Gases

Gas properties

Neither definite shape nor volume (fits any container, exerts pressure, volume changes with T and P)

Mixes completely with other gasses

Much less dense than solids liquids

Gas pressure depends on

Num of particles in given vol

Volume of container

Avg speed of particles

Pressure formula

P = F/A

Force/unit area

1 atm > mmHg

760 mmHg

Barometer

Measures atmospheric pressure

Barometer mechanics

Atmospheric pressure increases, liquid moves up tube, decreases moves down into pool

Boyle’s Law

Volume decreases; pressure increases

P₁V₁ = P₂V₂

Charles’s law

Temperature increases, volume increases

V₁/ T₁ = V₂ / T₂

What to do when pressure drops?

Exhale

Avagadro’s Law

volume increases; moles increase

V₁/ n₁ = V₂ / n₂

Amonton's' Law (Gay-Lussacs)

temperature increases; pressure increases

P₁/ T₁ = P₂ / T₂

Combined Gas Law (if n is constant)

(P₁V₁)/T₁ = (P₂V₂)/T₂

P

pressure (in atm)

V

volume (in liters)

n

moles

T

temperature (in kelvin) °C + 273.15

R

universal gas constant

0.08206 L atm K^-1mol^-1

at STP, 1 mol of gas occupies

22.4 L

Ideal Gas Law

PV = nRT

steps for finding mass from V, P, and T

convert to correct units (ex L, K)

rearrange PV = nRT to solve for n (moles)

n = PV/RT

convert moles to grams using molar mass

steps for finding volume from reactant n, T, and P

ensure balanced equation

multiply reactant moles by ratio

rearragne PV = nRT to solve for V (L)

V = nRT/P

how to find mass of reactant from product V, T, P

ensure balanced equation

convert to correct units (L, K)

rearrange PV = nRT to solve for moles (n) of product

multiply by ratio

convert to grams using molar mass

relationship between moles and mass

molar mass = mass/moles (n = m/MM)

rearranged solving for molar mass equation

MM = mRT / PV

rearranged solving for density equation

d = P(MM) / RT

daltons law of partial pressures

P_total = P₁ + P₂ + P₃ + …

Mole Fraction

ratio of mols of component to total moles in mixture

X₁ = n₁ / n_total

relationship between moles and pressure

they are proportional

X₁ = n₁ / n_total = P₁ / P_total

mole fraction in terms of pressure equation

P₁ = X₁P_total

to find a partial pressure of a gas

convert to correct units (moles, K, L)

use rearranged PV = nRT formula P = nRT / V

answer of partial pressure in atm

finding total pressure of a sample

add all partial pressures together

solving a mole fraction

add all partial pressures for total

divide each partial pressure by the total

boom mole fraction

gas over water partial pressure only depends on…

temperature

gas collected over water finding mass

use table or provided vapor pressure to get second pressure

subtract our to find moles of of partial pressure

convert to correct units

use rearranged PV = nRT to find moles

molar mass to convert to mass