Samenvatting - Chemical ideas

• 1 Agriculture and Industry

• How do you calculate the atom economy?

  (Mr of useful product/ Mr of reactants) x 100

• How would you calculate percentage yield?

  (actual mass/theoretical mass) x 100

• 1.1 Green chemical process

• What are potential benefits of using a certain industrial method?

  - high percentage yield

  - solvent can be recycled = does not damage the environment through waste disposal 

  - no toxic products

  - high atom economy

• How can chemists help farmers improve food?

  - pesticides

  - control soil pH

• Suggest two reasons why CO isn't released into the atmosphere?

  - it's toxic

  - it can be burnt as a fuel

• What are the environmental hazards of making benzophenone? 

  - HCl is produced = toxic

  - aluminium compounds are wasted

  - benzene is toxic and hazardess 

• What are the benefits of recycling?

  - minimise waste

  - reduce energy consumption

  - reduce feedstock consumption

• What difficulties arise when recycling plastics?

  Sorting different types of plastics as they have similar properties. As a result, most recycled plastics are mixtures of different polymers.

• Why does recycling aluminium mean a large saving of emitted carbon dioxide compared to other materials e.g. glass?

  The process of extracting aluminium consumes a large amount of energy which is produced from burning fossil fuels. Less fuel is needed to recycle aluminium.

• What hazard arises when using sodamide? How is it minimised? 

  Reacts violently with water

  Keep under anhydrous conditions 

• What hazard arises when using pyridine? How is it minimised? 

  Highly flammable

  Keep in  a sealed container & incinerate excess gas 

• What hazard arises when using hydrogen? How is it minimised? 

  Explosive

  Control the rate of addition of pyridine to sodamide so the hydrogen can be incinerated in the thermal oxidiser

• What hazard arises when using ammonia? How is it minimised? 

  Toxic

  Use it in solution

• Give two advantages and two disadvantages of the batch process.

  Advantages - cost effective for small quantities

                           - range of products can be made in the same vessel

   

  Disadvantages - exothermic reactions are more difficult to control

                                 - charging and emptying the reactor is time consuming 

• Give two advantages and two disadvantages of the continuous process. 

  Advantages - suited to high tonnage production

                           - contamination risk is low

   

  Disadvantages - higher capital cost before any production can occur + not cost effective when run below full capacity

                                 - contamination risk is higher when used for two or more products

• What is the formula of ammonium sulfate?

  (NH4)2SO4

• 1.2 Bonding, structure and properties

• What type of particles do covalent network substances have?

  Atoms

• What type of particles do metallic substances have?

  positive ions surrounded by delocalised electrons

• What are the typical properties of ionic compounds in terms of Mpt/Bpt, Hardness, Conductivity, Solubility in water, Solibility in non-polar solvents?

  Mpt/Bpt = high

  Hardness = hard but brittle

  Conductivity = conducts in molten or dissolved in water

  Solubility in water = often soluble

  Solibility in no-polar solvents = generally insoluble

• What are the typical properties of covalent network compounds in terms of Mpt/Bpt, Hardness, Conductivity, Solubility in water, Solibility in non-polar solvents?

  Mpt/Bpt = very high

  Hardness = very hard 

  Conductivity = does not conduct

  Solubility in water = insoluble

  Solibility in no-polar solvents = insoluble

• What are the typical properties of metallic compounds in terms of Mpt/Bpt, Hardness, Conductivity, Solubility in water, Solibility in non-polar solvents?

  Mpt/Bpt = high (except mercury)

  Hardness = hard but malleable 

  Conductivity = conduct when solid or liquid

  Solubility in water = insoluble

  Solibility in no-polar solvents = insoluble

• What are the typical properties of simple molecular compounds in terms of Mpt/Bpt, Hardness, Conductivity, Solubility in water, Solibility in non-polar solvents?

  Mpt/Bpt = low

  Hardness = soft 

  Conductivity = do not conduct

  Solubility in water = usually insoluble, unless molecules contain groups which can hydrogen bond with water

  Solibility in no-polar solvents = usually soluble

• What type of particles do simple molecular compounds have? What are they held together by?

  Small molecules held together by weak intermolecular forces

• Explain why many ionic substances are soluble in water, naming the bonds broken and made.

  - ionic bonds broken

  - ion dipole bonds formed

  - hydrogen bonds in water are broken

  - similar strength between bonds broken and made