How can you predict whether the change in entropy for a system will be positive or negative? Like if the enthalpy is negative what will the entropy be?
Try these 2 sites:
http://www.shodor.org/unchem/advanced/thermo/index.html
http://en.wikipedia.org/wiki/Chemical_reaction
To predict whether the change in entropy for a system will be positive or negative, you need to consider various factors such as the physical state of the substances involved, the complexity of the molecules, and the nature of the reaction. Here are some general guidelines:
1. Physical State: In general, when a substance changes from a solid to a liquid or from a liquid to a gas, the entropy increases. Conversely, when a substance changes from a gas to a liquid or from a liquid to a solid, the entropy decreases.
2. Complexity: Generally, more complex molecules have higher entropy than simpler molecules. This is because complex molecules have more degrees of freedom and more ways to arrange themselves, leading to increased disorder.
3. Nature of the Reaction: Different types of reactions have different effects on entropy. For example:
- Dissolution reactions, where a solute is dissolved in a solvent, usually result in an increase in entropy because the dissolved particles become more randomly distributed.
- Combustion reactions, where a substance reacts with oxygen to produce carbon dioxide and water, often result in a significant increase in entropy due to the formation of multiple gaseous products.
- Reactions that result in the formation of a solid product from aqueous ions may lead to a decrease in entropy due to the decreased disorder of the system.
Regarding the relationship between enthalpy and entropy, there is no direct correlation between them. The sign of the enthalpy change (positive or negative) does not determine the sign of the entropy change. They are two independent thermodynamic properties that describe different aspects of a system.
To explore more about predicting entropy changes and understanding chemical reactions, you can visit the following resources:
1. The Shodor website (http://www.shodor.org/unchem/advanced/thermo/index.html) provides advanced topics in thermochemistry, including entropy and enthalpy changes. It offers interactive simulations that can help you grasp these concepts with hands-on experience.
2. The Wikipedia page on "Chemical reaction" (http://en.wikipedia.org/wiki/Chemical_reaction) provides a comprehensive overview of chemical reactions, including information on thermodynamics and the relationship between entropy and enthalpy. It can be a helpful resource to gain a more in-depth understanding.
Remember, predicting entropy changes accurately often requires a more detailed analysis based on the specific reaction and the conditions involved. These guidelines serve as general rules but may not be applicable in all cases.