Honors Chemistryadditional Notes on Gasesname ______
Honors ChemistryAdditional Notes on GasesName ______
This packet of notes will serve as additional material not found in the text related to knowledge you should have about some representative gases. All material presented will be on a quiz at a later date. You should be familiar with all equations, written or not. You should also be able to draw dot structures of all molecules discussed in these notes.
Section 1 - Oxygen and Ozone
Oxygen occurs in nature as:
O2Oxygen
These two versions are known as “allotropes”
allotropy - existence of an element in two or more forms
O3Ozone
never just as O atoms
Oxygen makes up 50% of the mass of the earth’s crust, water and atmosphere. The atmosphere is 20% by volume composed of diatomic oxygen.
Oxygen is important because it is necessary for aerobic respiration and combustion.
Properties of Oxygen
Colorless, odorless, tasteless gas
If cooled below -183 C0, it becomes a pale blue liquid
One of the most active elements (combines with most other elements)
Usually forms Oxides (where O has a - 2 charge) or ex - Na2O
Peroxides ( where 2 “O” atoms combine to have a -2 charge) orex - HOOH
Super oxides ( where 2 “O” atoms combine to have a - 1 charge)ex - RbO2
Preparation of Oxygen
1. Thermal decomposition of oxygen containing compounds
NaClO3 yields (see previous lab, types of reactions)
Mercury (II) Oxide yields Mercury and Oxygen
2. Electrolysis of Water
When water has electricity passed though it, it can be split into
2 parts hydrogen for every one part oxygen
3. Liquification of Air - Air is cooled to -200 degrees C, where both the nitrogen and oxygen become liquids. When heated, the nitrogen “boils off” ( bp = - 196 C0) leaving oxygen behind, which doesn’t boil until it reaches - 183 degrees C.
Formation and Properties of Ozone
(electricity)
3 O2 Yields2 O3
(or UV rays)
Ozone is a very poisonous , light blue gas ( smells like ozone near a copy machine and after a thunderstorm)
Ozone in the upper atmosphere absorbs UV radiation form the sun
Hydrogen
Hydrogen is the first, lightest, and simplest element on the periodic table. It represents 90% of the atoms in the universe. There is almost no “free” hydrogen on earth ( free means in its diatomic form). Most of it is contained in the water on this planet.
Liquid hydrogen is used to fuel the space shuttle. It makes up most of the matter on stars. A good quantity of hydrogen is tied up in oil and wood on this planet. It would be great to heat homes if it weren’t for its explosive capabilities. This is also a strike against it for use in automobiles.
Properties of Hydrogen
Colorless, odorless, tasteless. If cooled below - 253 C0, it liquefies.
Because of its electronegativity is in the middle of the scale ( 2.1 ), it can react with both metals and nonmetals.
Ionic HydridesM+H2yieldsMH
2 Na+H2yields 2NaH
Covalent HydridesX+H2yieldsHX
Cl2+H2yields 2 HCl
(Please note that this is different than oxygen, as Oxygen is always negative, while Hydrogen can be + or - in charge)
Preparation of Hydrogen
1. From active metals reacting with acids
Mg + 2 HClyieldsMgCl2+H2
2. Electrolysis of Water - see previous section
3. Decomposition of hydrocarbons ( petroleum )
CxHy+ H2O (g) yields CO (g)+H2 (g)
(This is the commercial method of production)
Nitrogen and Ammonia
Nitrogen is the major component (80% by volume) of the earth’s atmosphere. It is essential to all living things, but not in its diatomic form. Nitrogen makes up DNA, amino acids, and therefore, proteins. Compounds containing nitrogen are what living things need and the most important one is ammonia (NH3).
Ammonia (g) is prepared through the synthesis of nitrogen and hydrogen using iron oxide as a catalyst in a reaction chamber requiring very high heat and extreme pressure. This reaction is known as the Haber process. Fritz Haber (Germany) created the process during WW I, as the British had set up a naval blockade preventing the arrival of nitrates from Chile that were to be used to manufacture ammonia, and eventually bombs. Haber created the process, making him quite the hero to his nation. Unfortunately, the rise of anti-Semitism in the 1930’s forced him to leave his homeland only to die of a broken heart in England a short time later. The Nazi’s didn’t do themselves much good during WW II as they forced out many brilliant scientists because they were Jewish. It was part of their undoing, as many of these Jewish scientists aided America in creating the first atomic bomb.
Properties of Nitrogen
Colorless, odorless, tasteless gas. It condenses to a liquid at - 196 degrees C.
Since it is triple bonded in its diatomic form, it is:
1. very unreactive
2. requires a lot of energy to pull apart. This energy is then “stored up” in its resulting compounds. As a result, nitrogen containing compounds tend to be unstable, and therefore often explosive.
Uses and preparation of Nitrogen
Uses - The main use of nitrogen lies in the fact that it is so unreactive. Many foods are packaged in nitrogen ( not air as it contains very reactive oxygen). Also used in aerosol cans ( replacing CFC’s )
Preparation
Heating nitrogen containing compounds
ammonium nitrite when heated yields nitrogen and water
Liquefying air (see previous section)
Carbon Monoxide and Carbon Dioxide
CO2 is linear, nonpolar, much heavier than air and collects in low places.
It sublimes. The solid form is known as dry ice.
Carbon (IV) Oxide is very stable and does not burn - used in fire extinguishers - especially good for electrical fires (stupid question - why not use water on elec. fires?)
Carbon dioxide dissolves in water (CO2 + H2O yields H2CO3 {carbonic acid} ) resulting in acidic carbonated beverages (wouldn’t a Pepsi be great right now with all of this dry reading?). Carbon dioxide also is produced during baking by yeast making dough rise.
Carbon (II) Oxide (Carbon Monoxide) is a naturally produced substance found in nature, but most of the CO found in the atmosphere is man made. About 90% of that is produced by incomplete combustion from automobiles.