9.4.A - Chemical Monitoring


Chemistry is the science that studies matter - its chemical and physical properties, the chemical and physical changes it undergoes and the energy changes that accompany these processes.

No one can know all there is to know about chemistry, so it is divided up into a number of different study areas where chemists specialise. Chemists with different specialisations can then collaborate more effectively on various projects.

Many chemical occupations will require chemists to monitoring and manage the products of reactions in order to ensure safety, efficiency and even high yeilds in production processes.

In this topic students:

  • Identify and account for reactions that need monitoring
  • Investigate chemical specialties and occupations


Need for Monitoring

In many chemical industries, products are formed that need monitoring for one reason or another. The products may be toxic, carcinogenic or flammable or it may be an equilibrium system where yeild can be increased by monitoring various reaction conditions.

In some reactions, different products are formed when the conditions change. These need to be monitored to maximise one product and reduce other harmful products. An example is the combustion of octane in the internal combustion engine of a car. When an engine is new, it works most efficiently and bums the fuel more completely to produce carbon dioxide and water. Although carbon dioxide is a greenhouse gas, it is harmless to humans and preferable to the alternative products.

C8H18 (l) + 25/2 O2 (g) ⇒ 8CO2 (g) + 9H20 (l)

As the engine ages, it burns octane less efficiently and partial combustion occurs producing carbon monoxide in preference to carbon dioxide. Partial combustion occurs due to the lack of oxygen available. To burn one mole of fuel in the equation below, only 8.5 mol of oxygen is needed compared to 12.5 mol in the equation above.

C8H18 (l) + 17/2 O2 (g) ⇒ 8CO (g) + 9H20 (l)

When oxygen becomes even more limiting (4.5 mol), carbon (soot) is produced in preference to carbon oxldes.

C8H18 (l) + 9/2 O2 (g) ⇒ 8C (S) + 9H20 (l)

Both carbon monoxide and soot are more harmful to humans than carbon dioxide. Carbon monoxide is highly toxic and soot is carcinogenic (cancer causing). For these reasons the gas makeup of exhaust fuel needs monitoring. This would be done when a new car is tested before leaving the factory and again each time the car is serviced to ensure the air-fuel ratio promotes complete combustion.

 

Chemical Occupations

Chemists work in a varlety of occupations, some of which are given below:

  • Analytical chemists determine the quantitative composition of materials. They work in the mining industry where they identify the composition of ores. They work for the government where they determine the composition of pollutant gases in the atmosphere and dissolved substances in waterways.

  • Biochemists study the chemistry of living things. They work in the medical Industry on enzyme structure and function, on hormones, proteins and the various chemical pathvvays operating vwthln humans. They work in the agriculture industry on nutrients required by crops and on the various conditions needed for optimal growth of plants.

  • Polymer chemists research and develop new plastics, synthetic fibres, colloids and biopolymers. They work for chemical engtneering companies that aim to produce a variety of new materials.

  • Industrial chemists research new materials. They may work for a petrochemical company, pharmaceutical company, paint industry, CSIRO or in research and development for any varlety of companies.

Collaboration Between Chemists

Chemists collaborate when they collect and analyse data. For example a team of chemists is involved in the ice core work in Antarctlca. Some devise the technique for obtaining the gas samples from the ice cores. Others analyse radioisotopes to date the sample. Others collect the data and yet others analyse what the data shows.

Chemists need to collaborate because they specialise early in their careers and are not expert in a wide variety of fields.