Chemistry and the environment · Química e meio ambiente
| English | Português |
|---|---|
| combustion/kəmˈbʌstʃn/ | combustão |
| greenhouse effect/ˈɡriːnhaʊs ɪˈfekt/ | efeito estufa |
| acid rain/ˈæsɪd reɪn/ | chuva ácida |
| pollution/pəˈluːʃn/ | poluição |
A lower concentration leaves two outputs
- In an invented treatment, 10.0 L of liquid falls from 12.0 to 3.0 mg/L of one substance. Assume liquid volume stays unchanged and all substance removed from the liquid is retained on the filter.
- The initial mass is 120 mg; 30 mg remains in liquid and 90 mg is on the filter. This is redistribution under the assumptions, not destruction of the substance.
Which interpretation fits the fictional filter treatment?
The record accounts for substance in two outputs. Ninety milligrams remain on the filter, while thirty remain in liquid; removal from one output is not destruction.
Calculate mass and percentage reduction
- Mass follows $m=cV$: $m_{\text{initial}}=12.0\times10.0=120\ \text{mg}$ and · e $m_{\text{liquid}}=3.0\times10.0=30\ \text{mg}$. The filter retains $m_{\text{filter}}=120-30=90\ \text{mg}$.
- Concentration reduction is $R=((c_{\text{initial}}-c_{\text{final}})/c_{\text{initial}})\times100\%=((12.0-3.0)/12.0)\times100\%=75\%$. Final concentration 3.0 mg/L still exceeds the fictional task target 2.0 mg/L.
At unchanged 10.0 L volume, concentration falls from 12.0 to 3.0 mg/L. Assuming all removed substance remains on the filter, what filter mass is retained in mg?
m = cV gives 120 and 30 mg; the difference is 90 mg.
What percentage reduction follows when concentration falls from 12.0 to 3.0 mg/L? Give the percentage number.
R = (12.0 - 3.0)/12.0 × 100 = 75%.
Explain greenhouse gases by radiation
- Combustion · Combustão 燃烧 of carbon-containing fuels can release carbon dioxide. In the greenhouse effect 温室效应, gases such as carbon dioxide absorb and emit thermal infrared radiation.
- The natural mechanism and changes in its effects are distinct questions. It is not the same process as depletion of stratospheric ozone. Source checked 2 October 2026: NASA radiation budget.
Which account distinguishes the natural greenhouse mechanism from a question about its change?
Greenhouse gases absorb and emit thermal infrared. The existence of the mechanism and changes in its effects are distinct questions; it is not the same as ozone depletion.
The greenhouse effect and the hole in the ozone layer are the same phenomenon.
Greenhouse radiation effects and ozone depletion involve different processes. Do not substitute one mechanism for the other.
Explain acid deposition by chemistry
- Acid rain 酸雨 involves sulfur dioxide and nitrogen oxides reacting in the atmosphere with water, oxygen and other chemicals to form acidic compounds. The chemistry is more than simply dissolving any gas in water vapour.
- Name the substance, source, mechanism, effect and relevant mitigation. Do not substitute a greenhouse-radiation explanation for acid-deposition chemistry. Source checked 2 October 2026: EPA explanation.
Order these parts of a structured environmental explanation.
This is a useful explanation sequence, not a promise of five marks or proof that every pollutant has the same effects.
Write the mechanism step for nitrogen oxides forming acid rain.
Example: “Nitrogen oxides react in the atmosphere to form acidic compounds that contribute to acid deposition.”
Follow the pathway when assessing mitigation
- Pollution · Poluição 污染 depends on substance, amount, pathway and effects. A filter may reduce one output while creating a concentrated waste that still needs appropriate handling.
- A mitigation should be evaluated against its stated criterion and other impacts. Reducing one substance does not automatically solve every environmental mechanism or establish drinking-water safety.
The fictional concentration target is missed because 3.0 mg/L is greater than 2.0 mg/L. A 75% reduction is a useful result, but “passed the target” and “safe to discharge” do not follow from it.
The final 3.0 mg/L meets the fictional maximum task target 2.0 mg/L because reduction was 75%.
False: compare final concentration with target; 3.0 is greater than 2.0.
Keep results, standards and actions separate
- State which quantities were supplied, which were calculated, and where the substance went. The task target is an invented teaching condition, not a real regulatory standard.
- Other substances, energy use and waste handling remain unassessed. Students analyse the supplied record; real treatment or discharge requires authorised procedures and assessment.
Check $m=cV$, account for both outputs, and compare the actual final concentration with the stated target. A percentage reduction alone is not a complete safety conclusion.