IX Thermodynamics B - ThermodynamicsB Thermodynamics...

Info icon This preview shows pages 1–7. Sign up to view the full content.

View Full Document Right Arrow Icon
Thermodynamics B
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Thermodynamics Deals with the interconversion of heat an other forms of energy First Law: Energy can be converted from one form to another, it can not be created or destroyed. i.e. The energy of the universe is constant. E = q + w
Image of page 2
Want to be able to predict if process or reaction will occur spontaneously (without outside interference) In many cases, spontaneous reactions are exothermic, but not always. CaCl 2 (s) Ca +2 (aq) + 2 Cl - (aq) H 2 O H = - 82.8 kJ NH 4 NO 3 (s) NH 4 + (aq) + NO 3 - (aq) H 2 O H = + 25.0 kJ So: can’t use H to determine spontaneity. New term: Entropy: (S) Entropy is a state function Entropy is a measure of the randomness or disorder of a system. The greater the disorder, the greater the entropy e.g. S(s) < S(l) << S(g)
Image of page 3

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Different from enthalpy, can have standard absolute Entropy (S o ) So: S o = S o f - S o i S o always > 0 Second Law of Thermodynamics: Entropy of the universe always increases for an irreversible process or remains constant for a reversible process. S un iverse 0 S universe = S system + S surroundings S surroundings comes primarily from change in heat energy (q at constant pressure) but also depends on the Temperature of the surroundings. S surr = Q surr T = -∆ H sys T
Image of page 4
Third Law of Thermodynamics Entropy of a pure, perfectly crystalline substance is zero at absolute zero of temperature. Why? At 0 K motion ceases, therefore, there is only one possible structure and no randomness (perfect order) S=k ln = number of arrangements k = boltzmann constant So, third law gives us Absolute Entropy
Image of page 5

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Determine if the entropy of the system: A) increases B) decreases C) stays the same 1. Benzene(s) --> benzene (l) A 2. NaNO 3 (s) --> NaNO 3 (aq) A 3. S(s) + O 2 (g) --> SO 2 (g) C 4. MgCO 3 (s) --> MgO(s) + CO 2 (g) A 5. PCl 3 (l) + Cl 2 (g) --> PCl 5 (s) B 6. 2 HgO(s) --> 2 Hg(l) + O 2 (g) A
Image of page 6
Image of page 7
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern