1 / 21

I Am The Law!

I Am The Law!. Provide definitions of the 2 nd Law of Thermodynamics: Firstly, in words Secondly, as an equation. Spontaneous or Not?. Which of the following processes would be spontaneous ? Ice melting at -5  C and 1 atm Dissolution of sugar in hot tea

blair-bell
Download Presentation

I Am The Law!

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. I Am The Law! • Provide definitions of the 2nd Law of Thermodynamics: • Firstly, in words • Secondly, as an equation

  2. Spontaneous or Not? • Which of the following processes would be spontaneous? • Ice melting at -5 C and 1 atm • Dissolution of sugar in hot tea • Alignment of iron filings in a magnetic field

  3. S • Which of the following reactions has a S of greater than zero? • C2H4(g) + H2(g)  C2H6(g) • Be(OH)2(s)  BeO(s)A + H2(g) • N2O4(g)  2NO2(g) • Ag+(aq) + Cl-(aq)  AgCl(s)

  4. Ksp If aqueous solutions of 2.5x10-3 M Ca(NO3)2 and 1.0x10-3 M KOH were mixed together, would a precipitate form? Ksp (Ca(OH)2) = 6.5x10-6

  5. Spontaneity again… • Which of the following would be spontaneous at all temperatures? • H = -25 kJ/mol; S = -27 J/K.mol • H = +33 kJ/mol; S = -310 J/K.mol • S = +122 kJ/mol; H = +12.2 J/K.mol • S = +72 kJ/mol; H = -54.8 J/K.mol Bonus: Which would be spontaneous only at high temperatures?

  6. Gibbs Free Energy Change • What does it mean when a reaction has a G < 0 ? • What does it mean when a reaction has a G > 0? • What does it mean when a reaction has a G = 0?

  7. It’s just so common… What is the common ion effect? Give one example of this phenomenon.

  8. Michael Buffer(s) • Which of the following would not be a • good acid/base pair for use as a buffer? • HCl and NaCl • HC2H3O2 and NaC2H3O2 • HF and NaCl • NH3 and NH4Br • HC2H3O2 and KNO2 Bonus: What is Michael Buffer’s famous catchphrase?

  9. Solubility • Which of the following compounds is the least water-soluble? • BaCO3 (Ksp = 5.0 x 10-9) • PbCl2 (Ksp = 1.7 x 10-5) • Cu(OH)2 (Ksp = 4.8 x 10-20) • CaF2 (Ksp = 3.9 x 10-11) • AgI (Ksp = 8.3 x 10-17)

  10. Titrations • What is the meaning of the equivalence point during the titration of an acid with a base? • Where is the equivalence point (in terms of pH) when a strong acidandstrong base are titrated? • What about for when a weak acid is titrated with a strong base?

  11. pH plots Sketch the shape of the curve you would expect if you were to titrate a solution of ammonia with hydrochloric acid. (if pH was on the y-axis and HCl(mL) was on the x-axis)

  12. Buffers What exactly are buffers, what are they made up of, and how do they work? Give one real-life example of an important buffered solution.

  13. Buffer pH • What is the pH of a solution containing 2.5 M HF and 3.2 M KF? • One way to calculate this is through the use of an ICE table. What is the other, quicker method? What other information do you need to calculate the pH this way?

  14. And More Buffer pH • What would be the pH of the solution from the last question, if 5 g of sodium hydroxide were dissolved in it?

  15. Solubility from Ksp • Solid silver chromate (Ag2CrO4) is added to a sample of water and stirred. Analysis of the solution shows that in the solution, the silver ion concentration is 1.3x10-4 M. Assuming that the silver chromate dissociates completely in water, calculate its Ksp.

  16. Calculating S Predict the sign of S for this reaction: C2H5OH(l) + 3O2(g)  CO2(g) + 3H2O(g) Then, Using data from Appendix C in your textbook, calculate a value for S. Do your signs agree?

  17. Titration again… • 25 mL of hydrochloric acid is titrated with 0.5 M NaOH. • The solution turns pink and stays pink after the addition of 37.5 mL NaOH. • What is the significance of the color change? • What is the molarity of the HCl?

  18. Calculating G • Using the enthalpy and entropy data in Appendix C (textbook), calculate the standard free energy change for the following reaction: • 2NaHCO3(s)  Na2CO3(s) + CO2(g) + H2O(g)

  19. Solubility Equilibria • Consider the following solubility equilibria: • Zn(OH)2(s)  Zn2+ (aq) + 2OH-(aq) • Cu(OH)2(s)  Cu2+ (aq) + 2OH-(aq) • Which of the following reagents, when added to a solid mixture containing both Zn(OH)2(s) and Cu(OH)2(s), would be most effective at dissolving both solids? (a) Cu(NO3)2(aq) (b) Zn(NO3)2(aq) (c) NaOH(aq) (d) CH3CO2H (acetic acid) (e) HCl

  20. Relative entropy values • Consider the structures of diamond, graphite and buckminsterfullerene (all are different forms of elemental carbon), below: S (diamond) = 2.43 J/K.mol S (graphite) = 5.69 J/K.mol Give a possible value for the S for buckminsterfullerene… buckminsterfullerene

More Related