7.1.1Additional lessons
Safety, Ethical and Environmental Issues in Chemistry — IB Chemistry HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 158 of 172
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Section 1 of 5Safety and Risk Assessment
A risk assessment should be completed before any practical work starts.
Hazard and risk
- Hazard and risk A hazard is something that can cause harm, while the risk is the chance that harm will occur.
Hazard labels
- Hazard labels Pictograms indicate whether a substance is corrosive, flammable, toxic, an irritant, oxidising or harmful to the environment.
Control measures
- Control measures Safety goggles, gloves, a fume cupboard and keeping flammable liquids away from flames reduce the risk.
Safety data
- Safety data Safety data sheets give the properties, hazards, first-aid actions and disposal advice for each chemical.
Section 2 of 5Ethical Issues
1
Record and report data honestly, without changing results to fit what you expected to find.
2
Acknowledge the work of others and cite sources, avoiding any form of plagiarism.
3
Where animals or human participants are involved, follow the school and IB rules on consent, welfare and minimal harm.
4
Share responsibility fairly in group work and make sure that all contributions are recognised.
5
Consider the wider effects of chemistry, such as who benefits from a new product and who may be harmed.
Section 3 of 5Environmental Responsibility
Environmental Responsibility
Waste disposal
- Waste disposal Heavy metal solutions, organic solvents and halogenated waste are collected separately and never poured down the sink.
Scale
- Scale Using small quantities, such as microscale methods, reduces waste, cost and exposure to hazards.
Green chemistry
- Green chemistry Choose reactions with high atom economy, less hazardous reagents, and fewer steps where possible.
Atom economy
- Atom economy Atom economy = (molar mass of desired product ÷ total molar mass of reactants) × 100%.
| Hazard | Typical example | Precaution |
|---|---|---|
| Corrosive | Concentrated acids | Goggles, gloves, dilute where possible |
| Flammable | Ethanol, propanone | No naked flames, use a water bath |
| Toxic | Bromine, cyanide | Fume cupboard |
Section 4 of 5Worked Example
Question
- Calculate the atom economy of making ethanol from bromoethane: C₂H₅Br + NaOH → C₂H₅OH + NaBr.
- (Mr: C₂H₅Br = 108.97, NaOH = 40.00, C₂H₅OH = 46.07)
- Total mass of reactants = 108.97 + 40.00 = 148.97.
- Mass of desired product = 46.07.
- Atom economy = 46.07 ÷ 148.97 × 100 = 30.9%.
Answer
- Atom economy = 30.9%, which is low because sodium bromide is a waste product;
- hydration of ethene to make ethanol has an atom economy of 100%.
Section 5 of 5Exam Checklist & Tips
7.1.1 – Key Points for the Exam
- Hazard A property of a substance or process that can cause harm.
- Risk The likelihood that a hazard will cause harm.
- Atom economy The percentage of the mass of reactants that ends up in the desired product.
- Green chemistry Designing processes to reduce waste and the use of hazardous substances.
Common Mistakes
- Mixing up hazard and risk, treating them as the same idea.
- Pouring organic or heavy metal waste down the drain.
- Omitting control measures from a risk assessment.
- Presenting only the best results and hiding the outliers.
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