ACIDS & BASES

FIRST A REVIEW: FUEL COMBUSTION

Coal, oil, and natural gas are called fossil fuels because they are formed from dead plants and animals.

THEY ARE CALLED HYDROCARBONS

Because they are mainly made up of the elements hydrogen and carbon.

Also may contain: oxygen, nitrogen, sulfur, mercury, lead.

When burned in homes, vehicles, and industrial plants, they produce large amounts of carbon dioxide and water vapour.

GENERAL REACTION EQUATION FOR THIS COMBUSTION REACTION.

hydrocarbon + oxygen

carbon dioxide + water + energy

INDUSTRIAL PROCESSES

Electric power generation, mineral processing, and fertilizer production may release chemicals into the air.

Natural gas processing is a common industrial process in Alberta; processed into its components for different uses.

Methane, propane, butane- all derived from natural gas, mainly used for heating.

Ethane- used in plastics such as polyethylene.

NATURAL GAS IS PROCESSED TO REMOVE UNWANTED SUBSTANCES:

Hydrogen sulfide- poisonous chemical.

Natural gas that contains it is called “sour” gas.

If not hydrogen sulfide is present, the gas is considered “sweet”

The process for removing hydrogen sulfide produces sulfur dioxide. It is the law in Alberta that companies have to restrict their sulfur dioxide emissions.

WHY CARE?

Video

ACIDS AND BASES

Acid: is a compound that dissolves in water to for a solution with a pH lower than 7.

pH number of a solution indicates (is a measure) of its acidity.

INDUSTRIAL PROCESSES & FUEL COMBUSTION:

Produce large quantities of chemicals, which in the air, dissolve in water droplets to form acids.

Sulfur dioxide combines with water to form sulfuric acid.

Nitrogen oxide combines with water to form nitric acid.

Carbon dioxide combines with water to form carbonic acid.

ALL OF THESE DROPLETS THEN FALL AS ACID RAIN.

ACIDS CAN BE BENEFICIAL

Vinegar, lemon juice… some types of plants, such as blueberries, grow better in acid soils.

BASE

Is a compound that dissolves in water to from a solution with a pH higher than 7.

PH SCALE

Is a measure of a range… pH of 0 is very acidic, pH of 14 is very basic or alkaline.

A pH of 7 means that a solution is neutral- it’s neither an acid or a base.

MEASURING PH

(1) pH meter or (2) acid-base indicators

1. Probe is attached to a meter, submerge the tip into a fluid, meter indicates the fluid’s pH

2. INDICATOR STRIPS CHANGE COLOUR WHEN THEY ARE PLACED IN SOLUTIONS.

Blue litmus paper turns red in an acid, red litmus paper turns blue in a base.

Universal indicator: mixture of colours that change colour over a wide pH range.

NEUTRALIZATION

Antacid- you might have taken one of these if you have an upset stomach.

Antacids are mild bases that react to the acid in your stomach to neutralize it.

THIS ACID-BASE COMBINATION IS CALLED NEUTRALIZATION.

The neutralization reaction produces water and a compound called a salt.

NEUTRALIZING THE EFFECTS OF ACID RAIN

pH of around 5.6 to 3 (central Canada)

Many lakes in Ontario and Quebec became so acidic that organisms could no longer survive in them.

Acid lakes are sometimes treated with lime (calcium hydroxide)-a base- to neutralize them.

Reaction produces calcium sulfide (a salt) and water. If all the acid and all the base are used up, the solution becomes neutral.

REACTION EQUATION

HOMEWORK

Hand in: Check & Reflect, page 195, 1-5 for Monday.

Read Text: Section 1.3 Common Substances essential to living things, pages 196-204