Rabu, 28 September 2011

Determine ΔH Reactions Calorimeter


Name                 : Fenton Martin
Class                  : XI A IM
No                      : 8 ( eight )
Group                : 1 ( Frist Group )
Day and Date   : Thursday, 22 September 2011
Title                   : Determine ΔH Reactions Calorimeter



 XI A IMMERSION
SMA  NEGERI  1  KROYA
        I.          Purpose             : To calculate the reactions through the trial  

     II.          Tools and Materials :
1.   Calorimeter                          : 1 pieces
2.  Themometer 100°C            : 2 pieces
3. Stirer                                     : 1 pieces
4.                        Measuring cups 50 Ml       : 2 pieces
5. A solution of NaOH 1M      :50mL
6. A solutions of HCL 1M       :50 mL

  III.          Basic Theory :
 
A thermometer is an instrument for measuring temperature.Mercury thermometers are the types of thermometers are often used by the common people. Mercury used in thermometers measure temperature because the coefficient can be calculated muainya constant so that changes in volume resulting from the increase or decrease in temperature is almost always the same. 

This device consists of a capillary tube using a glass material containing mercury at the lower end. For measurement purposes, the pipe is made in such a way that the vacuum. If the temperature increases, the mercury will expand up towards the top of the pipe and provide clues about the temperature around the measuring instrument in accordance with a scale that has been determined.
Temperature scale the most widely used worldwide is the Celsius scale with 0 points to the freezing point and boiling point 100 to point. 

Mercury thermometers were first made by Daniel G. Fahrenheit.This heat sensor equipment using materials Mercury and glass pipe with Celsius and Fahrenheit scale for measuring temperature.In 1742 Anders Celsius published a book titled "The discovery of Celsius Temperature Scale" which describes the calibration method between devices such as thermometers below: 

Place the thermometer in the water cylinder that is melting and mark the point when all the water thermometer is entirely liquid.This point is the freezing point of water. 
In the same way, mark the point when the entire thermometer boiling water completely when heated. 
For the length of the two points above the one hundred equal parts. 
Until now, three points above the calibration is still used to find the average on the Celsius scale mercury thermometer. These points can not be used as an accurate calibration method for boiling point and freezing point of water varies as the pressure difference. 

How it Works: 

Prior to the change in temperature, the volume of mercury is in the initial conditions. 
Changes in ambient temperature around the thermometer Mercury responded with volume changes. 
The volume of mercury will expand if the temperature increases and will shrink when the temperature decreases. 
The scale on the thermometer will indicate the temperature values
​​according to environmental circumstances. 

  IV.          Work Steps :
1.   Take 2 pieces measuring cups, each input into it:
v Glasses 1 : 50 mL NaOH 1 M  and measure it’s temperature ( initial temperature )
v Glasses 2 : 50 mL HCL 1 M and measure it’s temperature ( initial temperature )
2.  Pour the solution into the calorimeter, stir with a thermometer ( slowly ), while continuing to observe the temperature. Themperatures wiil rise and than be fixed and then descended. Record the temperature fixed ( final temperature ).

     V.          Observations :
Initial Temperature
Final Temperature
Temperature Changes
T HCL 1M= 27°C
T NaOH 1M = 31°C
T mean = 29°C
The temperature of the solution after the intervention
T=33°C
ΔT = T - T
= 33-29 °C
=306-302 °K
= 4  °K


  VI.          Calculation / Reaction / Discussion :

1.   Volume of the solution = volume HCL + voleme NaOH = 100 mL

2.  The density of the solution is considered equal to the density of water = 1 g/mL
Masses solutions ( m ) = volume of solution x density of water = 100 mL x 1 g/mL= 100 gr

3. Heat generated from the experiment,          
 q = m c ΔT
= 100 x 4,2 x 4 = 1680 Joule

4.                        50 mL NaOH 1 M = =  = 0,05  mol NaOH
50 mL HCL 1 M = 0,05 mol HCL

5. Based on the equation : NaOH(aq) + HCL(aq) NaCl(aq)  + H2O(I)
0,05 mol NaOH = 0,05 mol HCL = 0,05 mol H2O

6. Based on the results of the experiment ΔH reaction = -q = - 1680
For the reaction : NaOH(aq) + HCL(aq)             NaCl(aq) + H2O(I)
ΔH reaction       =
=
= - 33600 kJ
= - 33.6 kJ
Discussion :

In the lab yesterday, our group experienced a problem with the T1 (initial temperature) is not something with the standards of other groups, so we must repeat our lab so that our group can have a number of the initial temperature according to existing standards.
Over our mistakes, we apologize

Conclusion :

Of practicum in the above, we can draw the conclusion that, in seeking
ΔH we can also use the thermometer, in addition to using the formula alone.

Question :
1. How does the sign for
ΔH reaction?
2. These reactions include the reaction eksoterm
ic or endotermic?
3.          Write the thermochemical equation for the reaction!
Answers :
1.     ΔH values ​​also can be determined by the reduction of the formation enthalpy of the products minus the enthalpy of formation ofreactants. Mathematically:
.
For other reactions in general:
2.    the exothermic reaction, because liberate energy system, so the enthalpy ofthe system will be reduced, meaning that the product enthalpy is smaller than the enthalpy of reactants. Therefore, enthalpy changesare negative. So that p can be expressed as follows:
ΔH = Hp-Hr <0
3.   NaOH(aq) + HCL(aq)             NaCl(aq) + H2O(I)     ΔH = - 33.6 kJ

Bibliography
Fred Landis Microsoft Encarta Reference Library 2005 
http://en.wikipedia.org/wiki/Thermometer

                                                              Kroya, 29 September 2011
Knowing that :                                  who maker :


Pak Waryanto S.Pd.                         Fenton Martin

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