LectureNote4

LectureNote4 - Thermochemistry (Energy Relationships in...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Thermochemistry (Energy Relationships in Chemical Reactions) Every chemical reaction obeys two fundamental laws: the law of conservation of mass and the law of conservation of energy The nature of energy and types of energy Energy is the capacity to do work Some fundamentals Force: F = ma (kg m s -2 , newton) Work = Force × Distance (kg m 2 s -2 , joule) Energy has the same units as work Energy
Background image of page 1

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

View Full DocumentRight Arrow Icon
2 Some forms of energy Kinetic (thermal) energy: energy associated with motion Potential energy: energy available by an object by virtue of its position Chemical energy: energy stored within the structural units of chemical substances Law of conservation of energy : Energy can neither be created nor destroyed. However, energy can be converted from one form to another.
Background image of page 2
3 Explosive agents Year 1870; 7580 m/s Year 1910; 6930 m/s Year 1940; 8754 m/s Year 1955; 9110 m/s cyclotetramethylene-tetranitramine (HMX) Year 1990; 9380 m/s year of introduction and detonation rate
Background image of page 3

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

View Full DocumentRight Arrow Icon
4 Energy changes in chemical reactions Some fundamentals Heat: the transfer of energy between two bodies that have different temperatures. Heat has the same units (Joule) as energy and work. Thermochemistry is the study of heat changes in chemical reactions. Some terminologies
Background image of page 4
5
Background image of page 5

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

View Full DocumentRight Arrow Icon
6
Background image of page 6
7 Some terminologies A reaction is exothermic if it gives off heat. Energy flows from the system to the surroundings . Stronger chemical bonds in products than in reactants . Less potential energy in products
Background image of page 7

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

View Full DocumentRight Arrow Icon
8 A reaction is endothermic if it takes in heat. Energy flows from the surroundings to the system . Weaker chemical bonds in products than in reactants . More potential energy in products
Background image of page 8
9 An exothermic reaction At constant pressure, the heat transfer associated with the reaction is quantified by Δ H. The sign of H is minus (-) for an exothermic process Enthalpy To quantify the heat flow of a process at constant pressure .
Background image of page 9

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

View Full DocumentRight Arrow Icon
10 An endothermic reaction The sign of Δ H is plus (+) for an endothermic process
Background image of page 10
1. Stoichiometric coefficients always refer to the number of moles of each substance. 2. Reverse the direction of a given reaction, reverse the sign of Δ H. 3. If a reaction is multipled by some factor, its
Background image of page 11

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

View Full DocumentRight Arrow Icon
Image of page 12
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 52

LectureNote4 - Thermochemistry (Energy Relationships in...

This preview shows document pages 1 - 12. Sign up to view the full document.

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