Acids and Bases

• If you read the label on a jar of pickles or on a ketchup bottle, you would read that there is an acid or two on the list.

• Our stomachs contain acid to help digest food.

• A lot of our household cleaners contain bases.

Acids

• Acids are a group of compounds that have similar properties when dissolved in water.

• An Acid• Conducts electricity• Turns litmus from blue to red• Reacts with certain metals• Reacts with carbonates• Tastes sour

• The properties of acids result from one of the smallest particles – the hydrogen ion (H+).

• All acids release H+ ions in water

• Strong acids release more Hydrogen ions than weak acids

Uses of Acids

• Some acids are weak. • Citric acid is found in fruits, such as oranges and

grapefruits.• Phosphoric acid is found in soft drinks.• Vinegar is made up of acetic acid and water.

• Some acids are strong.• Sulfuric acid is used to make steel, plastics and

detergents.

Common AcidsName Formula Use

Hydrochloric Acid

HCl •Stomach acid•Adjusting pool acidity

Sulfuric Acid H2SO4 •Car batteries•Making detergents and cleaning steel

Phosphoric Acid

H3PO4 •Gives soft drinks a tart taste

Acetic Acid HC2H3O2 •Vinegar

Bases

• Most of the bases that you will come across are ionic compounds with a common set of properties.

• A base• Conducts electricity• Turns litmus red to blue• Tastes bitter• Feels slippery

• Bases have similar properties because they release Hydroxide ions (OH-) when dissolved in water.

• Strong bases release a lot of OH- ions in water.

• Weak bases release a little bit of hydroxide ions in water. Weak bases are safe enough to consume.

Uses of Bases

Name Formula Use

Sodium Hydroxide

NaOH •Making soap and removing grease

Magnesium Hydroxide

Mg(OH)2 •Antacid medication

Calcium Hydroxide

Ca(OH)2 •Controlling acidity in soil and pool water

Hazards of Acids and Bases

• Many common acids and bases are corrosive and will cause severe burns if they come in contact with eyes and skin.

• Car batteries contain sulfuric acid, one of the strongest and most corrosive acids. People who work with H2SO4 need to be very careful.

• Sodium hydroxide is a strong base found in some drain cleaners. It is effective in clearing blockages because it breaks down the clumps into slimy, slippery mush that flows away.

• Bases feel slippery because they are breaking down your own skin as you touch them!

• Acids and bases can damage the environment if they are not properly handled. Waste acids and bases should be taken to a waster depot for proper disposal.

The pH Scale

• One of the tasks in maintaining a pool is to keep it at the correct pH.

• Correct pH will reduce the chance that swimmers will suffer eye irritation, but will make sure that the pool is still at the right level to be disinfected.

• The pH of a solution tells us how acidic or basic that solution is. The pH scale ranges from 0 to 14.

• Extremely acid solutions, such as car battery acid, have a pH of 0.

• The most basic solutions, such as industrial strength drain cleaners, have a pH of 14.

Is a Solution Acid or Basic?

• If a solution has a pH of 7, then it is neither acidic or basic. pH of 7 is neutral.

• Acids have a pH less than 7.

• Bases have a pH more than 7.

pH in Everyday Life

• Your health depends on controlling your body’s pH.

• It is perfectly normal to find bacteria and fungi growing on human skin. Some of these have been linked to acne.

• Health skin has a natural defense against these micro-organisms.

• Sweat and oil make skin mildly acidic (5.5). This is enough to prevent the organisms from growing out of control.

• Most creams and shampoos are slightly acidic so they maintain a natural acidity of the skin.

• Soaps, however, can have a pH of higher than 7, up to 8! Washing regularly is important, but washing too often can raise the pH of skin, which encourages the growth of skin bacteria.