Industrial Reactions, Health and Safety

Chemistry at the scale of a city

The reactions in this unit are not only test-tube chemistry. Some of them run day and night in huge plants: blast furnaces in Hamilton, nickel and copper smelters in Sudbury, fertilizer plants, cement kilns and the petrochemical plants near Sarnia. These industries provide jobs and materials Canadians use every day (steel for cars and bridges, fertilizer for food, cement for buildings). They can also release substances that affect the health and safety of workers and of the people who live nearby.

In this lesson you will write the main reactions, classify them, and look at their effects. Your curriculum asks you to analyse these impacts using research, so you will also practise finding and judging good sources.

Steelmaking: the blast furnace

Iron ore contains iron oxides such as Fe₂O₃. A blast furnace turns it into iron using coke (carbon) and limestone. Hot air is blown in near the bottom.

1. Coke burns (combustion/synthesis): C(s) + O₂(g) → CO₂(g)
2. Carbon dioxide meets more hot coke and forms carbon monoxide (synthesis): CO₂(g) + C(s) → 2CO(g)
3. Carbon monoxide removes oxygen from the iron ore: Fe₂O₃(s) + 3CO(g) → 2Fe(l) + 3CO₂(g)
4. Limestone decomposes: CaCO₃(s) → CaO(s) + CO₂(g), and the lime combines with sandy impurities (silica) to form slag (synthesis): CaO(s) + SiO₂(s) → CaSiO₃(l)

Reaction 3 is not one of our five simple types. It is an oxidation-reduction reaction, which you will study in Grade 12 Chemistry (SCH4U).

Health and environment: blast furnaces and the coke ovens that make coke release carbon dioxide, carbon monoxide, sulfur dioxide, dust and other pollutants. Carbon monoxide inside the plant is a serious workplace hazard. Air quality near heavy industry has long been a concern for residents of neighbourhoods near Hamilton's steel mills and other heavy industry. Ontario steelmakers are moving to electric arc furnaces, which melt scrap steel (or iron made with natural gas) using electricity and release much less carbon dioxide: Algoma Steel in Sault Ste. Marie shut down its blast furnace and switched to electric arc steelmaking at the start of 2026, and ArcelorMittal Dofasco in Hamilton has announced plans to make a similar change.

Smelting sulfide ores: Sudbury and acid rain

Nickel and copper in the Sudbury area are found as sulfide ores. Smelting begins by roasting them in air, which releases sulfur dioxide:

• 2NiS(s) + 3O₂(g) → 2NiO(s) + 2SO₂(g)
• Cu₂S(s) + O₂(g) → 2Cu(l) + SO₂(g)

In the air, sulfur dioxide forms sulfur trioxide and then sulfuric acid (two synthesis reactions you met earlier), which falls as acid precipitation. For decades, Sudbury's smelters released huge amounts of sulfur dioxide. Together with logging and wood fires used in early roasting, it left large areas of bare, blackened rock, and many nearby lakes became too acidic for fish. In 1972 a 381-metre "Superstack" went into full operation. It improved air quality nearby by spreading the gas higher and farther, but it did not reduce the total amount released. (After further emission cuts, it was taken out of service in 2020 and is being dismantled.)

Since then, the companies have captured most of the sulfur dioxide and turned it into sulfuric acid to sell, cutting emissions dramatically. A long-running community regreening program has spread crushed limestone on acidic soils and planted millions of trees, and many lakes have recovered. Sudbury is now studied around the world as an example of environmental recovery.

Other industrial reactions with health and safety risks

• Ammonia (Haber process): N₂(g) + 3H₂(g) → 2NH₃(g), at high pressure and temperature with an iron catalyst. Ammonia makes fertilizers that feed billions of people. But ammonia gas is toxic and corrosive, and leaks from refrigeration systems (such as those in some arenas) and plants are dangerous to workers and neighbours. The fertilizer ammonium nitrate can explode if stored improperly or exposed to fire, so its storage is strictly regulated.
• Chlorine and sodium hydroxide (chlor-alkali process): electrolysis of salt water, 2NaCl(aq) + 2H₂O(l) → 2NaOH(aq) + H₂(g) + Cl₂(g). Chlorine disinfects drinking water and is used to make plastics such as PVC, but chlorine gas is very toxic, so it is transported and stored under strict rules.
• Cement: heating limestone, CaCO₃(s) → CaO(s) + CO₂(g), releases carbon dioxide from the reaction itself as well as from the fuel burned to heat the kiln. Cement making is one of the largest industrial sources of carbon dioxide in the world.
• Petrochemical plants near Sarnia process oil and gas into fuels and plastics. Aamjiwnaang First Nation, a community located beside many of these plants, has raised concerns for years about air pollution, chemical releases and the health of its members, and has pushed governments and companies for better monitoring and stronger protections. Their experience is part of a wider discussion about who lives closest to industrial pollution and who has a say in decisions about it.

Researching an industrial issue: finding good sources

To analyse an issue, you need reliable information. Good places to start:

• Government data: the federal National Pollutant Release Inventory (NPRI) lets anyone look up the pollutants that large facilities across Canada report releasing. Ontario's Air Quality Health Index reports daily air quality.
• Peer-reviewed research, university and public-health reports.
• Reports from companies, community groups and advocacy groups, which can be valuable but may have a point of view.

Evaluate each source: Who wrote it, and what are their qualifications? When was it published or updated? What is its purpose (to inform, to sell, to persuade)? Is the data supported by evidence and consistent with other sources? Then cite each source you use, in the format your teacher asks for (for example APA: author, year, title, publisher or website, URL).