Gases pt 2

Boyle’s Law

Pressure and Volume have an indirect relationship at a constant TEMPERATURE

In Boyle’s Law, as pressure increases volume _

decreases (temp + moles are constant)

How to identify Boyle’s law problems?

2 pressures and 2 volumes, temperature is constant, how does pressure change when volume changes

Absolute zero

-273.15 or 0^oC

Why do we use kelvin?

Gas laws cannot have negative temperatures and Kelvin is never negative. negative temperatures would lead to negative pressure and volume, which is impossible.

Charles’ Law

Temperature and Volume have a direct relationship at a constant PRESSURE

In Charles’ Law, as volume increases temperature _

increases

How to identify Charles’ law problems?

2 volumes and 2 temperatures, pressure is constant, relationship between volume and temperature.

Gay-Lussac’s Law

Pressure and Temperature have a direct relationship at a constant VOLUME

In Gay-Lussac’s Law, as pressure increases temperature _

increases

How to identify Gay-Lussac’s law problems?

2 pressures and 2 temperatures, volume is constant (rigid container), relationship between pressure and temperature

Combined Gas law

all of them

How to identify Combined Gas law problems?

nothing is constant

Ideal Gas Law

PV=nRT

n=

mass/Molar Mass (n/M)

Density

MP/RT or m/V

Why do gases at Low Temperatures show non-ideal behavior?

Particles slow down and attractive forces which were negligibly small now become significant

Why do gases at High Pressures show non-ideal Behavior?

Particles move closer together and become a significant portion of the total volume of a gas (opposed to just the volume of the container)

How does the Polarity of Particles Affect Ideal Behavior?

Polar gas molecules (water) have stronger attractive forces than nonpolar gases (helium) so water shows less ideal behavior than helium.

How does the size of Particles Affect Ideal Behavior?

Larger nonpolar molecules (butane - C₄H₁₀) occupy more volume than an equal number of smaller gas particles (helium) so butane shows less ideal behavior than helium.

Avogadro’s Principle

Equal volumes of gases contain equal numbers of moles at the same Temp & Pressure

1 mole of gas at STP =

22.4 L, 0^oC, 1 atm

STP

Standard Temperature (and) Pressure

When given mass or moles of A and looking for volume of B if it is at STP use..

22.4 L

When given mass or moles of A and looking for volume of B if it is not at STP use..

PV=nRT

If you are Searching for liters

start with Stoichiometry

If you have Liters

start with the Law PV=nRT