gas laws quiz

ideal gas law equation

PV = nRT

if n, R, and T are constant

P₁V₁ = P₂V₂

if n, R, P are constant

V₁/T₁ = V₂/T₂

if P, R, T are constant

V₁/N₁ = V₂/N₂ ; doesn’t work with rigid containers

if V, R, n are constant

P₁/T₁ = P₂/T₂

if R and n are constant

(P₁V₁ ) / T₁ = (P₂V₂ ) / T₂

pressure definition

force of the atoms or molecules colliding with each other and their container

pressure conversions

1 atm = 760 mm Hg = 760 torr = 14.695 psi = 101.325 kPa

gas constant

0.0821 (needs liters, atm, mol, and kelvin)

collecting gas over water equation

P_gas = P_gas + VP_h2o

total gas pressure from components is calculated by

adding up partial pressures of each gas

partial pressure of gas equation

P_gas = (mole ratio) x P_total

be careful about MOLE RATIO and not just mass ratio

density/molar mass version of ideal gas law

d = P(mm) / RT where d = mass / volume and molar mass is mass / moles

STP and molar volume of a gas

0 degrees celsius, 1 atm, molar volume of gas is 22.4 L/mol

gas characteristics

• similar physical properties

• usually nonmetallic

• expands to fill container

• compressible

• homogeneous despite diff element proportions

vapor definition

gases that are solids/liquids at room temp

average KE for any gas is determined by the

temperature

magnitude of pressure is determined by

how hard molecules collide with walls

effusion definition

gas escaping through tiny hole

diffusion definition

spread of one substance through space or 2nd substance

relationship between effusion rate and molar mass

inversely proportional; smaller molar mass = faster molecular speed + higher probability of escaping

diffusion is slower than effusion because

molecules collide more (causes it to move in random directions)

mean free path

average path length traveled by particles between collisions; inversely proportional to pressure

order of velocity types on maxwell-boltzmann molecular speed graph

most probably, average, root-mean-squared

when changing factors in gas equations

BE VERY CAREFUL ABOUT FRACTIONS IN THE DENOMINATORS BC THEY FLIP AND EVERYTHING

for reading open closed mercury tube thing

more liquid on atmosphere side = gas has more pressure so P_gas = P_atm + Height

less liquid on atmosphere side = gas has less pressure P_gas = P_atm - Height

closed = no atmospheric pressure = P_gas = Height

for collecting gas over water

P_{inner gas} + P_h2o = P_total because youre equating the inside water level with the outside one so force from pressure inside and outside is equal

when given equation/reaction and asked for something..

use ideal gas law on gases ONLY then use stoich to convert btwn things

make sure to

standardize all units into basic ones and watch your fractions when manipulating ratios in PV=nRT

4 postulates of KMT

• gas particle size negligible relative to particle distance so gas particle volume negligible

• constant random particle motion w/ collisions

• ignored IMFs (no attractive and repulsive forces)

• temperature proportional to kinetic energy

maxwell-boltzmann distribution

• curve showing molecule number versus spped

• area under it stays constant unless adding or removing particles

gases have ideal behavior when

under high temp and low pressure

gases deviate from ideal at high pressure because

not enough space for particles to move so volume becomes significant; actual volume becomes greater than predicted

gases deviate from ideal at low temps because

particles move slowly and form IMFs so less particles and thus less wall collisions/pressure; actual pressure less than predicted

IMFs decrease

impulse of molecules hitting wall

when looking at deviations of gases look at

mass and IMFs (will need lewis structures to determine IMFs)