LC CHEMISTRY- GASES

REBECCA'S LC CHEMISTRY GASES KNOWT

Mole definition

A mole is the amount of pure substance that contains Avogadro's number (6.022×1023) of particles

Avogadro's number (number of particles in 1 mole)

6 x 10²³

Molar mass DEFINITION

the mass of one mole of a substance in grams

Diffusion

the spontaneous spreading out of a substance due to the natural movement of its particles

Temperature

a measure of the degree of hotness of an object

Convert from Celsius to Kelvin

add 273 to the Celsius value

SI unit of temperature

Kelvin

0 K

the temperature at which a gas would occupy zero volume, if it could be cooled indefinitely without becoming a liquid or a solid

SI unit of pressure

N/m² or Pascal

Normal atmospheric pressure in Pa

100,000 Pa

SI unit of volume

m³

Number of litres in 1 m³

1000 L

Standard temperature in kelvins

273 K

Standard pressure (Pa)

100,000 Pa

Boyle's Law

at constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure.

Charles' Law

at constant pressure, the volume of a fixed mass of gas is directly proportional to its temperature measured on the Kelvin scale.

Gay-Lussac's Law of Combining Volumes

when gases react together, they do so in volumes which bear a simple whole number ratio to one another and to the volumes of any gaseous products, provided the volumes are measured at the same temperature and pressure

Equation for Combined Gas Law

P₁ x V₁/T₁ = P₂ x V₂/T₂

Avogadro's Law

equal volumes of gases under the same conditions of temperature and pressure, contain equal numbers of molecules.

Molar volume in words def

The volume occupied by one mole of any gas

Molar Volume at s.t.p.

22.4 L

The 5 Assumptions of the Kinetic theory of Gases

• gases are made up of particles that are in continuous motion, colliding with each other and with the walls of the container.

• there are no attractive or repulsive forces between the molecules of a gas.

• the volume of the gas molecules is negligible compared with the spaces between them.

• when molecules collide, the collisions are perfectly elastic.

• the average kinetic energy of the molecules is proportional to the temperature in Kelvin scale.
  

2 Limitations to the Kinetic theory of Gases

• there are attractive and repulsive forces between the molecules of a gas

• volume of gas particles not negligible compared to the distances between them.

Ideal gas

a gas which obeys all the gas laws and under all conditions of temperature and pressure

Conditions at which real gases behave most like/become closest an ideal gas

• low pressure

• high temperature

Equation of State for an Ideal Gas

pV=nRT

why does ammonia gas deviate from ideal gas behaviour

strong H bonding (intermolecular forces) between molecules

why is charles law consistent with pV=nRT (state for ideal gas equation)

n and R are constant for fixed mass or gas and p also constant

Suggest a way that further deterioration of the painting1 by this chemical reaction could be prevented or delayed (chemical: malachite)

keeping it dry

give 2 reaosns why real gases (steam etc) deviate from ideal behaviour at high pressure and low temperatures

• collisions are not elastic

• intermolecular (van der waals) forces

which of the real gasses are most likely to act like an ideal gas and why?

hellium, lowest boiling point

m³ from cm³

cm³ × 10^-6

litres to m³

Litres/1000

R

8.3 JK^-1 mol^-1

n

number of moles

T

temperature in Kelvin

label this diagram

• pinhole

• aluminium foil

• boiling water

• vapour

• hotplate

• rubber band

• thermometer

describe this diagram using words

flask sealed (covered with foil) with small hole (pinhole) immersed so that at least half is underwater

Volatile liquid

a liquid with low boiling point

Relative molecular mass

average mass of a molecule compared to 1/12 of the carbon 12 isotope