Chem S2 Chapter 1

Chem S2 Chapter 1

Manometer

used to measure pressure of an enclosed gas attached to a u-tube filled with mercury and open on one end

how to find gas pressure

Pgas = Patm - change H or + change H

What did Boyle study

relationship between P and V

P and V are….

inversely related

What is held constant for Boyle’s law

moles of gas and temperature

Boyle’s law is

P1V1=P2V2

Charles’s law

V1/T1=V2/T2

V and T are…

directly related

What is held constant for Charles’s law

P and moles of gas

Gay Lussac’s law

P1/T1=P2/T2

P and T in kelvin are…

directly related

What is held constant in the Gay law

moles of gas and V

Combined gas law

P1V1/T1=P2V2/T2

When to use these laws

When given 3 variables from the equation and need to find the fourth

When do ideal gas conditions occur

High T low P

Ideal gas law assumptions

1. gas particles occupy no volume

2. no attractive forces exist between gas particles (elastic collisions)

Going against the ideal gas law conditions,…

real gases do have a bit of volume and attraction to each other

Ideal Gas law

PV=nRT

What is R

the ideal gas constant (variable)

You can use the Ideal gas law to calculate

molar mass (n)

you can also use this equation to calculate molar mass too

Kitty cat equation (dRT/P) (d=density)

Vapor

the gaseous portion of a substance present above the liquid phase of that substance

Vapor pressure

pressure exerted by vapor

Substances that are volatile (evaporate readily)…

have high vapor pressures

Substances with strong intermolecular forces…

have low vapor pressures

Why do substances with strong IM forces have low Vapor pressures

it takes more energy to overcome attraction and become gas

Substances with weak intermolecular forces…

have high vapor pressures

Why do substances with weak IM forces have high Vapor pressures

it takes less energy to overcome attraction and become gas

vapor pressure ____ with ____ temperature

increases, increasing

vapor pressure _____ with _____ ____ structures

decreases, more complex

Boiling point

temperature at which the vapor pressure of a substance equals to atmospheric pressure above it

Normal boiling point

occurs at sea level

elevation _____, atmospheric pressure _______

increases, decreases

Kinetic molecular theory

1. solid particles only vibrate in place, tightly packed

2. liquid particles have some space between them and slide over each other

3. gas particles are free to move and far apart

assume that gas particle collisions are….

elastic (no energy lost)

assume that particles in a gas sample….

are very small and occupy nearly no volume

gas pressure is the result when…

gas particles collide with the surface of their container

As temperature ______, kinetic energy ______

increases, increases

diffusion

gas particles travel from high concentration to low concentration

distance traveled by gas 1/distance traveled by gas 2 =

square root of (molar mass gas 2 / molar mass gas 1)

Kinetic energy depends on…

mass and velocity

at any temperature,

gas particles have the same average KE

Average KE is _______ related to temperature

directly

Average velocity of gas particle (root mean square velocity)

Square root of (3RT/molarmass in kg)

as mass of a particle ________, average velocity ________

increases, decreases

as the temperature of a gas sample _____, the average velocity ______

increases, increases

mean free path

avg distance a particle travels between collisions in a sample of gas

I joule =

1 kg x m2s2

Effusion

gas particle escaping through a small hole into an evacuated chamber

rate of effusion for gas 1/rate of effusion for gas 2 =

square root of (molar mass gas 2 / molar mass gas 1)

Van der Waals correction factors

A- pressure, B- volume

pressure ______, deviation from ideal gas behavior _______

increases, increases

as temperature _______, gases behave _______

decreases, les ideally