What is the formula of sulphuric acid?
What is the formula of calcium chloride?
What is the formula of magnesium chloride?
What is the formula of magnesium sulphate?
Which two factors detirmine the rate of reaction?
1. The collision frequency of reacting particles.
2. The energy transfered in each of the collisions (i.e. whether each collision is effective/successful).
In terms of the reacting particle model, why does increasing the temperature increase the rate of reaction?
1. At a higher temperature, the particles are vibrating and moving more quickly. As a result, it is more likely that they will collide.
2. Furthermore, the increased temperature mean that the particles are moving with a greater amount of energy. Therefore, particles will be colliding with greater energy, meaning there will be more successful collisions per second.
In terms of the reacting particle model, why do increases in concentration cause the rate of reaction to increase?
1. If the concentration is increased, there will be more particles of react in the same volume of solution.
2. Therefore, it is more likely that particles will successfully collide with eachother each second.
In terms of the reacting particle mode, why do increases in pressure result in an increase in the rate of reaction?
1. If the pressure is greater, the particles are more crowded and closer together.
2. As a result, they are more likely to collide with eachother.
What is a catalyst?
A substance that increases the rate of reaction without being chemically changed in the reaction.
There are specific catalysts for specific reactions, and catalysts are usually only needed in small quantities.
Why do catalysts increase the rate of reaction?
1. They provide a surface for the reacting particles to stick to.
2. This reduces the energy needed by aprticles to react.
3. As a result, the number of successful collisions increases.
Why do powdered substances react faster than large solids/lumps?
1. Chemicals made up of smaller pieces (e.g. powders) have a greater total surface area.
2. As a result, particles have a greater area to collide with.
3. Therefore, there will be more successful collisions every second.
4. So, rate of reaction increases.
Why are fine powders of combustible material dangerous to handle in factories?
1. Fine powders have very large surface area, so they combust extremely quickly.
2. As a result, a single spark can cause a huge explosion.
3. Factories need to be very careful when handling custard powder, flour and powdered sulfur.
What is meant by the principal of the conservation of mass?
The total mass of the reactants at the start of the reaction is equal to the total amount of product made at the end of the reaction.
What is percentage yield?
The amount of product made (actual yield) compared to the amount of scientifically predicted prodcut made (predicted yield).
percentage yield = actual yield (grams) / predicted yield (grams) * 100
Why is percentage yield usually less than 100%?
- Loss in filtration.
- Loss in evaporation.
- Loss in transferring liquids.
- Not all reactants react to make product (other/different/unintended reactions happening)
What is atom economy?
The amount of desired product produced compared to the total amount of product produced.
atom economy = total Mr of desired products / total Mr of all products * 100
Why do manufacturers want high percentage yields?
- To reduce wastage of reactants
- To reduce costs (and increase profits)
Why do manufacturers want a high atom economy?
- To reduce the production of unwanted products, therefore reducing the amount of waste material that needs to be disposed.
- By reducing wastage, the process becomes more sustainable.
Describe a simple calorimetric method for comparing the energy transferred in combustion reactions:
1. Spirit burner or bottled gas burner used
2. Water heated in copper calorimeter
3. Fuel is weighed before and after. Mass of fuel burnt recorded.
4. Temperature change measured.
5. Fair and valid test carried out.
How can the purity of drugs be tested?
1. Pure substances won't be separated by chromatography - it'll all move as one blob.
2. Pure substances have a specific melting and boiling point. Therefore, if the substance is impure, it will have a melting lower and a boiling point higher than expected.
Explain why batch processes are used to make pharmaceutical drugs but continuous processes are used to produce chemicals such as ammonia.
- Involve skilled labour-intensive work which can't be automated.
- Low demand, so less needed.
- Product needed all year round.
- It can be automated as not very labour intensive.
Describe the advantages and disadvantages of batch and continuous manufacturing.
- Flexible (different products can be made using same equipment).
- Start-up costs are relatively low
- It is labour intensive; equipment needs to be manually controlled.
- It can be tricky to produce the exact same product over and over again.
- Production never stops; time not wasted restarting reaction.
- It runs automatically; lower labour costs.
- Quality of product is consistent.
- Start-up costs are huge, and not cost efficient if not being ran at full capacity.
Why is it expensive to make and produce drugs?
- Huge research and development costs; highly-paid scientists need to find correct chemical compound.
- Trialling; lengthy human and animal trials need to be carried out. Legal requirements need to be met.
- Manufacturing by batch is labour-intensive and can't be automated.
- Raw materials from plants can sometimes be expensive.
Explain why it is difficult to test and develop new pharmaceutical drugs that are safe to use.
1. Strict legal requirements need to be made.
2. Lengthy animal and human trials need to be carried out; extremely expensive.
3. If drug has unwanted side effects, the whole investment may have been wasted.
4. Many years of testing needed to check for long-term impacts.
Describe how chemicals are extracted from plant sources:
1. Plant material is crushed.
2. Next, it is boiled and dissolved in a suitable solvent.
3. Finally, chromatography strip is used to separate the different chemicals.
Why are diamond, graphite and fullerenes, all allotropes of carbon?
They are just different structural forms of carbon.
Why is diamond used in cutting tools and jewellery?
- In a diamond, each carbon atom is bonded with four other carbon atoms in a giant covalent structure. This rigid covalent structure is what makes the diamond extremely hard.
- The strong covalent bonds take a lot of energy to break, giving diamond a very high melting point. This is also why it's useful as a cutting tool.
- Diamonds are lustrous and colourless.
Why doesn't diamond conduct electricity?
It is has no free (delocalised) electrons.
Why is graphite used in pencil leads and lubricants?
1. Each cabron atom only forms three covalent bonds, creating sheets/layers of carbon atoms that can slide over eachother.
2. There are weak intermolecular forces between these laywers, meaning they can be rubbed off onto the paper to leave a black mark.
3. The 'slipperyness' of graphite makes it great for use as a lubricant for reasons described above.
Why does graphite have a high melting point?
Graphite contains lots of strong covalent bonds. Lots of energy is needed to break these bonds, meaning that graphite has a high melting point.