Salt
- Salt can also add flavour to food
- Salt was once needed as a preservative to make food last longer - we call this ‘shelf life’
- We now have fridges, freezer and cans to make food last a long time
- People who make our food adds to much salt
- 75% of the salt you eat is added into the food you eat
- Eating less salt is the best way to prevent high blood pressure when you get older
- Effects: stomach cancer, obesity, heart attacks, osteoporosis and kidney disease
- 1g of sodium = 2.5g of salt
Making Alkalis
Explain how the process for making alkalis has changed
Sodium Hydroxide + Hydrochloric Acid = Sodium Chloride (Salt) + Water
Notes
- The process to make sodium carbonate is called the leblanc process
- Makes1 tonne of alkalise solid waste
- Nicholas Leblanc is a french chemist who invented making an alkali from salt and limestone
- Every time salt is used, tonnes of coal were burned
- Hydrogen Chloride, from factory chimneys, dissolved in rainwater to provide acid rain
- Developing new methods for manufacturing alkalis
- Hydrogen Chloride gas is oxidised to provide chlorine, a useful product
- Henry Deacon’s process: mix hydrogen chloride with oxygen and let the gases flow over a half a catalyst. The products were Chlorine and Steam
In the periodic table, the elements are arranged in rows, one above the other. Each row is a period. The most obvious repeating pattern is from the metals on the left to non metals on the right.
Each column is a group of similar elements
Group one are alkali metals
Most metals are dense and have a high melting point
Lithium, Sodium & Potassium have a low density, low melting point and the boiling points decrease down the group
Chemists use the term salt to cover all the compounds of metal with non metals
Alkali + Acid →Salt + Water
The reaction of potassium with water is very violent
- It was necessary to find a way to manufacture alkalis on a large scale at the end of eighteenth century because there was a high demand of alkalis to neutralise acids
- The raw materials needed in the Leblanc process were: chalk, salt and coal
- Alkali name - Sodium Carbonate
- The Leblanc process is an inefficient way of making an alkali as it produced dangerous gases and waste
- The properties of hydrogen chloride that means it is acidic and dissolves in water, which makes acid rain
- The pollution from the Leblanc process was made worse when acidic rain fell onto the solid waste, because the solid waste gave off an hydrogen sulphide gas, which let of a disgusting smell
- The things that was being done to hydrogen chloride
Electrolysis of Brine
Chlorine:
- To treat drinking water and waste water
- To make bleach
- To make hydrochloric acid
- To make plastics including PVC
- To make solvents
Sodium Hydroxide:
- To make bleach
- To make soap and paper
- To process food products
- To remove pollutants from water
- For chemical processing and products
- To make products
Hydrogen:
- To make hydrochloric acid
- As a fuel to produce steam
Halogens - as you go down group 7, the elements are less reactive
Chlorine:
- Smelly and poisons
- Pale green gas
- melting point 101.C
- Boiling point 35.C
Bromine:
- Smelly and poisons
- Deep red liquid
- Melting point -7.C
- Boiling point 184.C
Iodides:
- Smelly and harmful
- Melting point 144.C
- Boiling point 184.C
Covalent bonding means atoms are willing to lose electron and sharing orbital shells to form the correct orbital. Oxygen is a gas as it has plenty of energy to spread around and bounce off of other molecules, the two atoms never separate as they have strong bonds
Hydrosphere
When salt dissolves and conducts electricity, the water molecules come in between the sodium and chloride molecules causing them to spread and being able to move.
- All nitrates are double
- All salts of sodium and potassium are soluble
- Silver chloride is insoluble
- Silver bromide is insoluble
No comments:
Post a Comment