Exam 3 Flashcards by Emily Klatzer

Define pressure, which all gases have

Force pushing against a surface, F/A

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SI unit of pressure

Pascal = 1kg/ms^2 = 1n/m^2

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Device used to measure the pressure of the atmosphere

Barometer, uses mercury

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How many pascals in 1 atm

101,325 Pa

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How many millimeters of mercury in 1 atm

760 mmHg

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How many torrs in 1 atm

760 torr

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How many pounds per square inch in 1 atm

14.7 lb/in^2

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Pressure of a water barometer is proportional to

(column height)(density)

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Two types of manometers, which is more convenient

Closed end, gas pressure is measured directly versus in a open end manometer where you need to know pressure of the atmosphere

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What is Boyle’s law

Volume of a fixed volume of gas at a constant pressure is inversely proportional to the applied pressure

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Volume of a gas is in proportion to (involving pressure)

1/P

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What is Charles’s law

The volume of the gas increases linearly with temperature

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Volume of a gas is in proportion to (involving temp)

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-293.15 degrees C was deduced to be the coldest possible temp because why

A colder temp would yield a negative volume

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What is Gay-Lussac’s law

Pressure of a gas increases linearly to the Kelvin temperature when volume & moles are constant

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Pressure of a gas is in proportion to (involving temp)

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What is Avagadro’s law

The volume of a gas increase linearly to the number of moles

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Volume of a gas is in proportion to (involving moles)

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What is the universal gas constant

PV/nT

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What is the ideal gas equation

PV=nRT

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Standard temp & pressure of a gas

273.15 K at 1 atm

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1 mole of any gas at 0 degrees C & 1 atm occupies what volume

22.41 L

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R involving L*atm

.08206 Latm/molK

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R involving cal

1.987 cal/mol*K

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R involving J

8.314 J/mol*K

R involving m^3*Pa

8.314 m^3*Pa/mol*K

R involving L*torr

62.36 L*torr/mol*K

How to find molar mass of a gas

dRT/P

Formula for finding mole fraction relating pressures of gases

Pa/Pt

Pressure of gas must take into account the pressure of what

Water

The average kinetic energy of molecules in a gas are directly proportional to what

Kelvin Temp

Average KE is in proportion to

SI unit for energy

1 J = 1kg*m^2/s^2=1Nm

In the ideal gas equation, PV is equal to what

Average KE

Distribution of molecular speeds (molecular kinetic energies) set forth by

Maxewell-Boltzmann

How to find root-mean-square speed

sqrt of 3RT/M

Rates of diffusion of gases are what to the square roots of their molar masses

Inversely proportional, r1/r2=sqrt(M2/M1)

Equation that takes into account the adjustments of pressure and volume for real gases

Van der Waals

Define energy

Ability to do work

1 calorie is how many J

4.184 J

First law of thermodynamics

Law of conservation of energy

Open system

Allows for exchange of mass & energy with surroundings

Closed system

Allows for the transfer of energy but not mass with the surroundings

Isolated system

No transfer of mass or energy with surroundings

Internal energy

Total energy of a system (ΔE)

Can we measure the absolute internal energy

No, just changes

What adds together to get internal energy of a system

q (heat) + w (work)

If heat is added, q is

If heat is removed, q is

If work is done ON the system (system compressed), then w is

If work is done BY the system (system expands), then w is

Expansion of a gas against a constant pressure is referred to what

Mechanical work

Work equation for compressing/expanding a gas

W=-PΔV

In gas expansion, ΔV is

In gas compression, ΔV is

Process that gives off heat is called

Exothermic, system loses heat & surroundings gain heat

Process where heat flows from surroundings to the system

Endothermic, system gain heat & surroundings lose heat

Heat energy is called what when the system is at a constant pressure

Enthalpy (ΔH)

In an endothermic reaction, ΔH is

+, heat flows into system

In an exothermic reaction, ΔH is

-, heat flows out of system

At constant volume, there is no work done so

ΔE=q

At constant pressure, work can be done on or by the system (compression/expansion)

ΔE=q-PΔV

Relationship between ΔH and ΔE at a constant pressure

ΔH=ΔE+PΔV

Does enthalpy change depend on the physical states of substances

Yes

Is enthalpy an extensive or intensive property

Extensive

What is a calorimeter

Measures the amount of heat generated or consumed

Heat capacity (extensive property)

Amount of heat required to raise the temp of matter 1 K (heat absorbed/ΔT)

Molar heat capactiy (intensive property)

Amount of heat required to raise the temp of one mole of a substance 1 K (heat absorbed/mol*ΔT)

Specific heat (intensive property)

Amount of heat required to raise the temp of one gram of a substance 1 K (q/m*ΔT)

Constant pressure calorimeter

q=ΔH (~ΔE)

Constant volume calorimeter

q=ΔE

To calculate Δreaction using a calorimeter

q(p)=C*ΔT=ΔH

If ΔH is negative, then do products or reactants have less energy content (PE)

Products have less

Standard conditions for thermochemistry (ΔHdegree)

25 degrees C, 1 atm

State functions

Depend only on conditions, not on the process to reach said conditions

Examples of state functions

Pressure, temp, volume, chemical composition, internal energy, enthalpy

Modifying chemical reactions to get ΔH uses what

Hess's Law of heat summation

Gases with standard enthalpy change of 0 (ΔHfdegrees)

C(graphite), beer (all g except I & Br), all metals (s) (except Hg), Hg(l)

Define (ΔHfdegrees)

Standard enthalpy change for formation of a substance from the elements in their standard states

How to find ΔHdegrees of a reaction

Add up the standard heat of formation of products and subtract the standard heat of formation of the reactants

Compare ΔH and ΔE for reactions using the Δn

ΔE=ΔH-Δn(RT) or ΔE=ΔH-PΔV