Chapter5_2 - 9/28/2011 CHEMISTRY 1307 Chapter V Principles...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
9/28/2011 1 1 CHEMISTRY 1307 Chapter V Principles of Chemical Reactivity: Energy and Chemical Reactions 2 Internal energy (U) • PE + KE = __________ (U) • Internal energy of a chemical system depends on: 1. number of particles 2. type of particles 3. temperature 3 Transferring Energy as Heat in a Physical Process CO 2 (s, -78 o C) f CO 2 (g, -78 o C) Energy transfers from surroundings to system in endothermic process.
Background image of page 1

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

View Full DocumentRight Arrow Icon
9/28/2011 2 4 Transferring Energy as Heat in a Physical Process • Gas molecules have _______ kinetic energy. • Also, _______ is done by the system in pushing aside the atmosphere. CO 2 (s, -78 o C) f CO 2 (g, -78 o C) Two things have happened! 5 Transferring Energy as Heat in a Physical Process ∆U = U(final) - U(initial) = U(gas) - U(solid) CO 2 ______ CO 2 _____ Energy 6 First Law of Thermodynamics ∆U = q + w heat energy transferred energy change work done by the system
Background image of page 2
9/28/2011 3 7 Relating U to Heat and Work •Energy cannot be created or destroyed. •From the first law of thermodynamics: When a system undergoes a physical or chemical change, the change in internal energy is given by the ______ added to or absorbed by the system plus the ________ done on or by the system: U q w   change in system energy = heat lost or gained by the system + work done by or on the system 8 First Law of Thermodynamics The total internal energy of an isolated system is _______. The _________ is that which we are interested in. The _________ are everything in contact with the system. Together: System + Surroundings = Universe •Energy of the universes (system + surroundings) is constant. 9 First Law of Thermodynamics U system = U final U initial Any energy lost by the system is transferred to the surroundings and vice versa. Any change in energy is related to the ______ and ______ states of the system. The same holds for the surrounding! Energy Energy
Background image of page 3

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

View Full DocumentRight Arrow Icon
9/28/2011 4 10 First Law of Thermodynamics energy transfer out (_________), -q energy transfer in (________), +q w transfer ___ (+w) w transfer _____ (-w) SYSTEM ∆U = q + w 11 First Law of Thermodynamics U initial U Final energy q in work in U f > U i U system > 0 (+) q out work out U f < U i U system < 0 (–) U Final U initial Energy in Energy out Heat Work U system = 0 work and heat can balance! 12 Enthalpy Most chemical reactions occur at constant P, so and so ∆U = ∆H + w (and w is usually small) ∆H = energy transferred as heat at constant P ≈ ∆U ∆H = change in ___________ of the system ∆H = H final - H initial Heat transferred at constant P = q p q p = ∆H where H = ________
Background image of page 4
9/28/2011 5 13 Enthalpy If H final < H initial then ∆H is negative
Background image of page 5

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

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 13

Chapter5_2 - 9/28/2011 CHEMISTRY 1307 Chapter V Principles...

This preview shows document pages 1 - 6. Sign up to view the full document.

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