Lecture 12 Gases, Vapors, Solvents

Question 1

Gases

Answer 1

materials in the gaseous state at normal temperature and pressure
(NTP: 25°C, 1 atm)

Question 2

Vapor

Answer 2

Is the portion of a liquid chemical (at NTP) that is diffused or suspended in
the air

e.g., exists partially in the gaseous phase
− e.g., benzene, alcohol

Question 3

Solvents

Answer 3

are liquids in which something can be dissolved
-Inorganic: water
-organic: Hexane, tetrachloroethylene

Question 4

STP vs NTP
(standard temperature and pressure vs normal temperature and pressure)

Answer 4

-STP is used in chemistry and vapor pressure is often specified in STP (0°C (32°F), 1 atm (760 mm Hg))
-IH often uses NTP
(25°C (77°F), 1 atm (760 mm Hg))

Question 5

Volatility

Answer 5

-A substances tendency to evaporate at normal temperatures

Question 6

Vapor Pressure

Answer 6

-Describes the tendency to evaporate
-Greater VP = easier to evaporate
-VP ^ when T ^ (temperature dependent)

Question 7

Boiling point

Answer 7

-Temperature at which the VP of a liquid
equals the surrounding pressure -> liquid
changes into a vapor

Question 8

Solubility

Answer 8

-like dissolves like
-Ability of a “solute” (solid, liquid, or gaseous) to dissolve in a solvent (usually a liquid)
-> form a solution

Question 9

Properties of combustible chemicals

Answer 9

1) Flash point (lowest tempeerature)
2) Autoignition temperature (temperatures at which combustion will automatically occur= spontaneous ignition)

Question 10

Maximum equilibrium concentration (MEC)

Answer 10

the air concentration a volatile compound reaches when the evaporation reaches the equilibrium
▫ the maximum air concentration this compound can reach in the air

Question 11

Explosion (flammability) limits of combustible chemicals

Answer 11

• Lower Explosion Limit (LEL): The lowest concentration of gas or vapor that will burn in air
• Upper Explosive Limit (UEL): Highest concentration of gas or vapor that will burn in air
• The range between the LEL and UEL is known as the flammable range for a gas or vapor

Question 12

Gases that are air pollutants:

Answer 12

Carbon monoxide (CO), Carbon dioxide (CO2), Nitrogen oxides (NOx), sulfur oxides (Sox), and ozone (O3)

Question 13

How are gasses available commercially?

Answer 13

gases are available in compressed or liquefied form

Question 14

Safety and health concerns of solvents:

Answer 14

• Fire and explosion
• Spills
• Exposures - occupational, environmental, home
  o routes: inhalation, skin absorption, ingestion
• Adverse health effects after exposure
  − CNS
  − Respiratory
  − Liver
  − Kidney
  − Reproductive
  − Cancer

Question 15

Solvents and exposure limits:

Answer 15

• Exposure limits for each substance may not be exceeded, but the exposure may still be hazardous