CH9 ppt - Chapter 9 Thermodynamics: The First Law Work/Heat...

Info iconThis preview shows pages 1–22. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 9 Thermodynamics: The First Law Work/Heat Reaction Enthalpies
Background image of page 1

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

View Full DocumentRight Arrow Icon
Combustion of Gasoline 2C 8 H 18 (l) + 25O 2 (g) 18H 2 O (l) + 16CO 2 (g) H rxn = -1.09 x 10 4 kJ 5,450 kJ of energy released per mole of octane Combustion of 1 gallon of gas 136 MJ energy
Background image of page 2
Energy: capacity to do work or to produce heat Kinetic energy: motion of object, ½ mv 2 Potential energy: due to position or composition (bonds, height of a mass) Ex. Combustion of methane (CH 4 ): potential energy stored in bonds in converted to kinetic energy (thermal energy) via heat
Background image of page 3

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

View Full DocumentRight Arrow Icon
Kinetic energy versus potential energy
Background image of page 4
CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(l) H rxn = -890 kJ
Background image of page 5

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

View Full DocumentRight Arrow Icon
CH 4 (g) + 2O 2 (g) CO 2 (g) + 2H 2 O(l) H rxn = -890 kJ
Background image of page 6
N 2 (g) + O 2 (g) + energy 2NO(g) endothermic
Background image of page 7

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

View Full DocumentRight Arrow Icon
H 2 O(s) + 6.02 kJ H 2 O(l) Melting of ice
Background image of page 8
First law of thermodynamics: The total energy of the universe is constant. Also known as “Law of Conservation of Energy”: energy is neither created nor destroyed in ordinary chemical reactions Energy in Joules
Background image of page 9

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

View Full DocumentRight Arrow Icon
A “system” Ex. System is a reaction mixture Surroundings = atmosphere around the reaction mixture
Background image of page 10
Exothermic versus Endothermic
Background image of page 11

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

View Full DocumentRight Arrow Icon
The internal energy of a system E is the sum of kinetic and potential energies of all particles. The internal energy is the capacity of a system to do work; its total store of energy. E = q + w q is heat w is work Energy: Heat + Work
Background image of page 12
Work Work: change in energy when an object is moved through a distance Example of work: compression or expansion of a gas W = -P ex V
Background image of page 13

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

View Full DocumentRight Arrow Icon
Varieties of Work
Background image of page 14
A system doing work (i.e. expansion of a gas). Work is proportional to the external pressure and change in volume.
Background image of page 15

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

View Full DocumentRight Arrow Icon
w = -P V system In (b), the gas has expanded. The system has done work (-w).
Background image of page 16
A gas in a cylinder of an engine expands by 500.0 mL against a pressure of 1.20 atm. How much work is done?
Background image of page 17

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

View Full DocumentRight Arrow Icon
Key Concepts of Thermodynamics E = q + w = heat + work w = motion against an opposing force = -P ex V exothermic: reactions that release energy as heat First Law: energy of universe is constant
Background image of page 18
A balloon is inflated by heating the air inside it. The volume changes from 4.00 x 10 6 L to 4.50 x 10 6 L by addition of 1.3 x 10 8 J of energy as heat at 1 atm. Calculate E. A car engine does 520. kJ of work and loses 220 kJ. of heat. What is the change in energy of the engine?
Background image of page 19

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

View Full DocumentRight Arrow Icon
Enthalpy Heat: q, the energy transferred (in or out) as a result of a temperature difference q = C T w here q is heat, and C is heat capacity. For chemical reactions at constant pressure, H = change in enthalpy = q (heat released or absorbed) H > 0Endothermic H < 0 Exothermic
Background image of page 20
chemical reaction? NaOH + HCl
Background image of page 21

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

View Full DocumentRight Arrow Icon
Image of page 22
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 79

CH9 ppt - Chapter 9 Thermodynamics: The First Law Work/Heat...

This preview shows document pages 1 - 22. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online