I have two questions regarding enthalpy of reactions:
1.) Care must be taken when dissolving NaOH pellets in water because the temp. can rise dramatically. Taking NaOH as system, what can be deduced about the signs of the entropy of system and surroundings?
Am I correct in saying that delta s system is< 0 and delta s surroundings is > 0?
2.)As body temp. is raised, protein structure is changed and no longer functional. Protein denaturation is this process. What can be deduced from this about enthalpy and entropy changes?
Am I correct in saying that the delta h is > 0 and the delta s is < 0?
1.) In the case of dissolving NaOH pellets in water, the temperature can rise dramatically. To deduce the signs of the entropy changes for the system and surroundings, we can consider the following:
When NaOH dissolves in water, it undergoes a exothermic reaction, which releases heat into the surroundings. The system, in this case, is the NaOH pellets.
For the system (NaOH), the entropy change (ΔS system) can be inferred as negative. This is because when the solid pellets dissolve, the randomness and disorder within the system decrease, as the ordered solid structure converts into a more disordered solution.
For the surroundings (water), the entropy change (ΔS surroundings) can be inferred as positive. This is due to the fact that the released heat from the exothermic reaction causes an increase in the disorder of water molecules as their kinetic energy and random motion increase.
Therefore, your deduction is correct: ΔS system < 0 and ΔS surroundings > 0.
2.) When the body temperature is raised significantly, proteins undergo a process called denaturation, where their structure becomes altered and they lose their functionality. To deduce the changes in enthalpy and entropy, we can consider the following:
Enthalpy (ΔH) relates to the heat absorbed or released during a reaction. In the case of protein denaturation, it involves the disruption of the protein's native structure. This process usually requires an input of energy, usually in the form of heat, to break the intermolecular forces that stabilize the protein's structure. Therefore, the change in enthalpy (ΔH) in protein denaturation is typically positive (ΔH > 0).
Entropy (ΔS) relates to the disorder or randomness of a system. Denaturation leads to a loss of the protein's native structure, resulting in a more disordered state. This implies an increase in entropy (ΔS > 0) as the molecules become less organized.
Therefore, your deduction is incorrect in this case. The correct deduction would be that ΔH is > 0 (positive) and ΔS is also > 0 (positive).