Topic 3: How do you spell relief? Unit 3 – Environmental Chemistry

Sec. 6.1 Properties of Acids and Bases

• Acids• Blue litmus to red• pH < 7• High conductivity• Taste sour• Neutralize bases• Reactive with active

metalseg. Zn or Mg to form H2 (g)

• Bases• Red litmus to blue• pH > 7• High conductivity• Taste bitter• Neutralize acids• Feels slippery• Ionic compounds

• Acids and Bases can be defined by their properties (operational definition)

The pH scale

Acid – Base Indicators • Indicators

• Substances that change color when the acidity changes

• Synthetic dyes, plant compounds

• When changing from its acid form to its basic form it will be a blend of its 2 colors.

• Eg. Litmus at pH < 6 is red pH > 8 is blue

pH 6-8 is purple

Using Indicators

• pH test strips• These are papers with a combo of indicators to give a color

range that matches a pH range.

pH meters• Digital pH

meters can give an accurate pH.

Neutralization Reaction

• The reaction between an acid and a base• Acid + Base Salt + Water

• We often want to control acid effects:• Acid precipitation causes buildings/statues to corrode• It is caused by pollution reacting with water in the air.• Soil conditions change and plants can’t grow properly• Fish die in polluted waters

Liming

• A neutralization reaction that uses lime (calcium carbonate – CaCO3)

• It’s released by aircraft into a lake where it reacts with acid and the acid gets neutralized.

Controlling Emissions

• Emissions are the pollutants from smokestacks and vehicle exhaust.

• For vehicle exhaust cars are equipped with Catalytic Converters.• They help hydrocarbons combust

better and release less pollution.

Catalytic Converter

Scrubber