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SPECIFIC HEAT
CAPACITY HELP
Allows for the prediction of liquid heat capacities of a compound
at 20 Degrees Celsius . The prediction is based upon the group
contributions of each individual component of the compound.
Chemical Data >
Pred. Of liquid Heat Cap. Calculations
Method Of Use :
Determine the chemical groups of the compound which the heat
capacity needs to be determined for.
Select the contribution value of each group by selecting relevant
group structure buttons. I.e. if the compound contains alkane groups
click the Alkane/Oelfin/Alkyne button.
Once the button is selected a form will be displayed showing all
the groups available. For each group enter the number of times it
appears in the compound, in the associated text box .i.e. if the
compound has two methyl groups enter a 2 in the associated text box.
Click the okay button of each form to enter the contribution value of
the groups for the compound.
For the Extra contribution value follow these rules to calculate
its value :
Add an extra contribution value of 18.84 for any carbon group
which fulfils the following criterion :
A carbon group which is joined by a single bond to a carbon group
connected by a double or triple bond with a third carbon group.
A value of 18.84 should be added each time the above criterion is
fulfil.
Exceptions to the rule are :
For --CH3 groups no extra value is required
For a --CH2-- group fulfilling the 18.84 addition add 10.47
instead of 18.84, but, when the ---CH2-- group fulfils the addition
criterion in more than one way, the addition should be 10.47 the
first time and 18.84 for each further addition.
For any carbon group in a ring no such extra addition is
required for such groups.
Once all the contributions have been entered, enter the molecular
weight of the compound and then click the Calculate button. The
predicted Specific heat capacity value for the compound will be
calculated.
Example : compound : chlorobutadiene
Structure : CH2 = C – CH = CH2
CI
Group Contribution No. of
groups Extra Contr. Total
=CH2 21.77 2 43.54
=C-- 15.91 1 18.84 34.75
=
CH 21.35 1 18.84 40.19
--CI 36.01 1 36.01
Total Contribution 154.49
KJ/Kmol oC
Mol. Weight of compound = 88.5
Hence predicted Specific heat capacity
= 154.49/88.4 KJ/Kg oC
Below is an example of the structure forms where the information
about the components structure is entered into. Once the Okay button
is pressed the information is placed to the Pred. Of Liquid Heat Cap.
form.:-
