Applications of Acids, Bases, and Neutralization Reactions

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1 Applications of Acids, Bases, and Neutralization Reactions

2 Agricultural Impacts and Uses The successful growth of plants in agriculture depends on many conditions that must be met for optimal plant growth. Soil ph is one of these conditions. Different plants grow best in different conditions of soil acidity.

3 Changes in soil ph can affect the following aspects of plants growth: Plants can only use dissolved nutrients in the soil. The ph of the soil can affect the composition of dissolved nutrients in the soil

4 Microorganisms usually require environments with a certain ph to thrive. Some microorganisms in the soil can be advantageous to plant growth and soil ph could affect the composition of soil microflora

5 The ph of the soil can affect the colour of flowers and therefore can be useful for producing a desired product

6 Commercial Impacts and Uses Pharmaceutical production changing ph of solutions can cause products to precipitate out of solution. If the precipitate is a desired product, ph can be changed to encourage precipitation. Household pharmaceuticals bases such as antacids can be used to treat heart burn by helping to neutralize stomach acids

7 Commercial Impacts and Uses Household cleaning bases are often found in cleaning products and feel slipper to the touch Pool maintenance pools must be maintained at a near neutral ph to be safe for use and to maintain the effectiveness of the chlorine.

8 Environmental Impacts and Uses Acid precipitation Rain usually has a ph of 5.6. A ph of lower than that is considered acid rain. Acid rain is caused by reactions in the atmosphere involving water and various non-metal oxides. These gases are released into the atmosphere by transportation, various industries, and natural sources. The formation of acid rain is a chain of reactions involving gases released from industry. The two main processes are shown below, involving sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ).

9 Reactions with sulfur dioxide: 1. The combustion of fossil fuels containing sulfur results in the production of sulfur dioxide from sulfur and oxygen S (s) + O 2(g) SO 2(g) 2. The sulfur dioxide gas then further reacts with oxygen to produce sulfur trioxide. 2 SO 2(g) + O 2(g) 2 SO 3(g) 3. This sulfur trioxide gas then reacts with water in the atmosphere to form sulfuric acid. SO 3(g) + H 2 O (l) H 2 SO 4(aq)

10 Reactions with nitrogen oxides: 1. Combustion in engines cause nitrogen gas and oxygen gas to react and form nitrogen monoxide gas. N 2(g) + O 2(g) 2 NO (g) 2. The nitrogen monoxide gas then further reacts with oxygen gas to produce nitrogen dioxide gas. 2 NO (g) + O 2(g) 2 NO 2(g) 3. This nitrogen dioxide gas then reacts with water in the atmosphere to form nitric acid. 3 NO 2(g) + H 2 O (l) 2 HNO 3(aq) + NO (g)

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12 Effects of Acid Rain The effects of acid rain include the following: impacts on aquatic ecosystems as most organisms have a narrow range of ph that is considered optimal changes to soil ph and soil composition economic impacts resulting from loss of product in industry (fishing, agriculture, etc.) or city maintenance and repair of structures

13 Prevention of Acid Rain and Remediation Reduction of NO x and SO 2 emissions Use of catalytic converters in vehicles to reduce NO x emission metal catalysts such as platinum help to reduce the emission of harmful gases

14 Prevention of Acid Rain and Remediation Use of scrubbers in smokestacks to reduce SO 3 the decomposition products of calcium carbonate are used to decrease harmful emissions

15 Prevention of Acid Rain and Remediation Decrease acidity of lakes calcium hydroxide (limewater) is a compound that can be used to neutralize the acidity of lakes. However, liming can have negative impacts such as increasing the calcium content of the lake.

16 Acid Leaching Heavy metals can be released into the environment through many pathways. Acids can react with metals in soil to produce soluble compounds. This process is known as acid leaching. In uncontrolled environments, this can be very damaging as it releases metals and other substances into the surrounding environment. However, acid leaching can also be used to clean up soils in a controlled manner where the soluble compounds (including the unwanted metals) can be removed from the soil.

17 Chemical Spills Large amounts of industrial chemicals are often transported over long distances. If an accident occurs, knowledge of neutralization reactions can be used to clean up spills of large amounts of acid or base. For example, after the derailing of a train in northern Ontario, a large amount of sulfuric acid was spilled and released into the nearby river.

18 Chemical Spills To neutralize the acid, they added calcium oxide (lime) to the river to cause the following chain of reactions which neutralizes the acid: 1. The added calcium oxide reacts with the water in the river to form the base calcium hydroxide. CaO (s) + H 2 O (l) Ca(OH) 2(aq) 2. This calcium hydroxide then reacts with the sulfuric acid in the river in a neutralization reaction. Ca(OH) 2(aq) + H 2 SO 4(aq) 2 H 2 O (l) + CaSO 4(aq)