thermodynamics 1 chapter 1

what is the best reaction for an air bag

2NaN3 (s) → 2Na (s) + 3N2 (g)

N2 is an inert gas

Na is reacted with KNO3 + 3iO2

small amounts of reactant required to react to produce large amounts of gas

what helps distinguish between the 3 states of matter

- distinguish by saying the physical states

- p = pressure, T = temperature

what are the properties of a solid

- molecules packed close together in a regular way
- molecules vibrate about a fixed average position
- crystalline
- ordered

what are the properties of a liquid

- molecules close together but arranged randomly

- molecules can move past each other, but there are many collisions

- has less intermolecular interactions than a solid

what are the properties of a gas

- molecules far apart

- molecules move rapidly in random directions

P h2o(s)

0.98 g cm^-3

P h2o(l)

1.00 g cm^-3

P h2o (g)

0.00075 g cm^-3

define boyle's law

pressure is inversely proportional to volume [for a constant amount of gas at constant temperature]

boyle's law in symbols

pV = constant (n [no. moles/amount of gas] and T [temp in Kelvin] are constant)

p ∝ 1/v

gas pressure law

pressure is directly proportional to temperature [for a constant amount of gas at constant volume]

p = constant x temperature [n and V are constant]

perfect gas equation of state

pV = nRT

p = pressure

V = volume

n = no. moles

T = temp in Kelvin

R = gas constant

what is R

the gas constant

R = 8.314 J K-1 mol-1

R = 0.08206 dm3 atm K-1 mol-1

SATP =

STP =

standard ambient temperature and pressure (T = 298K, p = 1x10^5 Pa)

standard temperature and pressure (T = 0.00 degrees C, p = 1.00 atm)

another form of the perfect gas equation

p1v1 / t1 = p2v2 / t2

proof of the another form of the perfect gas equation

pv = nrt

pv/t = nR [R is a constant]

if n is constant, pv/t is constant

therefore p1v1/t1 = p2v2/t2

define partial pressure

pressure gas would exert if it occupied the container on its own

define total pressure

the sum of the partial pressure

dalton's law

Ptotal = Px + Py

define mole fraction, Xa

the amount [in moles] of A as a fraction of the total amount

Xa =

nA / ntotal

what must Xa always be

< 1

Pa =

partial pressure of any gas =

Xa x Ptotal

mole fraction of gas x total pressure