Flashcards in C2 9-16 Deck (31):
Factors you need to consider when manufacturing something?
- Cost of starting materials
- Cost of the equipment needed
- Labour costs and wages
- Price of the energy needed
- The speed at which the new substance is made
Uses of ammonia?
It is often used in cleaning fluids because it reacts with grease, making this easier to remove. It has other uses too, including making nitric acid and fertilisers. For example, ammonia and nitric acid react together to make ammonium nitrate, which is an important source of nitrogen in artificial fertilisers.
What are fertilisers?
Fertilisers are substances applied to the soil to replace minerals used up by plants. Without fertilisers, crop yields would be much smaller. Fertilisers are so important to world food production that they use around 80% of all the ammonia manufactured.
Explain the Haber process?
Ammonia is made from nitrogen and hydrogen
nitrogen + hydrogen (=) ammonia
N2 + 3H2 (=) 2NH3
The hydrogen often comes from cracking oil fractions or from natural gas. The nitrogen comes from air. Nitrogen is a relatively unreactive gas, so the conditions needed to get it to react with hydrogen must be
• a high pressure
• a temperature of around 450 °C
• adding an iron catalyst to speed up the reaction.
What are the signs of a chemical change?
- a new substance produced
- irreversible change
What is the yield?
The amount of a substance made in a reaction
What do the conditions in the Haber process mean?
- The higher the pressure, the greater the percentage yield of ammonia. ( not too high -> expensive equipment )
- catalyst + high temp -> sufficient daily yield
What do acids to when they dissolve in water?
Produce acidic solutions. These contain hydrogen ions, H+.
What does a higher concentration of H+ ions mean?f
It is more strongly acidic, and the lower its pH
What is an indicator?
An indicator is a substance that changes colour depending on whether it is in an acidic or an alkaline solution. Litmus is an indicator that shows a sudden change in colour. It is red in acids and blue in alkalis. Litmus cannot show how acidic or alkaline a solution is, but universal indicator which is a mixture of different indicators. Each one changes colour over a different pH range. This means that the pH of a solution can be estimated.
What is a base?
a substance that can neutralise an acid
What is neutralisation?
The reaction between an acid and a base. Salt and water is produced.
General word equation for reaction between base and acid
acid + base → a salt + water
When you use a carbonate to neutralise an acid, co2 is produced too
carbonate + acid → a salt + water + carbon dioxide
What is the ionic equation for neutralisation?
H+ + OH– → H2O
How do you name salts?
The first part comes from the name of the metal in the base or carbonate. The second part comes from the acid used:
• hydrochloric acid produces chloride salts
• nitric acid produces nitrate salts
• sulfuric acid produces sulfate salts
• phosphoric acid produces phosphate salts
What are three essential elements for plant growth?
What is eutrophication?
using too much fertiliser can pollute water supplies, leading to problems such as the death of living organisms in the water.
Step by step process of eutrophication?
- fertilisers wash into river or lake
- increased nitrate or phosphate in water
- algae grow faster
- plants shaded by algae die
- aerobic decay bacteria use up oxygen
- living organisms die
How can fertilisers be made?
neutralising an acid with an alkali.
How do you produce a neutral salt solution?
A burette and measuring cylinder are used to measure the volumes of liquid . The salt solution is then heated to evaporate some of its water. This reduces the volume and makes it more concentrated. As it cools, crystals of salt form. They are separated from the solution by filtration using a filter funnel and filter paper.
Where is common salt (sodium chloride) obtained from?
- from seawater by evaporating the water.
- It can also be obtained from salt deposits. These are the remains of ancient seas that have long since evaporated and been covered by rock.
- Salt for cooking and for applying to the roads in winter is usually mined in the normal way.
What is solution mining?
Water is pumped from the surface into the deposit deep underground. The sodium chloride dissolves in the water, and the brine is pumped up to the surface. This is a continuous process that needs little labour, which keeps costs down.
What is subsidence?
the land slumps downwards because of a mine below, leading to cracked buildings and holes appearing in the ground.
What does the electrolysis of brine produce?
• sodium hydroxide solution.
What are the uses for the products of electrolysis of brine?
- Hydrogen is used in the manufacture of margarine. It is used to convert liquid vegetable oils into solid vegetable fats.
- Chlorine is used to sterilise water. It is widely used to kill harmful microorganisms in swimming pool water and tap water. PVC is made from chloroethene. Chlorine is also used to make household bleach and some solvents.
- Sodium hydroxide reacts with vegetable oils to make soap. It also reacts with chlorine to make household bleach
Equation for sodium chlorite solution? (Bleach)
Sodium hydroxide + chlorine -> sodium chloride + water + sodium chlorate
What is brine?
concentrated sodium chloride solution. It is a raw material for the chlor-alkali industry.
What is the chlor-alkali industry?
This is the chemical industry that produces useful new substances from the electrolysis of brine. Large amounts of electricity are needed, and electricity accounts for about half of the production costs.
What is electrolysis?
Electrolysis is the process in which a compound breaks down to form new substances when electricity is passed through it. Two electrodes are needed to pass the electricity into the salt solution. These are made from an inert material such as titanium. This stops the electrodes reacting with the salt or the products from it. Different products form at each electrode during electrolysis:
• chlorine forms at the positive electrode (the anode)
• hydrogen forms at the negative electrode (the cathode).
Sodium hydroxide is also mad
What is oxidation and reduction?
Oxidation is the gain of oxygen
reduction is loss of oxygen by a substance. can also be
• oxidation is loss of electrons
• reduction is gain of electrons.