Physical chemistry Test 1

F*dl

kg m^2/s^2

.5 mu^2

w = E_kf-E_ki

Energy posessed by a body by virtue of being in mostion

Energy posessed by a body by virtue of position

A specific segmentof hte world with deffinite boundaries on which we focus our attention

The part of the world immediately surrounding a system

System and its surroundings

Can transfer heat and material

Can only transfer heat

Can transfer neither heat nor matter

Not a function of quantity

Directly a function of quantity

An equation that describes the condition of a system as a function of intensive properties

The systems variables of state are not changing with respect to time

The kinetic energy of molecualr motion

• If A and B are in thermal equilibrium
• And B and C are in thermal Equilibrium
• Then A and C are in thermal Equilibrium

Applies under Isothermic Conditrions. If temperature and nubmer of mols are held constant then PV=Constant

Temperature is held constant

Pressure is held constant

If Pressure and mols are fixed then V/T =Constant

mass

Molar Mass

PV=nRT

• 1) gas is assumed to be composed of individual particles whose actual dimensions are small in comparison to the distance between them.
• 2) These particles are in constant motion and therefore have kinetic energy.
• 3) Neither attractive nor repulsive forces exist between the particles.

Number of molecules present

P=

e=.

Pressure exerted by a single component of a gas mixture. Defined by molar fraction* pressure total

R

• How many collisions pe second does a molecule experieince
• units : 1/s

• How many colisions per unit of second per volume occur?

• How far a molecule travels before a collision
• distnace

Most probable velocity. Peak of maxwell curve

• Compression factor
• =

Repulsive forces dominate (b term from nonideal gas)

Attractive forces dominate (a term)

Uses a to account for attraction and b to account for repulsion

No change in Heat (Q)

Normalization factor:

• Boltzman distribution:
• Incremental volume:

• )
• Maps likely distribution of particle velocities

• 4\
• Accoutns for incremental volume in maxwell distribution sphere

• NOrmalizes maxwell distribution by total molecules likely to be present

• Average speed of a molecule in system given by maxwell normalization factor. Actually less common than
• Formula:

Least common of the important speeds in maxwell distribution, this is the root mean square speed.

• e==.5mu²
• This is a function primarilly of temperature.

• Internal energy: the internal energy of a molecule is the sum of its heat and work
• u=q+w

Energy can neither be created nor destroyed. Only moved.

Pressure, Temperature, Volume, Mass, Enegy

The macroscopic properties that define a substance

The other two are then known

A path dependent function is dependent on how one reaches a point. Using a mountain analogy: Height to reach a point is always constant, distance is a function of the route you take to reach tehat point.

No. They are not. It is part of what makes them state functions.

Points at which without an external operator acting, a system will hold in a steady state over time.

The mechanical properties, chemical properties and temperature throughout a system must be uniform for something to be in an equilibrium state

If a system is changed slowly enough to maintain an equilibrium state, it is considered a reversible process.

If a system absorbs heat, q is positive. If a system loses heat, q is negative

• If work is done on a system (work flows in), then w is positive
• If work is done by a system (work flows out), then w is negative.

• Heat of system. function ot work and internal energy
• q=

Its change. We do not know how much internal energy a system posesses, only how much it changes over time

Path properties. They are dependent entirely on path and not functions of state. they are inexact integrals.

• 1) kinetic energy of motion of hte individual molecules
• 2) Potential eneryg that arise form interactions between molecules
• 3) Kinetic and potential energy of nuclei and elctorns with inthe individual molecules.

• Chemical: energy of breaking chemical bonds
• Elctrical: Work performed by current
• Mechanical : Gross work of physical motion of masses
• Osmotic: Transportation and concentration of chemicals

A force over distance. IE ENERGY

w_rev=-\

• Note that if P is not constant, we must deffine it as a function of volume before doing this calculation.
• Note that dv implies an infintessimal volume change.

• If a process is reversible, it requires more work to do because pressure is assumed constant constant and graph of change is curved.
• If a process is irreversible, then less work is required as both pressure and volume are assuemd to change. Graph is straight drop of pressure and the straight change of volume.

• We assume inc U to be constant.
• With this as a given and the realization that
• there will be more heat generated by irreversible work because there is less actual work done.

• Irreversible work is assumed to happen suddenly. Too suddenly to be considered incremental. As such, we use the final pressure to calcualte
• w_irr=-P₂(V_final-V_initial)

When a process is reversible.

It is only a function of change of heat as volume is 'fixed'

Constant volume

• Enthalpy is a state function equal to :
• H= U + PV = internal energy + PRessure * Volume
• This deffinition is only valid if all work is PV work.

inc

• One in which q and w are positive.
• This implies that heat and work flow into system.
• This also implies that the surroundings will lose heat and feel colder.

One in which q and w are negative.This implies that heat and work flow out of the system. This also implies that the surroundings will gain heat and feel hotter in temperature.

• Isochoric: Constant Volume
• Isobaric: Constant Pressure

Heat capacity is not a state function. It fluctuates fased on sate functions and as suc hwe need to account for environmental conditions.

• This is isochoric heat capacity. It implies that there is a constant volume in system. In general, it is less like lab work/real systems.
• Due to the lack of change in volume, we asusme this to be purely a function of intenral energy
• Its formula is: C_v=

• This is Isobaric heat capacity. While pressure is constant, volume may vary and we thus may need to account for work. As such it is a function of Enthalpy (H) and is far more common in the lab.
• C_p = \gr

How much heat energy (Joules) a kilogram of a substance must absorb to increase by 1 K in temperature.

It varies with temperature and type of system.

C_pm =C_vm +R

When working with an ideal gas, either form of heat capacity is equally valid.

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