When we think of acids and bases we tend to think of chemistry lab acids and bases like

But we are surrounded by acids and bases in the world. Most of them are weak.

Acids cause:

lemons to be sour

Acid rain to eat away at sculptures

Eat cavities in your teeth

Digest food in your stomach

Properties of an AcidTastes sourTurns litmus paper redHas a pH of less than 7Lemon juice and vinegar are good examples.

Properties of a Base Turns litmus paper blueHas a pH greater than 7Taste bitter and have a slippery feelMost hand soaps and drain cleaners are bases

What is an Acid and a Base?

ACID – pH is less than 7

BASE – pH is more than 7

NEUTRAL – pH = 7

Tea contains tannic acid

Strenuous exercise causes a buildup of lactic acid in muscle tissue

Acid rain (nitric /sulfuric acid corroding a limestone sculpture.

Carbonated soft drinks contain carbonic acid and phosphoric acid

Fruit contains citric acid

So what happens when an acid and base mix??

NEUTRALIZATION REACTION!

Acid + Base Water + Salt

i.e.) Vinegar + Baking Soda Water + Salt + Carbon dioxide

Think of the VOLCANO you made in elementary school

Another Neutralization Reaction (Alka Seltzer)

ALKA –SELTZER: made of citric acid and baking soda.

When the tablet hits water, the water acts as a solvent converting the two formerly solid reagents into liquids allowing them to react.

Reaction:Citric Acid + Baking Soda Water + Sodium citrate (salt) + CO2

C6H8O7 + NaHCO3 H2O + Na3C6H5O7 + CO2

ACID DEPOSITION

• Air pollutants (such as sulfur dioxide and nitrogen dioxide) can combine with water to form acid precipitation (rainwater that has become more acidic)

• Acid deposition is the more general term we use to describe this phenomena

• Air pollutants can come from both natural and human sources (volcanoes, forest fires, cars, factories)

Now it’s your turn…

• Use the ACID DEPOSITION handout you’ve been given and pg. 64-65 of your text to fill in the diagrams of acid deposition.

• When you are finished, complete the following questions pg. 65 # 1-3

Acids and Bases in the ENVIRONMENT

• Due to air pollution, acid rain has caused some lakes in Canada to become acidic.

• Natural limestone (CaCO3) is a base used in to neutralize lakes. This technique is called liming.

• The calcium carbonate neutralizes the acidic water, thus raising the pH of the lake water.

So what were the bad air pollutants that cause acid rain?

• Nitrogen oxide and sulfur dioxide

• The best way to reduce acid rain is to prevent it from even forming.

• So how do we reduce the amount of NO2 and SO2 in the air?

REMOVE THE SULFUR

How do you remove sulfur?

• This sulfur has been removed from sour natural gas before it is sent to consumers.

• Since sulfur emissions are one of the main causes of acid precipitation, removing the sulfur from the fuel before burning it will reduce acid precipitation

Sweet Natural Gas

Scrubbing

• Some coal also contains sulfur. When this coal is burned, the sulfurous emissions can return to Earth as acid precipitation.

• To help prevent this, a device known as a scrubber is installed on the smokestacks of many industrial plants that burn coal.

• Turn to pg. 68, and in the space below draw Figure 4.8 and describe how a scrubber removes sulfur.

Corrosion of Iron

CORROSION

• Corrosion refers to any process that chemically breaks down or degrades metal.

• The best known type of corrosion is the rusting of iron.

• Most metals will rust, but the corrosion of iron is a serious problem as this metal is widely used.

• As rust flakes off an iron structure, more metal is exposed to the environment. This weakens the structure over time and can make the structure unsafe.

4Fe(s) + 3O2(g) 2Fe2O3(s)

• What type of reaction is above?

(composition, decomposition, combustion or neutralization)

• COMPOSITION– Element + Element Compound

– Although it is not included in the chemical equation, water is also required for rusting to occur.

Solving the Problem of Corrosion

• The rusting of the steel used to reinforce concrete buildings or bridges or pipelines can cause these structures to fail.

• Repairing or replacing these structures costs millions of dollars

• So how do you prevent rusting?

1) Painting – this provides metals with a protective coating of paint.

Painting over metal prevents oxygen and water from reaching the surface of the metal. This explains why steel beams are often painted red or green.

However, once the paint chips off, water and oxygen are free to attack the steel, and rust blisters grow rapidly.

2) Galvanizing

Galvanization is a process of applying a zinc coating to iron or steel. This involves immersing the metal in a bath containing molten zinc.

This process coats the metal with a layer of zinc that provides a protective barrier between the metal and the environment.

The galvanized coating resists chipping and cracking.

3) Sacrificial Metal

Underground oil pipelines have bars of a second metal, such as magnesium, buried with the pipeline.

The magnesium will corrode but the pipeline will not. In this case, the magnesium is sacrificed in order to protect the pipeline.

It is much easier and cheaper to replace bars of magnesium rather than repair a ruptured pipeline