Term
| Why does oxygen have a low solubility in water? |
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Definition
| Diatomic oxygen is a non-polar molecule |
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Term
| What is oxygen's solubility in water at 20°C |
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Definition
| 9 ppm (parts per million) |
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Term
| What happens to the solubility of gases as the temperature increases? |
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Definition
| It decreases (in contrast to most solids) |
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Term
| What determines the quality of water? |
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Definition
| The amount of oxygen. 8-9 ppm is high quality, below 4.5 ppm is highly polluted. |
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Term
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Definition
| The Biochemical Oxygen Demand - a measure of the amount of oxygen consumed by organic wastes and ammonia in a given amount of water at 20°C over 5 days |
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Term
| How can water quality be defined in terms of BOD? |
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Definition
| < 1 = almost pure water, 5 = doubtful purity, 20 = unacceptable purity |
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Term
| What happens during aerobic decomposition of organic matter in water? |
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Definition
| In the presence of oxygen, bacteria break down organic matter into H2O, CO2, NO3(-), SO4(2-) and PO4(3-). |
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Term
| What happens when there is too much aerobic decomposition? |
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Definition
| Aerobic decomposition uses oxygen, so too much organic wastes will lower the amount of dissolved oxygen and may kill aquatic life. |
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Term
| What happens during anaerobic decomposition of organic matter in water? |
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Definition
| In the absence of oxygen, microorganisms break down organic matter into NH3, amines, CH4, PH3 and H2S |
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Term
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Definition
| Part of the water becomes lifeless (fish die of asphyxiation due to lack of oxygen, anaerobic processes result in toxins) |
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Term
| What leads to eutrophication? |
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Definition
| Nitrate plant nutrients, waste, detergents and fertilisers lead to excessive growth of plant life -> shell fish die -> more toxins -> plants die and are decomposed aerobically -> DO is decreased. |
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Term
| How do power plants and industrial processes pollute water? |
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Definition
| Water is used as a coolant, and hot water in rivers leads to thermal pollution -> high temperature decreases oxygen solubility. |
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