Group 5A(15) Elements Nitrogen is a diatomic gas (N2) with a very low boiling point, due to its very weak intermolecular forces. Phosphorus exists most commonly as tetrahedral P4 molecules. It has stronger dispersion forces than N2. Arsenic exists as extended sheets of As atoms covalently bonded together. The covalent network structure gives it a high melting point. Antimony also has a covalent network structure. Bismuth has metallic bonding. Its melting point is lower than that of As or Sb.

Learning Objectives Nitrogen and Sulfur 12:1B Learners can: - evaluate ways of minimising these environmental impacts - know and understand the environmental impact of oxides of nitrogen in the atmosphere and nitrates in soils and water supplies - be able to evaluate ways of minimising these environmental impacts - know the occurrence of sulphur - understand the structure and allotropy of sulphur - know the sources of sulphur dioxide in the atmosphere and understand its consequences, including the formation and effects of acid rain - understand the need for food preservatives and know the use of sulphur dioxide for this purpose - understand the role of sulphuric acid as an acid and as an oxidising agent - recall at least one process for the manufacture of sulphuric acid in terms of an equilibrium process and know its major uses as an industrial chemical - understand the environmental impact of sulphuric acid manufacture

Nitrogen Nitrogen is required by living things to manufacture various items. Integral component of DNA Amino acids

Nitrogen Although almost 80% of the air is N2 , BUT you can’t get the N2 your body needs by breathing nitrogen gas. - Bacteria in the soil must first change N2 into NO3 (nitrates) that can be absorbed by the plants, then to the animals. It Is called the N2 cycle. Without this process, most plants and animals would not have the nitrogen needed to live.

N,P, and K Phosphorous compounds are essential ingredients for teeth and bones. Plants also need phosphorus, so it is one of the nutrients in most fertilizers.

Haber Process nitrogen + hydrogen  ammonia N2(g) + 3H2(g)  2NH3(g) 450ºC, 200 atm, Fe catalyst

How Acid Deposition Develops

Acid Deposition Natural formation by lightning , volcanoes, and respiration, dissolving make natural acids in rain. But , each of these sources are accentuated by man, mostly in car exhaust

Effects of Acid Deposition Declining Aquatic Populations 1) Thin-shelled eggs prevent bird reproduction (Because Ca is unavailable in acidic soil) 2) Acid rain can cause the oceans acidity to rise, making it more difficult for different coastal species to create their exoskeletons that they need to survive.  Picture: Forest decline Ex: Black forest in Germany (50% is destroyed)

Acid Deposition and Forest Decline

Air Pollution Around the World Air quality is deteriorating rapidly in developing countries Shenyang, China Residents only see sunlight a few weeks each year Developing countries have older cars Still use leaded gasoline 5 worst cities in world Beijing, China; Mexico City, Mexico; Shanghai, China; Tehran, Iran; and Calcutta, India

Location A catalytic converter provides an environment for a chemical reaction wherein toxic combustion by-products are converted to less-toxic substances. The honey-comb surface increases the amount of surface area available to support the catalyst, and therefore is often called . The catalyst is Platinum and Palladium and rhodium are 3 precious metals used.

The catalyst is Platinum is the most active catalyst and is widely used. Palladium and rhodium are two other precious metals used iron, manganese and nickel are also used.

Catalytic Converters. 2NOx → xO2 + N2 2CO + O2 → 2CO2 CxHy + O2 → xCO2 + H2O 2NOx → xO2 + N2

Damage to Catalytic Converters Catalyst poisoning occurs when the catalytic converter is exposed to exhaust containing substances that coat the working surfaces, encapsulating the catalyst so that it cannot contact and treat the exhaust. The most notable contaminant is lead .

The Environmental Impact of Catalytic Converters Reduces fuel economy of cars resulting in a greater use of fossil fuels. Although catalytic converters are effective at removing hydrocarbons and other harmful emissions, most of exhaust gas leaving the engine through a catalytic converter is carbon dioxide (CO2), which is responsible for the green house effect. Catalytic converter production requires palladium and/or platinum; part of the world supply of these precious metals is

Phosphorous The element phosphorus comes in two forms—white and red. White phosphorus is so active it can’t be exposed to oxygen in the air or it will burst into flames. The heads of matches contain the less active red phosphorus, which ignites from the heat produced by friction when the match is struck.

Two allotropes of phosphorous. Figure 14.16 Two allotropes of phosphorous. Strained bonds in P4 White phosphorous (P4) Red phosphorous

Representative Elements N,P, and K Phosphorous compounds are essential ingredients for teeth and bones. Plants also need phosphorus, so it is one of the nutrients in most fertilizers.

Table 14.3 Structures and Properties of the Nitrogen Oxides

Nitrogen Oxoacids and Oxoanions Nitric acid (HNO3) is produced by the Ostwald process: The third step is 3NO2(g) + H2O (l) → 2HNO3 + NO(g) Nitric acid is a strong oxidizing agent as well as a strong acid. The nitrate (NO3-) also acts as an oxidizing agent. All nitrate salts are water soluble. Nitrous acid (HNO2) is a much weaker acid than nitric acid. This follows the general pattern for oxoacids – the more O atoms bonded to the central nonmetal, the stronger the acid.

Figure 14.17 The structures of nitric and nitrous acids and their oxoanions.

Figure 14.18 Important oxides of phosphorous. P4O6 has P in its +3 oxidation state. P4O10 has P in its +5 oxidation state. This compound is a powerful drying agent.

Oxoacids of Phosphorus H3PO3 has only two acidic H atoms; the third is bonded to the central P and does not dissociate. H3PO4 has three acidic H atoms. It is a weak acid, but in strong base all three H+ are lost to give the phosphate anion.