Chemistry C4

What is Ammonia? 

• Alkaline Gas (NH3)
• Made from Hydrogen and Nitrogen
• NITROGEN + HYDROGEN  <--> AMMONIA 
• It is a reversible reaction
• Can be used to make cleaning fluids, nitric acid and fertilisers
• cheap fertilizer made from ammonia to grow food for the large population 

The Haber Process: 

N2 + 3H2 <--> 2NH3

1 PART NITROGEN, 3 PARTS HYDROGEN COMRESSED AT:

• HIGH PRESSURE 200 ATMOSPHERES
• TEMPERATURE 450 DEGREES
• IRON CATALYST

COST:

• energy (gas and electricity)
• labour (employee wages)
• starting materials (reactants)
• equipment needed
• how quickly the substance can be created

FACTORS AFFECTING COST: 

• pressure required
• temperature required
• catalyst requiered
• people required to operate machinery
• unreacted material that can be recyled - REDUCES COSTS. 

ECONOMIC CONSIDERATIONS: 

rate or reaction must be high enough to produce a sufficient daily yield 

percentage yeild achieved must be high enough to produce a sufficient a daily yield

optimum conditions should be used to give the most economical reaction

• a low temperature increases yield but the reaction is too slow
• high pressure increases yield but the reaction is too expensive
• catalyst increases rate of reaction but does not change the percentage yield

COMPROMISE: 

• temperature - 400 degrees
• iron catalyst
• pressure -200 atmospheres 

What are Fertilisers? 

• Chemicals that farmers use to provide plants with essential elements (NPK)
• Crops grow faster, bigger and increase crop yield
• Fertilisers must be SOLUBLE in water so they can be ABSORBED by the roots of the plants in solution. 

Fertilisers can be made from a neutralising reaction. (ACID + ALKALI) 

• AMMONIUM SULPHATE --> AMMONIA + SULFURIC ACID
• AMMONIUM NITRATE --> AMMONIA + NITRIC ACID
• AMMONIUM PHOSPHATE --> AMMONIA + PHOSPHORIC ACID
• POTASSIUM NITRATE --> POTASSIUM + NITRIC ACID

More on Fertilisers: 

• Increases crop yield
• replaces essential elements in the soil that have been used up by previous plants
• Or basically increasing the amount of elements present
• they provide nitrogen in the form of soluble nitrates which are used by plant to make protein for growth. 

Percentage Mass Equation:

Percentage Mass = (Mass of element / Relative formula Mass) x 100 

Careless use of fertilisers can cause streches of nearby water to become stagnant very quickly. 

1) Fertilisers are washed in to lakes and rivers. This increases the amount of Nitrogen and Phosphates. This increases the growth of simple algae

2) The algae bloom blocks off the sunlight to other plants, causing them to die out. 

3) This leads to massive increase in the number of aerobic bacteria (which feed on dead organisms), which quickly use up all the oxygen. Eventually, oxygen is removed. The larger organisms such as fish and other aquatic animals suffocate because oxygen becomes scarce. 

1) measure alkali (potassium hydroxide) into basin using measuring cylinder

2) add acid (nitrate acid) from a burette. use a glass rod to put a drop of solution on to indicator paper to test the pH. continue to add acid until it turns neutral

3) evaporate the solution, until crystals form on the end of cold glass rod

4) filter to seperate the crystals from solutoin

5) remove the crystals, wash them and leave them to dry

• The pH scale of a solution can be determined by using universal indicator. 
• You add a few drops of this in to the solution to the substance. The colour will change, compare this colour to the pH scale colour chart. 
• Bases are the oxides and hydroxides if metals. The bases that are soluble are called alkalis.
• NEUTRALISATION: ACID + BASE --> SALT AND WATER
• metal oxides and metal hydroxides neutralise acids because they are basses
• carbonates neutralise acids to give water, a salt and carbon dioxide
• acids contain HYDROGEN ions
• alkalis contain HYDROXIDE ions
• IONIC EQUATION: H+ + OH- --> H2O