CHE_106_Lecture12_2009

CHE_106_Lecture12_2009 - Chemistry 106 Lecture 12 Topic:...

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

View Full Document Right Arrow Icon
Chemistry 106 Lecture 12 Topic: Thermochemistry Chapter 5.5-5.8
Background image of page 1

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

View Full DocumentRight Arrow Icon
A system absorbs heat during an __________ process. . othermic iClicker Question A. exothermic B. isothermic C. adiabatic D. endothermic
Background image of page 2
The change in enthalpy, H , is the enthalpy of the products minus the Enthalpy of Reaction (Heat of Reaction) enthalpy of the reactants: H = H products H reactants
Background image of page 3

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

View Full DocumentRight Arrow Icon
This quantity, H , is called the enthalpy of reaction , or the heat of reaction . Enthalpy of Reaction (Heat of Reaction)
Background image of page 4
Heat of Reaction Heat is denoted by the symbol q. The sign of q is positive if heat is absorbed by the system. ( endothermic ) he sign of q is egative heat is olved y The sign of q is negative if heat is evolved by the system. ( exothermic ) Heat of Reaction is the value of q required to return a system to the original temperature at the completion of a reaction.
Background image of page 5

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

View Full DocumentRight Arrow Icon
Applying Stoichiometry and Heats of Reactions Consider the reaction of methane, CH 4 , burning in the presence of oxygen at constant pressure. Given the following equation, how much heat could be obtained by the combustion of 10.0 grams CH 4 ? O(l); 2H (g) CO (g) 2O (g) CH 2 2 2 4 + + kJ -890 H o =
Background image of page 6
Thermochemical Equations How much heat could be obtained by the combustion of 10.0 grams CH 4 ? O(l); 2H (g) CO (g) 2O (g) CH 2 2 2 4 + + kJ -890 H o = 4 CH mol 1 kJ 890 16.0g 4 CH mol 1 4 CH g 10.0 - × × kJ 556 - =
Background image of page 7

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

View Full DocumentRight Arrow Icon
To see how heats of reactions are measured, we must look at the heat required to raise the temperature of a substance. This is because a thermochemical Measuring Heats of Reaction measurement is based on the relationship between heat and temperature change. The heat required to raise the temperature of a substance is its heat capacity .
Background image of page 8
Heat Capacity and Specific Heat – The heat capacity , C, of a sample of substance is the quantity of heat required to raise the temperature of the Measuring Heats of Reaction sample of substance one degree Celsius . – Changing the temperature of the sample requires heat equal to: T C q =
Background image of page 9

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

View Full DocumentRight Arrow Icon
Heat Capacity Example Suppose a piece of iron requires 6.70 J of heat to raise its temperature by one degree Celsius. The quantity of heat required to raise the temperature of the piece of iron from 25.0 ° C to 35.0 ° C is: ) C 0 . 25 C 0 . 35 ( ) C / J 70 . 6 ( T C q o o o - × = = J 0 . 67 q =
Background image of page 10
Measuring Heats of Reaction Heat capacities are also compared for one gram amounts of substances. The specific heat capacity (“specific heat”) is the heat required to raise the temperature of one am of a substance by one degree Celsius gram of a substance by one degree Celsius . To find the heat required you must multiply the
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 / 44

CHE_106_Lecture12_2009 - Chemistry 106 Lecture 12 Topic:...

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