che 112 kotz n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
CHE 112 (KOTZ) PowerPoint Presentation
Download Presentation
CHE 112 (KOTZ)

Loading in 2 Seconds...

play fullscreen
1 / 19

CHE 112 (KOTZ) - PowerPoint PPT Presentation


  • 153 Views
  • Uploaded on

CHE 112 (KOTZ). Chapter 5 Energy & Chemical Reactions. Che 112 Course Introduction. Prerequisites Course Policy and Grading Homework Shopping List Lab Start up. Chapter 5 Overview. Energy, work and heat 1 st Law of Thermodynamics Enthalpy, H. Energy and Heat.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'CHE 112 (KOTZ)' - lovey


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.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
che 112 kotz

CHE 112 (KOTZ)

Chapter 5

Energy & Chemical Reactions

che 112 course introduction
Che 112 Course Introduction
  • Prerequisites
  • Course Policy and Grading
  • Homework
  • Shopping List
  • Lab Start up
chapter 5 overview
Chapter 5 Overview
  • Energy, work and heat
  • 1st Law of Thermodynamics
  • Enthalpy, H
energy and heat
Energy and Heat

Definitions:Energy is the capacity to do work or transfer heat.

Heat is the form of energy that flows between 2 objects because of their difference in temperature.

  • KE = ½ m v 2

examples

  • PE (composition or location)examples
  • KE ↔PE interconvertedLAW OF CONSERVATION OF ENERGY
energy units
Energy Units

1 calorie DEFINED

1000 cal = 1 kilocalorie = 1 kcal

1 kcal = 1 Calorie (a food “calorie”)

But we use the unit called the JOULE

1 cal = exactly 4.184 joules

systems
Systems
  • System vs surroundings
  • Three types of systems open -

closed - isolated –

specific heat capacity c
Specific Heat Capacity, C
  • C = q / m ΔT mass dependent
  • Algebra q = ?

know: specific C H2O(l) = 4.18 J/g 0C or 1 cal /g 0C(can use Celsius or Kelvin; ΔT is same)

lab determination of specific c of a metal
Lab Determination of Specific C of a Metal
  • Assume isolated system
  • Thermal equilibrium

or q metal = - q waterNB: textbook & lab manual do not agree!!specific heat capacity = specific heat C textbook = SH manual textbook uses K; manual uses 0C

See problem #17 page 243

heating curves review
Heating Curves, review
  • Heat of fusion, ∆Hffor water 80 cal/g
  • Heat of vaporization, ∆Hvapfor water 540 cal/g
  • See other values Appendix D (table 12) See Heating Curve for water p. 219
internal energy u
Internal Energy, U
  • U defined: total energy withinsystem KE and PE molecular motion, KE

bonding, PE

  • Heat, “q” transferred energy (joules)
  • Work, w = - P Δ V
  • State functions
1 st law u q w
1st Law Δ U = q + w

Sign Conventions [see summary table p. 224]

+ energy absorbed by system; U increases when:q > 0 Endo

w > 0 compression

- energy lost by system; U decreases when:q < 0 Exo w< 0 expansion

NOTES: work = f x d ( where f = ma ) work and energy have SAME units, joules!

slide12

energy transfer in

(endothermic), +q

energy transfer out

(exothermic), -q

w transfer in

(+w)

w transfer out

(-w)

SYSTEM

∆U = q + w

terms
Terms
  • Adiabatic [ thermal insulation], q =0
  • Exothermic , q < 0
  • Endothermic, q > 0
che reactions
Che Reactions
  • @ V = constant w = 0 So, ΔU = qv
  • @ P = constant ΔU = qp + w = qp - P ΔV
  • Or qp = ΔU + P ΔV
enthalpy h defined as h u pv
Enthalpy, Hdefined as H = U + PV
  • So, ΔH = ΔU + PΔV
  • Thus ΔH = qp

extensive a state function qp = ΔH, unique value ; “heat of rxn”

  • Recall, exo and endo
  • General Enthalpy Diagrams (Energy Profiles) (skip energy level diagrams-textbook)
h and stoichiometry
ΔH and Stoichiometry

Example: Given H2 + Cl2 → 2 HCl ΔHrxn = - 184 KJfind ΔHrxn if a) 12.8 g H 2 react

b) 6.25 mol. HCl form

hess law of heat summation
Hess’ Law of Heat Summation

A + B → C + D ΔH1

C + B → E + F ΔH2

___________________________________

A + 2B → D + E + F ΔHrxnΔHrxn = ΔH1 +ΔH2

You see ex.5.8 page 235

standard enthaply of formation f h 0
Standard Enthaply of FormationΔfH0
  • Define: standard state
  • “standard heat of formation”
  • ΔfH0 = 0 for elements
  • See table Appx.L ΔHrxn0 = ∑ ΔfH0prods - ∑ ΔfH0reactnts [using molar coeffs ]see ex. 5.9 page 238
end ch 5
End Ch 5
  • You may skip sec 5.8
  • Homework questions?

logoff