C3 - chemical economics

Question 0

How do you calculate the rate of reaction from a graph?

Answer 0

Use the gradient

y/x

Question 1

What is the rate of reaction?

Answer 1

The rate of reaction measures how much product is formed in a fixed period of time.

Question 2

What is the limiting reactant?

Answer 2

The limiting reactant is the reactant not in excess that gets used up by the end of the reaction.

Question 3

What does ‘direct proportion’ mean?

Answer 3

The amount of product formed in a reaction is directly proportional to the amount of limiting reactant used.

Question 4

How is the ROR increased with concentration?

Answer 4

As the concentration increases the particles become more crowded. This increases the number of collisions between reacting particles.

Question 5

How does ROR increase with temperature?

Answer 5

As the temperatures increases, the particles gain kinetic energy and move around more quickly, so collisions between reacting particles are more successful and also occur in greater number.

Question 6

How does the ROR increase with pressure?

Answer 6

Increases in pressure force particles closer together, increasing the rate of reaction.

Question 7

What does the rate of reaction depend on?

Answer 7

The rate of reaction depends on the collision frequency: this describes the number of successful collisions between reacting particles each second.

Question 8

Why do some factory owners have to be very careful when using combustible powders?

Answer 8

Combustible powders can cause explosions.

• some powders react with oxygen to make large volumes of carbon dioxide and water vapour.
• the owners of a factory using combustible powders such as flour, custard powder or sulfur must be very careful. They must ensure that the powders can’t reach the open atmosphere and that the chance of a spark being produced near the powders is very small.

Question 9

Why does an increased SA of a solid increase the ROR?

Answer 9

Reactions occur when reactant particles collide with sufficient energy.

Powders can spread throughout a reaction mixture, increasing the collision frequency.

In a block material, collisions can only occur with the particles on the surface. Most of the particles in the block are trapped on the inside, so they are not available to react.

Question 10

What does a catalyst do?

Answer 10

A catalyst changes the ROR and is unchanged and the end of the reaction. Each catalyst is specific to a different reaction.

Question 11

How do you calculate the relative formula mass?

Answer 11

The relative atomic mass of elements can be found on the periodic table. Atomic mass is the largest number shown for each element; these numbers can be found above the atomic symbol in the table.

The relative atomic masses must be added up in the correct order. BIDMAS.

Question 12

Explain the conservation of mass.

Answer 12

In any chemical equation, the total mass of the reactants equals the total mass of the products. This is called conservation of mass.

Mass is conserved because atoms cannot be created or destroyed, only rearranged into different compounds.

Question 13

What is the formula for calculating percentage yield?

Answer 13

percentage yield = actual yield/predicted yield x 100

Question 14

Why do industrial processes need to have a high percentage yield as possible?

Answer 14

So that they:

• reduce the amounts of reactants wasted, which is wasteful and costly
• reduce their costs by ensuring that enough reactants are used, as too little reduces the amount of product

Question 15

What is the formula for atom economy?

Answer 15

rfm of desired products/sum of rfm of all products x 100

Question 16

Why does industry want as high an atom economy as possible?

Answer 16

• to reduce the production of unwanted products that will end to be disposed of (which often adds to overall costs)
• to make the process more sustainable by making better use of the reactants, so conserving raw materials and avoiding the need to get rid of wasted products.

Question 17

What makes a reaction endo or exo thermic?

Answer 17

Bond breaking is an endothermic process. If more energy is needed than released, the reaction is endothermic.

Bond making is an exothermic process. If more energy is released than needed, the reaction is exothermic.

Question 18

What is the formula needed to calculate the energy transferred by a fuel?

Answer 18

Energy transferred (in J) = mass of water heated (in g) x 4.2 x temperature change

Question 19

To find out the energy released by 1g of solid fuel:

Answer 19

• measure out the mass of 1g of fuel.
• pour 100g of water into a copper calorimeter (1cm cubed of water = 100g)
• heat the water with the burning fuel
• measure the temperature rise
• repeat with different fuels to ensure fair testing
• ensure reliability by repeating results

Question 20

To calculate the energy in a gram of fuel what formula would you use?

Answer 20

Energy per gram = energy released (in J) / mass of fuel burnt (in g)

Question 21

What are the advantages of continuous processing?

Answer 21

Makes large amount of the product 24 hours a day, seven days a week.

Takes place in large chemical plants with good transport links; plants are highly automated so have minimal labour costs, making the product cheaper.

Takes less energy to maintain - as long as the process can be kept running - than to start and stop the process.

Question 22

What are the advantages of batch processing?

Answer 22

Makes a fixed amount.

Allows batches to be made and stored until needed.

Allows quantities to be made that can be sold within a given time as many drugs have a ‘sell by’ date.

Makes it easy to make a new batch when needed.

Makes it easy to change production to a different product.

Question 23

What are the disadvantages of continuous processing?

Answer 23

The process is inefficient if not in constant use.

There is a very high initial building and set-up cost for these chemical plants.

Question 24

What are the disadvantages of batch processing?

Answer 24

Each batch has to be supervised so it is labour intensive and very costly.

Time is needed for cleaning if the product line is changed.

It is inefficient as the production is not in constant use.

Question 25

Why are medicines so expensive?

Answer 25

Drug prices are set to take account of the development costs.

• it can take about 10 years to develop and test a new drug and each county has strict safety laws that pharmaceutical companies must follow.
• many compounds need to be made before one may be useful to develop.
• raw materials are often rare and costly.
• many raw materials are found in plants, and are difficult to extract.

Question 26

What does extracting a chemical from a plant involve?

Answer 26

• crushing to disrupt and break cell walls
• boiling in a suitable solvent to dissolve the compounds
• chromatography to separate and identify individual compounds
• isolating, purifying and testing potentially useful compounds

Question 27

What do pure compounds have?

Answer 27

Pure compounds have definite melting points and boiling points.

Think later chromatography is used to test the purity of a compound by comparing the speed of movement against a known pure sample.

Question 28

Why is it difficult and costly to get a licence for a new drug?

Answer 28

• thousands of compounds need to be tested to find effective ones
• likely compounds need to be tested on living tissue to ensure safety
• long-term trials on humans are needed to identify possible side effects
• many similar compounds need to be developed to try and reduce side effects
• recommended doses need to be shown to be effective
• the research needs to be independently verified
• patents expire before costs are recouped and others can make a version

Question 29

What is an allotrope?

Answer 29

Allotropes are different structures of the same element. Diamond, graphite and fullerenes are all allotropes of carbon.

Question 30

What can fullerenes and carbon structures form and do?

Answer 30

Fullerenes and carbon structures that form spheres or tubes can be used:

• to carry and deliver drug molecules around the body
• to trap dangerous substances in the body and remove them

Question 31

What is the structure of a buckminsterfullerene?

Answer 31

Buckminsterfullerene contains 60 carbon atoms in a sphere. It’s formula is written as C sixty. Each sphere is measured in nanometres. A nanometre is 10 to the -9 metres long.

Question 32

Why is diamond useful?

Answer 32

Diamond is the hardest natural substance known and has a very high melting point and boiling point. The imperfections that naturally occur in diamonds form cleaving plates which allow them to be shaped. These properties make them idea for use in cutting tools and in jewellery, as the facets reflect the light.

Question 33

Why is graphite useful?

Answer 33

Graphite has a high melting point and boiling point, but the layers can slide over each other. It is used in pencils and as a high temperature lubricant.

Question 34

Properties of diamond and graphite?

Answer 34

Giant covalent bonding involves electron sharing. Every carbon atom in diamond is covalently bonded to four others in a three dimensional tetrahedral lattice with all the outer shell electrons being shared.

Question 35

What are the specific properties of diamond?

Answer 35

• strong covalent bonds in all directions make diamond hard. Large amounts of energy are required to break the bonds, giving a high melting point of 3350 degrees C.
• an absence of free elections, meaning diamond does not conduct electricity.

Question 36

What are the specific properties of graphite?

Answer 36

Every carbon atom in graphite is covalently bonded to three others in flat hexagonal layers. This formation leaves an unshared outer shell electron. This delocalised electron is free to move along the layer. The separate layers are only weakly attracted to each other.

This structure gives graphite specific properties:

• the strong covalent bonds give graphite a melting point similar to diamond.
• the delocalised elections make it a good electrical conductor.
• when force is applied, the weak forces between the layers slide over each other; this slippery nature makes it an ideal high temperature lubricant.

Question 37

Talk to me about giant molecular structures

Answer 37

Giant covalent bonding forms compounds with millions of very strong fixed bonds.

• any compound with this structure will have a high melting point
• if the bonds are formed in different directions, the substance is hard
• if the bonds form in layers, it will be easy to cut into slices
• if there are no free electrons the substance will not conduct electricity

Nanotubes can be used in catalyst systems. Atoms of the catalyst can be attached to the large surface areas on the nanotubes.