Somewhere within a few hours of here, a reaction you can now write down is running at a scale of tonnes per hour. It is making something people need. It is also producing something nobody asked for, and somebody whose house is nearby has an opinion about that.
Your job is to take one such process apart into equations, work out what the chemistry actually predicts, and then say — with the equations in front of you — how well the industry’s answer to the unwanted product works.
The situation
Industrial chemistry is not school chemistry made bigger. The reactions are the same and the constraints are completely different: cost, continuous operation, what to do with a by-product you produce a thousand tonnes of, and a community that lives with the result.
You are writing for people who are not chemists but are affected. A community newsletter, a public meeting, a briefing for a municipal council considering a permit, a submission from a student group. Name your audience on the first line, because who is reading changes what belongs in the piece.
Processes that work well for this task, all of them real and all of them documented by the companies and the agencies that regulate them:
- Pulp and paper. The chemical recovery cycle, and what leaves in the effluent and the stack.
- Smelting and roasting sulfide ores. Sulfur dioxide, what it does when it meets water, and what a smelter does with it.
- Drinking water treatment. Coagulation, disinfection, and the trade-off between killing pathogens and forming by-products.
- Lime and cement production. A decomposition reaction that releases carbon dioxide from the rock itself, before any fuel is burned.
- Fertiliser manufacture, and what happens to nitrogen compounds that leave a field.
- Mine drainage neutralisation, where an acid is treated with a base at enormous scale.
- Flue gas treatment, where a gas is removed from a stack by reacting it with something cheap.
- Metal recycling or electroplating, and the solutions left over.
You may propose a different process. Bring it early — some come back for a redesign, because a process with no accessible documentation makes for a task you cannot complete honestly.
What you have to work out
The chemistry, written properly. At least four balanced equations covering the main reaction and the treatment of a by-product. States included. Every formula correct — a briefing note with a wrong formula in it loses the reader who knows and misleads the one who does not.
A prediction section, which is the assessed thinking. I will give each of you two reactions related to your process, with the reactants and no products. You predict the products, justify the prediction from the type of reaction, and say what test would confirm it. This is the part that cannot be researched, and it is worth the most.
The prediction patterns you should be able to apply
These are the ones that come up constantly in industrial contexts, and each is a synthesis or a decomposition whose products follow from the pattern rather than from memory.
A metal oxide plus water gives a base. — the solution turns an indicator toward the basic end, which is the result you got from magnesium oxide in Oxides and Neutralisation.
A non-metal oxide plus water gives an acid. , and with further oxidation followed by . This chain is why a sulfur-bearing stack gas is an acidification problem downwind and not merely a smell.
A metal carbonate decomposes on strong heating to the oxide and carbon dioxide. — worth noticing that this carbon dioxide comes out of the rock, so it is emitted even if the kiln is heated by something carbon-free.
Acid plus base gives a salt and water. — this is how acidic drainage is treated at scale, and the reason the base chosen is usually a cheap calcium compound.
A gas can be removed by reacting it with a cheap solid. , and then . One unwanted gas has been turned into a solid — and into a different gas. Whether that is a good trade is exactly the kind of judgement this task is asking for.
Apply the pattern, then check the formula you have written is a real compound with sensible charges. A prediction that produces has gone wrong at the charge-balance step, not at the pattern step.
An assessment of how well the solution works. Not whether the process is good or bad. Whether the chemical answer to the by-product problem actually addresses it, and what it costs:
- What does the treatment remove, and how completely?
- What does it produce instead, and where does that go?
- What does it cost — in energy, in reagent, in a solid that now has to be stored somewhere?
- What would happen if it were not done at all?
A treatment that converts a gas into a solid has not made the material disappear. It has moved the problem into a different form, and often a much better one. Say which, and say why you think so.
What to hand in
A briefing note of two to three pages, addressed to your named audience, containing:
- What the process makes and why anybody wants it. Start here. Writing about an industry as though its product were unnecessary is the fastest way to lose a reader who works there.
- The chemistry, in plain language, with the equations in an appendix rather than in the middle of a sentence.
- The by-product problem, quantified where you can find a traceable figure and described qualitatively where you cannot.
- The treatment, and your assessment of how effective it is.
- What you would want to know that you could not find out. This section is short and it is marked.
An equations appendix, one page: every equation balanced, with states, and one line each on what it is doing in the process.
Your prediction section, one page: the two reactions I gave you, your predicted products, the reaction type that justifies each prediction, and the test that would confirm it.
Sources, cited in the format in Writing About Chemistry. Three at minimum, of the right kinds: a government or regulatory agency, a company’s own published environmental or technical documentation, a professional or standards body, a peer-reviewed article. Every figure traceable to something a reader can open.
On numbers you cannot verify
Industrial emission and production figures are published, and they are also widely repeated at second hand with the units mangled. If you cannot find the figure at its source, write that you could not. That sentence is worth more than a number you cannot defend, and it is the only version of this task that is honest. Never invent a figure, a study, or an organisation to fill a gap in a paragraph. See What Counts as Evidence.
How it will be judged
| What I am looking for | Level 3 sounds like | Level 4 sounds like |
|---|---|---|
| The equations | Balanced, correct formulas, states included | Balanced, and each one is placed where it explains something the reader needed |
| Predicting products | Correct products for the given reactions | Correct, justified by reaction type, and a specific confirming test named |
| Understanding the process | Describes what happens accurately | Explains why the process is arranged that way, including the constraints |
| The by-product problem | Identified, with a source | Quantified where possible, and the limits of the figure stated |
| Assessing the treatment | Says whether it works | Says how completely, what it produces instead, and what it costs |
| Audience | Written clearly | Written so that the named audience could act on it, without talking down |
| Sources | Three appropriate sources | Sources matched to the claims they support, with their limits noted |
| Honesty | Notes an uncertainty | Names what could not be found out and how that weakens the conclusion |
What sinks an otherwise good briefing
- An unbalanced equation. It undermines everything else on the page, because a reader who spots it has no way to know what else is wrong.
- Treating the industry as the villain or the hero. Both are positions taken before the evidence, and both read as such.
- A by-product figure with no unit or no time base. “Emits 4000” is not a quantity. Tonnes per year? Kilograms per tonne of product?
- Confusing removal with elimination. Scrubbing a gas produces a solid that has to go somewhere, and a briefing that stops at “the gas is removed” has told half the story.
- A prediction copied from the research rather than derived. The prediction section exists precisely because it cannot be looked up. Show the reaction type and let the products follow.
- A recommendation with no cost in it. Everything costs somebody something, and naming it is what separates advice from opinion.
Wider context and the discussion this connects to: Chemistry at Industrial Scale.
Curriculum connection
C1.1
analyse, on the basis of research, chemical reactions used in various industrial processes (e.g., pulp and paper production, mining, chemical manufacturing) that can have an impact on the health and safety of local populations [IP, PR, AI, C]
Link to original
C1.2
assess the effectiveness of some applications of chemical reactions that are used to address social and environmental needs and problems [AI, C]
Link to original
C2.4
predict the products of different types of synthesis and decomposition reactions (e.g., synthesis reactions in which simple compounds are formed; synthesis reactions of metallic or non-metallic oxides with water; decomposition reactions, in which a chemical compound is separated into several compounds) [AI]
Link to original