Chemistry - Gas Laws, Thermodynamics

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48 Terms

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Charasteristics of Gas
Volume, Pressure, Temperature
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Units for volume
Litres - L (si unit)
dm^3 - decimeter cubed (convenient and used used in IB)
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Units for temperature
C - degrees celsius
K - kelvin
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Celsius to Kelvin formula
K = C + 273.15
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What is the lowest temperature possible in K
0 K: absolute zero
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Pressure
The force applied over an area (m^2)
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Units for pressure
N/m^2
Pa - pascal
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Converting pressure units
1\.0 atm = 101325 Pa = 101.325 kPa = 1.01325 bar = 760 torr = 760 mmHg = 14.6959 psi
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mmHg
Mercury
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Standard Temperature and Pressure (STP)
"Standard" set of conditions
exactly 273 kPa and 100. kPa
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Standard Ambient Temperature and Pressure (SATP)
exactly 298 K and 100 kPa
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Gas Laws
- As pressure increases, volume decreases
- As temperature increases, volume increases
- As temperature decreases, pressure decreases
- As temperature increases, pressure increases
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As pressure increases, volume decreases
P ∝ 1/V
PV = constant
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As temperature increases, volume increases
T ∝ V
T/V = constant
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As temperature decreases, pressure decreases
As temperature increases, pressure increases
P ∝ T
P/T = constant
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Boyle's Law
P1V1=P2V2 @ Constant T
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Charlses' law
V1/T1 = V2/T2 @ Constant P
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Gay Lussac's Law
P1/T1 = P2/T2 @ Constant V
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Combined Gas Laws
P1V1/T1=P2V2/T2 @ constant mols
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Units for gas laws
T - always use Kelvin
P, V - units do not matter as long as the units are the same on both sides
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Avogadro's Law
As you add additional gas to a system, the volume of that gas will increase
- temperature and pressure are held constant

n ∝ V
V1/n1 = V2/n2
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Ideal Gases + model for the behaviour of gases
I) The volume of gas particles themselves are negligable compared to the volume of the gas
II) There are no attractive forces between the gas particles
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Ideal Gas Law formula
PV = nRT
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R
Ideal gas constant (in units J/k * mol)
Volume in Ideal Gas Law formula must be in m^3, pressure in Pa, and temperature in K
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Thermodynamics
The study of how heat works
energy + temperature relate to each other
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1st Law of Thermodynamics - Conservation of Energy
- energy cannot be created or destroyed
- you can only *transfer* energy
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Heat
A form of energy
Thermal energy
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Kinetic Energy
the energy of motion
Kinetic Energy - 1/2m(^2)
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m
mass
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V
velocity
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Temperature (energetics)
a measure of the average kinetic energy
- energy is added to substance -> internal energy goes up -> particles have more kinetic energy -> particles move faster -> higher temperature
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Boltzmann Distribution
knowt flashcard image
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Potential Energy
energy that is stored in a system
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Enthalpy (H)
total internal energy of a system
- stored in the bonds
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ΔH (delta H)
change in Enthalpy

ΔH = Hproducts - Hreactants
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Endothermic
- total internal energy goes up (increases)
- absorbs heat
- ΔH is positive
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Exothermic
- total internal energy does down (decreases)
- releases heat
- ΔH is negative
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Endothermic reaction
knowt flashcard image
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Exothermic reaction
knowt flashcard image
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Measuring Enthalpy - Heat Capacity calorimetry
the science or act of measuring changes in state variables of a body for the purpose of deriving the heat transfer associated with changes of its state due, for example, to chemical reactions, physical changes, or phase transitions under specified constraints (google)
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Calorimetry equation
q = CpmΔT
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q
Heat energy (J - energy measured in joules)
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Cp
Heat capacity (J/g*K)
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ΔT
Change in temperature (K, C)
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ΔH
change in enthalpy
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Average Bond Enthalpy
The energy needed to break 1 mole of a bond of a gaseous molecule averaged over similar compounds
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Stability in reactions
The products are more stable than the reactants, as they have a lower energy level, making it easier to maintain
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Hess’s Law
The enthalpy change for a reaction that is carried out in a series of steps is equal to the sum of the enthalpy changes for the individual steps