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Experiment 8 enthalpy

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Experiment 8 enthalpy Powered By Docstoc
					                                                                                       1
                                                                           Cascillas Guy
                                                                              Janai Irby
                                                                       November 29, 2007


           Experiment 8: THE ENTHALPY OF CHEMICAL REACTION.

PURPOSE: The purpose of this lab is to find the specific heat capacity of a given
calorimeter and to observe the amount of heat released from three neutralization
reactions.

Procedures

-The temperature probe is calibrated by first putting it in boiling water and typing 100 in
the box titled Value under High Point to set the highest temperature. The probe is then
put in ice-water bath and in the calibration window 0 is typed in the box labeled Low
Point Value to set the lowest temperature.

-Now to determine the heat capacity of the calorimeter, first the mass of the empty
calorimeter is determined [3.593g]. Water at room temperature of known mass and
volume is poured into the calorimeter and the temperature is places in it and then the
start button is clicked. After about one minute hot water of known volume and mass is
added to the cold water already in the calorimeter while the temperature probe is still
in the solution. The graph of time to temperature is obtained and from it the final and
initial temperatures are determined.

-Measuring the enthalpy of neutralization for NaOH and HCl.
The mass of the NaOH is determined after putting it into the calorimeter. The
temperature probe is placed in the solution and after about one minute the HCl solution
is added with the probe still in the solutions. The graph of the temperature to time is
obtained and from it the final and initial temperatures are determined.

- Measuring the enthalpy of neutralization for NaOH and HN03.
The mass of the NaOH is determined after putting it into the calorimeter. The
temperature probe is placed in the solution and after about one minute the HN03
solution is added with the probe still in the solutions. The graph of the temperature to
time is obtained and from it the final and initial temperatures are determined.

- Measuring the enthalpy of neutralization for NaOH and CH3COOH.
The mass of the NaOH is determined after putting it into the calorimeter. The
temperature probe is placed in the solution and after about one minute the CH3COOH
solution is added with the probe still in the solutions. The graph of the temperature to
time is obtained and from it the final and initial temperatures are determined.

Observations:
                                                                                          2
                                                                              Cascillas Guy
                                                                                 Janai Irby
                                                                          November 29, 2007




Calculations:

Mass of calorimeter = 3.593

Volume of cold water = 20ml

Mass of calorimeter and cold water = 22.713

Mass of cold water = 19.12g

Density of cold water = 1g/ml

Mass of hot water and calorimeter = 40.826g

Mass of hot water = 37.233g

Volume of hot water = 40ml

Density of hot water = 1g/ml



        Finding the specific heat capacity of the calorimeter

C H20 * M hot *(T final – T initial(hot)) + C H20* M cold * (T final – T initial(cold) + C cal *
(T final – T initial(cold)) = 0

37.233g*4.184*(308K-319.5K) + 4.184*19.12*(308K-292.5K) + C cal*(308K-319.5K) = 0
      -1791.47 + 1240 + C cal * 15.5 = 0
      -551.47 + C cal *15.5 = 0
      C cal * 15.5 = 551.47
              C cal = 35.58 J/gK

Reaction between NaOH and HCl:

Mass of HCl and calorimeter = 25.235g

Mass of HCl= 21.642g
                                                                                    3
                                                                        Cascillas Guy
                                                                           Janai Irby
                                                                    November 29, 2007
Mass of HCl and calorimeter and NaOH = 54.794

Mass of NaOH = 29.559g

Final temperature of reaction = 51.5 degrees Celsius

Initial temperature of reaction = 29 degrees Celsius

Reaction between NaOH and HN03:

Mass of HNO3 and calorimeter = 26.613g

Mass of HNO3 = 23.02g

Mass of HNO3 and calorimeter and NaOH =54.904g

Mass of NaOH =28.291g

Final temperature of reaction =

Initial temperature of reaction =

Reaction between NaOH andCH3COOH:

Mass of CH3COOH and calorimeter = 23.495g

Mass of CH3COOH = 19.902g

Mass of CH3COOH and calorimeter and NaOH = 54.001g

Mass of NaOH = 30.506g

Final temperature of reaction = 47.5 degrees Celsius

Initial temperature of reaction = 22.5 degrees Celsius



Conclusion:

        After completing the experiment, we concluded that the specific heat capacity of
the calorimeter was 35.58 J/gK.
                                                                                         4
                                                                            Cascillas Guy
                                                                                Janai Irby
                                                                      November 29, 2007
         From observing the graphs of the neutralization reactions we noticed that the
temperature starts low but when we add the second solution there is a sharp increase in
temperature. Given time, the temperature then drops to a stable temperature but not
as low as the starting temperature. We concluded that the reaction was an exothermic
one (gives off energy to its surroundings) and the sharp change is an example of it giving
off energy. When the temperature finally drops to its resting place, we concluded that
this is when the energy is the same throughout the solutions. For one of the reactions
we could not pull up the graph on the computer to print it, but we predicted that it
would show the same results as the other graphs.

				
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