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Concept explainers
(a)
Interpretation:
The rate of heat removal to produce 300 kg/h of dry ice is to be calculated.
Concept introduction:
According to the Hess’s law, the total enthalpy for a reaction is the sum of all the changes in the multiple steps of the reaction. According to this law, enthalpy is a state function.
Specific heat capacity (Cp) of a substance is the amount of heat needed for a unit mass of substance to raise its temperature by 1∘C. It is temperature dependent and varies with temperature of the substance. The formula to calculate Cp is:
Cp(T∘C)=a+bT+cT2+dT3 .......(1)
Here, a,b,c and d are constants which is specific for a substance. The values of these constants are given in table B.2 of appendix B.
Change in specific enthalpy (ΔˆH) of any substance for the temperature change from T1∘C to T2∘C is given by:
ΔˆH=∫T2T1CpdT .......(2)
The rate of heat transfer is calculated as:
˙Q=˙nΔˆH .......(3)
(b)
Interpretation:
An expression for the rate of heat removal is to be written in terms of the heat capacities and latent heats of CO2 in different phases.
Concept introduction:
According to the Hess’s law, the total enthalpy for a reaction is the sum of all the changes in the multiple steps of the reaction. According to this law, enthalpy is a state function.
Specific heat capacity (Cp) of a substance is the amount of heat needed for a unit mass of substance to raise its temperature by 1∘C. It is temperature dependent and varies with temperature of the substance.
Change in specific enthalpy (ΔˆH) of any substance for the temperature change from T1∘C to T2∘C is given by:
ΔˆH=∫T2T1CpdT .......(2)
The rate of heat transfer is calculated as:
˙Q=˙nΔˆH .......(3)
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Chapter 8 Solutions
Elementary Principles of Chemical Processes, Binder Ready Version
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