1 / 5

Thermochemical equations

Thermochemical equations. A typical chemical equation is S + O 2  SO 2 It is called a “thermochemical equation” when we add information about  H … S + O 2  SO 2  H = – 296.9 kJ If we change the equation, then the  H also changes … SO 2  S + O 2  H = + 296.9 kJ

danno
Download Presentation

Thermochemical equations

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. Thermochemical equations • A typical chemical equation is S + O2 SO2 • It is called a “thermochemical equation” when we add information about H … S + O2 SO2H = – 296.9 kJ • If we change the equation, then the H also changes … SO2 S + O2H = + 296.9 kJ • If the reaction is reversed the sign is reversed • Also, if numbers in the equation change, so will the amount of energy produced/absorbed: 2S + 2O2 2SO2H = – 593.8 kJ • Read 1st part of handout. Do Q 1-3

  2. C + O2 393.5 kJ CO2 2HI H2 + I2 53.2 kJ Answers Q1 C + O2 CO2H = – 393.5 kJ Q2 H2 + I2 2HIH = +53.2 kJ Q3 1/2H2 + 1/2I2 HIH = +26.6 kJ

  3. Answers pg. 175, Q 5.45-5.50 5.45 - At STP (25°C and 1 atm) 5.46 - The H° value 5.47 - Moles. (You can’t have 1/2 an atom) 5.48 - answer in back of book 4Al(s) + Fe2O3(s)  2Al2O3(s) + 4Fe(s) H° = -1708 kJ

  4. Answers pg. 175, Q 5.45-5.50 5.49 - If 2 = 6542 kJ then 1.5 = 4907 kJ (6542/2 x 1.5) Actually, it should be -4907 kJ since it is exothermic 5.50 - 10CaO(s) + 10H2O(l)  10Ca(OH)2(s) H° = -653 kJ Equation is reversed, thus H° sign changes Equation is multiplied by 10, thus so is H°

  5. Standard heats of reaction 5.45 ° indicates 1 atm (and is usually associated with a temperature of 25°C) 5.46 An energy term is added (e.g. H or H°) 5.47 Moles 5.48 Al(s) + 1/2Fe2O3 (s)Fe(s) + 1/2Al2O3 (s) H°= – 426.9 kJ 4Al(s) + 2Fe2O3(s)  4Fe(s) + 2Al2O3 (s) H° = – 1708 kJ 5.49 1.5 is 3/4 of 2. 3/4 of 6542 kJ is 4906.5 kJ 5.50 10CaO(s) + 10H2O(l) 10Ca(OH)2(s) H°=–653kJ For more lessons, visit www.chalkbored.com

More Related