Chapter 10 - Chemistry of the environment Flashcards
How can water be chemically tested?
Water can be chemically tested using anhydrous cobalt(II) chloride or anhydrous copper(II) sulfate.
What colour is anhydorus and hydrated cobalt(II) chloride?
Anhydrous cobalt(II) chloride, CoCl2, is blue whereas hydrated cobalt(II) chloride, CoCl26H2O, is pink. This test is usually done with cobalt chloride paper.
Anhydrous cobalt(II) chloride + water ⇌ hydrated cobalt(II) chloride
CoCl2 (s) + 6H2O (l) ⇌ CoCl26H2O (s)
What colour is anhydrous and hydrated copper(II) sulfate?
Anhydrous copper(II) sulfate, CuSO4, is white whereas hydrated copper(II) sulfate, CuSO45H2O, is blue.
Anhydrous copper(II) sulfate + water ⇌ hydrated copper(II) sulfate
CuSO4 (s) + 5H2O (l) ⇌ CuSO45H2O (s)
How can you test the purity of water?
The purity of water can be testing using the melting and boiling points. Pure substances melt and boil at specific and sharp temperatures. Water has a melting points of 0°C and a boiling point of 100°C. Impurities tend to increase the boiling point of water and decrease the melting point.
What is distilled water?
Distilled water is water that has been heated to form a vapour and then condensed back to a liquid. This means that it contains very few impurities. Distilled water is used in practical chemistry because of its high purity levels. Tap water is not typically used because it contains more impurities which could interfere with chemical reactions.
What substances may water from natural sources contain?
Water from natural sources may contain substances including dissolved oxygen, metal compounds, plastics, sewage, harmful microbes, nitrate from fertilizers and phosphates from fertilisers and detergents.
What substances found in water from natural sources are beneficial?
Some of these substances are beneficial including dissolved oxygen which is essential for aquatic life and metal compounds as some provide essential minerals which are necessary for life, such as calcium and magnesium.
What substances found in water from natural sources are harmful?
However, some of these substances are harmful including metal compounds that are toxic like aluminium and lead, plastics that may be harmful to aquatic life in many ways, sewage that contains harmful microbes which can cause disease and nitrates and phosphates from fertilisers which can promotes the growth of aquatic plant life which leads to the deoxygenation of water also known as eutrophication.
What are insoluble and soluble impurities?
Untreated wate contains soluble and insoluble impurities. Insoluble impurities include soil and other organic matter. Soluble impurities include dissolved calcium, metallic compounds and other inorganic pollutants.
What is the process of water treatment?
The first step in water treatment is sedimentation and filtration. Water is pumped into sedimentation tanks and allowed to stand for a few hours. Larger particles fall to the bottom of the tank due to gravity and form a layer of sediment. The water is then filtered through sand and gravel to remove smaller particles.
The second step is filtration and treatment with carbon. This removes unpleasant tastes and odours.
The final step is chlorination. Bacteria and other microorganisms are too small to be trapper by the filters, so chlorine is carefully added to the water supply to kill bacteria and other microorganisms.
What are NPK fertilisers?
NPK fertilisers contain nitrogen, potassium and phosphorus for improved plant growth. Nitrogen makes chlorophyll, protein and promotes healthy leaves. Potassium promotes growth and health fruits and flowers. Phosphorus promotes healthy roots. Different fertilisers contain different amounts of fertiliser compounds, so each fertiliser contains different proportions of nitrogen, potassium and phosphorus.
What water soluble ions do fertilisers contain?
Fertiliser compounds contains the following water-soluble ions: ammonium ions, NH4+ , nitrate ions, NO3-, phosphate ions, PO43- and potassium ions, K+.
How are ammonium salts and nitrate salts used in fertilisers?
Ammonium salts and nitrate salts are commonly used as fertilisers including: ammonium nitrate, NH4NO3, ammonium phosphate, (NH4)3PO4 and potassium nitrate, KNO3.
What is the percentage composition of gases in clean, dry air?
The composition of clean, dry air include 78% nitrogen N2, 21% oxygen O2 and the remainder is a mixture of noble gases and carbon dioxide CO2.
Where does carbon dioxide come from and what are the risks of it?
Carbon dioxide comes from the complete combustion of carbon-containing fuels. The adverse effect of carbon dioxide is that higher levels of carbon dioxide leads to increase global warming, which leads to climate change.
Where does carbon monoxide and particulates come from and what are the risks of them?
Carbon monoxide and particulates from the incomplete combustion of carbon-containing fuels. The adverse effect of carbon monoxide is that it’s a toxic gas. The adverse effect of particulars is that there is an increased risk of respiratory problems and cancer.
Where does methane come from and what are the risks of it?
Methane from the decomposition of vegetation and waste gases from digestion in animals. The adverse effect of methane is that higher levels of methane leads to increase global warming, which leads to climate change.
Where do oxides of nitrogen come from and what are the risks of them?
Oxides of nitrogen from car engines. The adverse effect of nitrogen oxides are acid rain, photochemical smog and respiratory problems.
Where does sulphur dioxide come from and what are the risks of it?
Sulphur dioxide from the combustion of fossil fuels which contain sulphur compounds. The adverse effect of sulphur dioxide is acid rain.
What is the enhanced greenhouse effect?
Carbon dioxide and methane can absorb the thermal energy from radiation and re-emit it in all directions. This reduces the thermal energy lost to space and traps it within earths atmosphere, keeping the earth warm and causing the greenhouse effect. As the concentration of greenhouse gases increases due to human activity, more thermal energy is trapped within the earths atmosphere and causing the earths average temperature to rise also known as global warming. This process is called the enhanced greenhouse effect.
How can carbon dioxide emissions be reduced?
Carbon dioxide emissions can be reduced by using hydrogen and renewable energy supplies such as solar or wind energy instead of burning fossil fuels, using more fuel-efficient vehicles, reducing the number of vehicles on the road by using public transport or carpooling, recycling or reusing products made from crude oil, reducing household energy consumption or planting more trees.
How can methane emissions be reduced?
Methane emissions can be reduced by reducing the amount of livestock farming.
How can sulphur dioxide emissions be reduced?
Sulphur dioxide emissions can be reduced by using catalytic converters in vehicles, using fuels which contain low levels of sulphur or using flue gas desulphurisation with calcium oxide. Flue gas desulphurisation brings waste gases from coal fired power stations and passing them through a scrubbing chamber, they are sprayed with a wet slurry of calcium oxide and calcium carbonate and the calcium compounds react with the sulphur dioxide to produce calcium sulphate.
How can emissions of nitrogen oxides be reduced?
Oxide of nitrogen are formed when the nitrogen and oxygen react in high pressure and temperature conditions of internal combustion engines or blast furnaces. Exhaust gases also contain unburned hydrocarbons and carbon monoxide. Cars are fitted with catalytic converters which form a part of their exhaust systems.
What are catalytic converters?
Catalytic converters contain a series of transition metal catalysts like platinum and rhodium. These metal catalysts are in a honeycomb within the converted to increase the surface area available for reaction. A series of redox reactions occurs which neutralises the pollutant gases.
Carbon monoxide is oxidised to carbon dioxide 2CO + O2 → 2CO2
Oxides of nitrogen are reduced to N2 gas 2NO → N2 + O2 and 2NO2 → N2 + 2O2
A single reaction can summarise the reaction of nitrogen monoxide and carbon monoxide within a catalytic converter. 2NO + 2CO → N2 + 2CO2
What is photosynthesis?
Photosynthesis is the reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light. The word equation is carbon dioxide + water → glucose + oxygen. The balances symbol equation is 6CO2 + 6H2O → C6H12O6 + 6O2.
