1 / 20

Enthalpy

Click on buttons to go forward or back. Question mark buttons go to answers. Enthalpy. By: Veronica Mendez and Quinn Shollenberger. ONLY CLICK ON THE QUESTION MARKS AND/OR ARROW. Lost?.

gilles
Télécharger la présentation

Enthalpy

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. Click on buttons to go forward or back Question mark buttons go to answers Enthalpy By: Veronica Mendez and Quinn Shollenberger ONLY CLICK ON THE QUESTION MARKS AND/OR ARROW

  2. Lost? If at any time you are lost during the tutorial, right click and a menu should come up. Click on Go To Slide and select the slide you want or go back to the first slide.

  3. Definition • Enthalpy- the heat content of a system at constant pressure. • Enthalpy- ∆ H

  4. Equation #1 • ∆H = nCp∆T • n is moles • Cp is specific heat capacity (usually a given value) • ∆T is the change in temperature

  5. Equation #2 • ∆H =∑ ∆Hp - ∑ ∆Hr • ∑ ∆Hp is the summation of the products • ∑ ∆Hr is the summation of the reactants

  6. Example problem • Find ΔH of the reaction. • 1CH4 + 2O2 --> 1CO2 + 2H2O • Mole Ratio is 1:2:1:2 because the coefficient in front of CH4 is 1; coefficient in front of O2 is 2; coefficient in front of CO2 is 1; coefficient in front of H2O is 2.

  7. Example problem: Set up • ΔH = [∑(ΔHCO2 + ΔHH2O)] – [∑(ΔHCH4 + ΔHO2)]

  8. Example Problem: Plugging in the numbers • ΔH = [(-393.5KJ/m X 1m) + (-286KJ/m X 2m)] – [(-74.8KJ/m X 1m) + 0][(-393.5 KJ) + (-572 KJ)] –(-74.8 KJ) • ΔH = -890.7 KJ (exothermic)

  9. Example Problem: Further explanations • The numbers from the equation: ΔH = [(-393.5KJ/m X 1m) + (-286KJ/m X 2m)] – [(-74.8KJ/m X 1m) + 0][(-393.5 KJ) + (-572 KJ)] –(-74.8 KJ) can be found on any Chemistry reference source. This includes CP values.

  10. Reminder • Do not forget to cross out your moles • Be careful with positive and negative signs

  11. Quiz question 1 • Calculate ΔH at 25°C for: Na2O (s) + H2O (g) NaOH (s)

  12. Quiz question 2 • If 15.0 g of Gold is heated from 16.1°C to 49.3°C, what is the heat absorbed by the gold?

  13. Quiz question 3 • When 4.4 Kg of NaCl cools from 67.2°C to 25.0°C, how much heat is gained by the surroundings from the NaCl? (Cp NaCl 50.5 J°C-1M-1)

  14. Quiz Question 4 • Determine the standard molar heat of combustion (ΔH ) id Methanol, CH3OH, when it is burned. Use H20(g)

  15. Explanation to Quiz question 1 • Steps: • Balance equation: Na2O+H2O  2NaOH • [(- 427KJ/m)(2m)]-[(242KJ/m)(1m) + (- 415.9KJ/m)(1m)] • ΔH = -196.1KJ

  16. Explanation to Quiz question 2 • ∆H = nCp∆T • 15.0 g(1m/ 197g)= 0.07614m • (0.07614m)(25.4J/m°C)(33.2°C) • ∆H = 64.2 J

  17. Explanation to Quiz Question 3 • ∆H = nCp∆T • Convert kg into g • 4400 g (1m/58.5g) = 75.2m • (75.2m)(50.5J/m°C)(42.2 °C) • ∆H = 1.60 x 10 J

  18. Explanation to Quiz question 4 • Combustion reaction and balance the equation 2CH3OH + 3O2 2CO2 + 4H2O

  19. Explanation for Quiz question 4 cont… • [(-393.5KJ/m)(2m)+(242KJ/m)(4m)] – [0+(-239KJ/m)(2m)] • ∆H = 1277 KJ

  20. The End!!!!

More Related