetic stirrers should be rotated at constant speed for all reactions. ...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. The Enthalpy of Neutralization

    Neutralization Mass/volume of solution [Mass = Volume, if we assume 1g = 1cm3] 25.00cm3 (� 0.5cm3) + 25.00cm3 (� 0.5cm3) = 50.00cm3 (� 1.0cm3) = 50.00g (� 1.0g) Calculation for measuring enthalpy changes [Q = m�c�?T] Q = (50.00g � 1.0g)

  2. hess's law

    The error involved in this experiment is pretty high and that is the reason why there are doubts and uncertainties evolving in our minds as to consider this method or investigation appropriate or not. The original or literature value for the enthalpy change of formation of hydrated copper (II)

  1. Determining an enthalpy change of reaction

    Temperature/?C 32 32 32 32 32 32 32 31.5 Trial 1 Time/s 0 30 60 90 120 150 180* 210 240 Temperature 22.5 22.5 22.5 22.5 22.5 22.5 25 29.5 30 Time/s 270 300 330 360 390 420 450 480 ?

  2. Enthalpy Change Design Lab (6/6)How does changing the initial temperature (19C, 25C, 35C, and ...

    and KOH(aq) in a doubled polystyrene cup. Since molar enthalpy is determined through a few different values that need to be collected during the investigation, the steps taken to determine the molar enthalpy of the reaction of 1.00 mol dm-3 HCl(aq)

  1. Thermodynamics: Enthalpy of Neutralization and Calorimetry

    temperature reaches 95C�, taken off, allowed to rest until the temperature stops rising (this temperature is also recorded), and placed into the calorimeter. The metal and water are stirred for a minute and then the temperature of the water with the metal is taken again and recorded.

  2. Enthalpy and Hess law

    1 60 � 0.1 68.8 � 1 70 � 0.1 68.2 � 1 80 � 0.1 67.7 � 1 90 � 0.1 67.1 � 1 100 � 0.1 66.5 � 1 110 � 0.1 66.1 � 1 120 � 0.1 66.5 � 1 130 � 0.1 65.0 � 1 140

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

    Time ( s ) ±1 s Temperature in °C ± 1 °C Average temperature in °C ± 1 °C Trial 1 Trial 2 Trial 3 0 24.0 24.0 24.0 24.0 0 24.0 24.0 24.0 24.0 0 24.0 24.0 24.0 24.0 15 24.5 25.0 24.5 25.0 30 26.0 25.5 25.5 25.5 45 28.5 27.5 29.0

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

    it would not be possible to draw a good graph using points that are unevenly spaced apart Time interval is taken to be 5 seconds between each reading. Room temperature and pressure Conditions under which the experiments are performed should remain constant The experiments were carried out in the same room and on the same day.

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