ap chem ch. 5

the ideal gas law

PV = nRT

(constant) R =

• 0.0821 (L*atm)/(mol*K)

• 62.3 (L*mmHg)/(mol*K)

d (density) =

m/V = PM/RT

• my way of memorizing it: (P)rime(M)inister/(R)ight(T)

daltons law

• Ptotal = P1 + P2 +…Pn

  • were P1 is the partial pressure of gas one, P2 is the partial pressure of gas two (and so on)

• Pgas = Ptot - PH2O

  • where PH2O is the vaper pressure of water

• P1 = X1 * Ptot

  • where X1 is the mole fractio

kinetic theory (formulas)

• Etrans = 1/2 * m * u^2 = C * T

• m1u1^2 = m2u2^2

• rate2/rate1 = (M1/M2)^(1/2) = time1/time2

• u = (3RT/M)^(1/2) where R = 8.31 (g*m^2)/(s^2*mol*K)

real gases vs. ideal gases

• real gases deviate from ideal gases

  • gas molecules attract each other

  • gas molecules occupy a finite volume

• they deviate most at high pressures and low temps (smaller mean free path) and least at low pressures and high temperatures (bigger mean free path)

• deviation is so small it’s negligible

kinetic theory (theory)

• explains the effects of temperature and pressure on matter

• all matter is composed of small particle

• these particles are in constant motion

• collisions between particles are perfectly elastic (no change in total kinetic energy of the system)

mean free path

describes the average distance a molecule will travel before colliding with another molecule

what factors increase the mean free path

temperature, the number of particles in a given volume, and the mass of the given particles

pressure

• created by the force and the number of gas molecule collisions on a container wall

• pascal is the SI unit of pressure (1 Pa = 1 N/m^2)

• 101.325 kPa = 1 atm = 760 mm Hg

• nanometers and barometers are used to measure gas pressure using column of mercury

  • nanometers - open and closed arm

calculation for closed arm nanometer

gas pressure = height change

calculation for open arm nanometer

depends on which side of the mercury is the highest

boyles law

P1V1 = P2V2

charles’ law

V1/T1 = V2/T2

avogadros law

P1/n1 = P2/n2

combined gas law

(P1V1)/T1 = (P2V2)/T2