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Starter:. National 5 Chemistry. Unit 3 Chemistry in Society Key Area 3 Fertilisers. Date Fertilisers. Learning Intentions I know that fertilisers provide the essential elements, nitrogen, phosphorus and potassium, that are needed for healthy plant growth
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National 5 Chemistry Unit 3 Chemistry in Society Key Area 3 Fertilisers
Date Fertilisers Learning Intentions • I know that fertilisers provide the essential elements, nitrogen, phosphorus and potassium, that are needed for healthy plant growth • I can name the catalyst used in the Haber Process • I can write the balanced equation for the Haber Process • I can name the reactants in the Ostwald process • I can work out the percentage composition of a fertiliser
Fertilisers • Growing plants require nutrients, including compounds containing nitrogen, phosphorous or potassium. (NPK) • These can be found in fertilisers
Fertilisers are……… • Fertilisers are substances which restore elements, essential for healthy plant growth, to the soil.
Photosynthesis • Plants produce their own glucose during photosynthesis. • To be able to photosynthesise efficiently, plants need nutrients from the soil • Nutrients are taken in through the roots so, Nutrients must be soluble in water
A Lack of Nutrients affects a plant’s ability to photosynthesise………………………
Lack of Nitrogen 1) Reduced root mass 2) Smaller leaf size 3) Lower leaves turn yellow and die from the tip back
Lack of Potassium • Yellowing of the leaf edges
Lack of Phosphorus • Purple coloration on the underside of the leaves. • In severe deficiencies the plant will be stunted, leaves will turn upward and show purpling of the leaves.
Types of Fertilisers • Growing plants use up nutrients from the soil • Fertilisers can be natural or Synthetic
Natural Fertilisers • Plant compost • Animal manure • Lightning • Nitrogen Fixing Bacteria in the nodules of some plants
Nitrogen in Air Lightning Ooo aaar Fertilizer !! Decaying Plant and Animal Waste Nitrogen Fixing Bacteria
Adding Nitrogen to the Soil • Manure and dead plants and animals decay to release nitrates • Legumes – peas, beans, clover contain bacteria that “fix” nitrogen into nitrates • Lightning flash combines N2and O2 to produce NO2which dissolves in rainwater
Problem • Increasing human population needs more food than natural fertilisers can provide
Artificial Fertilisers • These are man-made compounds which contain water soluble compounds • These compounds are taken up by the roots of plants • The farmer can chose specific fertilisers to replace nutrients that are missing from his soil
Starter: Calculate the percentage of: • Oxygen in Al(OH)3 • Nitrogen in Mg3N2
Ammonia and Nitric Acid • Ammonia and nitric acid are important compounds used to produce soluble, nitrogen-containing salts that can be used as fertilisers. • Ammonia is a pungent, clear, colourless gas which dissolves in water to produce an alkaline solution.
Ammonia solutions react with acids to form soluble salts. • ammonia solution + an acid → an ammonium salt + water
The Haber Process • Ammonia (NH3) is an essential starting point for the production of synthetic fertilisers. • Diatomic nitrogen in the air has a triple covalent bond holding the atoms together. • This requires a large amount of energy to break, so the direct reaction of nitrogen to hydrogen is not usually possible. • The Haber Process overcomes these difficulties.
The Haber Process Nitrogen + Hydrogen ⇋ Ammonia N2(g) + 3H2(g) ⇋ 2NH3(l) • The double arrow tells us that the reaction is reversible. • This is a problem because, as the ammonia is made, it easily breaks down into the reactants nitrogen and hydrogen again.
The Haber Process • To make this process economic and efficient, the following conditions apply………… Temperature – A Moderate temperature is used At low temperatures the forward reaction is too slow to be economical. If the temperature is increased, the rate of reaction increases but, as the temperature increases, the backward reaction becomes more dominant.
The Haber Process Pressure A High pressure is used. This increases the yield of ammonia.
The Haber Process Catalyst • An Iron (Fe) catalyst speeds up the production of ammonia, saving energy costs. • LEARN THIS
The Haber Process Condenser • This cools the reaction down, turning ammonia into a liquid which is easier to extract.
The Haber Process Recycled reactants • Unreacted nitrogen and hydrogen are returned to the reaction, saving money.
Learning Intentions and Success Criteria • Learning Intentions • To learn about the Ostwald process • To learn about percentage composition of fertilisers • Success Criteria • I can state the reactants and products of the Ostwald process • I can calculate the percentage composition of fertilisers
Ostwald Process • Ammonia is the starting material for the commercial production of nitric acid. (Ostwald process) • The Ostwald process uses ammonia, oxygen and water to produce nitric acid. A platinum catalyst is used in this process.
Steps in the Production of Nitric Acid (Ostwald Process) • Ammonia + Oxygen → nitrogen monoxide • Nitrogen monoxide + Oxygen → Nitrogen dioxide • Nitrogen dioxide + Oxygen + water → Nitric acid
Percentage Composition of fertilisers It is useful to be able to calculate exactly what proportion of essential nutrients are present in in a fertiliser. The process is exactly the same as calculating the percentage composition of a metal ore……..
Learn This Formula………. % = total mass of element X 100 total mass of the compound
Example 1What is the percentage of Nitrogen in the fertiliser ammonium nitrate? (NH4NO3) Total mass = 80g
Example 1What is the percentage of Nitrogen in the fertiliser ammonium nitrate? (NH4NO3) % of Nitrogen = total mass of element X 100 total mass of the compound
Example 1What is the percentage of Nitrogen in the fertiliser ammonium nitrate? (NH4NO3) % of Nitrogen = 28 X 100 80
ExampleWhat is the percentage of Nitrogen in the fertiliser ammonium nitrate? (NH4NO3) % of Nitrogen = 35%
Date Chemical Analysis • Learning Intentions • To know about some of the ways chemists can monitor our environment and ensure it remains healthy and safe
What would you use the following for? • conical flask • beaker • measuring cylinder • delivery tube • dropper • test tubes/boiling tubes • funnel • filter paper • evaporating basin • pipette with safety filler • burette • thermometer
Could you do the following? • Simple filtration using filter paper and a funnel to separate the residue from the filtrate • Use a balance • Methods for the collection of gases including: • collection over water (for relatively insoluble gases) • downward displacement of air (for soluble gases that are less dense than air) • upward displacement of air (for soluble gases that are more dense than air)
Methods of heating using Bunsen burners and electric hotplates • Preparation of soluble salts by the reaction of acids with metals, metal oxides, metal hydroxides and metal carbonates • Preparation of insoluble salts by precipitation • Testing the electrical conductivity of solids and solutions
Setting up an electrochemical cell using a salt bridge and either metal or carbon electrodes • Electrolysis of solutions using a d.c. supply • Determination of Eh
Testing Gases • Simple tests can be used to identify oxygen, hydrogen and carbon dioxide gases.
Titration • A titration can be used to determine accurately, the volumes of solution required to reach the end-point of a chemical reaction. • An indicator is normally used to show when the end-point is reached. • Titre volumes within 0·2 cm3 are considered concordant. • Solutions of accurately known concentration are known as standard solutions.
Activity 10.b Titrations • In a titration a pipette is used to transfer a known volume of acid or base into a conical flask. An indicator is then added to the conical flask. The indicator allows the end point of the titration to be easily observed. • A burette is filled with acid or base of a known concentration. • The burette is then used to accurately add known volumes of acid or base into the conical flask. When a colour change is observed, the reaction has reached its end point.
