C3 9-16

Question 1

What is the difference between predicted yield and actual yield?

Answer 1

The predicted yield is the expected mass calculated using
reacting masses.

The actual yield is the mass of product made.

Question 2

How do you work out percentage yield ?

Answer 2

percentage yield = actual yield × 100
predicted yield

Question 3

Why might percentage yield be less than 100%?

Answer 3

Very often, product is lost during handling and purification. It may be lost in
• filtration
• evaporation
• the transfer of liquids from one container to another
• heating.

Question 4

What is atom economy?

Answer 4

a way to measure the amount of atoms that are wasted when a certain chemical is made.

Question 5

What is the formula for atom economy?

Answer 5

atom economy = Mr of desired product X 100

Total Mr of all products

Question 6

What is the difference between endothermic and exothermic reactions?

Answer 6

For an exothermic reaction, the amount of energy taken in to break bonds is less than the amount of energy released to make new bonds.
For an endothermic reaction, the amount of energy taken in to break bonds is more than the amount of energy released to make new bonds.

Question 7

What do exothermic reactions do? Example?

Answer 7

Exothermic reactions transfer energy to the surroundings, usually as heat. If the temperature of the reaction mixture and its container goes up, the reaction is an exothermic one. Combustion is an example.

Question 8

What do endothermic reactions do? Example?

Answer 8

take in energy during the reaction. They absorb energy from the surroundings, usually as heat. If the temperature of the reaction mixture and its container goes down, the reaction is an endothermic one. Sherbet sweets are an example.

Question 9

When does an endothermic process happen?

Answer 9

when ammonium nitrate dissolves in water. The temperature may fall so much that a drop of water can freeze the container to a block of wood.

Question 10

What is calorimetry?

Answer 10

a method used to measure the energy transferred in chemical reactions.

Question 11

Describe the process of calorimetry?

Answer 11

The fuel is put into a spirit burner. This is a container with a lid, and a wick so that the fuel can be lit. The whole spirit burner is weighed. A calorimeter is filled with a known mass of water. It is then clamped above the spirit burner. The temperature of the water is measured. The wick is lit so the flame warms up the water. The lid is put back on at the end of the experiment. This puts the flame out. The spirit burner is weighed again, and the temperature of the water is also measured.

Question 12

What is a continuous process?

Answer 12

Bulk chemicals are needed in large amounts. They are usually made in continuous processes in which the product is made all the time.

Question 13

What is a batch process?

Answer 13

A product made in a batch process is not made all the time. In the chemical industry, speciality chemicals are high value chemicals needed in small amounts. They are made on demand when a customer needs them. Pharmaceuticals and other speciality chemicals are made in batch processes.

Question 14

Batch vs Continuous?

Answer 14

Pro batch
- low cost of equipment

Pro continuous

• high rate of production
• rare shut down times
• small workforce needed
• high ease of automating the process

Question 15

What are the steps to extract chemicals from plants?

Answer 15

1. Crush the plant material
2. Dissolve in a suitable solvent and filter
3. Boil to evaporate the solvent
4. Separate the chemical by chromatography

Question 16

What are the factors involved when creating a new drug?

Answer 16

• research and testing (make sure they are safe and effective )
• labour costs
• energy costs ( fuel and electricity )
• raw materials ( may be rare or expensive )
• time taken for development
• marketing ( healthcare professionals need to be informed on how to use drug )

Question 17

What are the steps of testing a drug?

Answer 17

1 - computer simulations and tests on cells grown in the laboratory.

2. The most promising substances are then tested on laboratory animals.
3. If it passes, substance is checked for side effects in healthy human volunteers.
4. It is then tested on a small group of patients to see if it works as expected, and then on a larger group of patients to gather more information about it.

Question 18

Why do some companies apply for a patent?

Answer 18

This prevents other companies making and selling the drug for up to 20 years. Once the patent expires, these companies are free to make and sell the drug.

Question 19

How do you test for impurities?

Answer 19

by measuring its melting or boiling point. Impurities alter the temperature at which a drug melts or boils. The further the temperature is away from the correct one, the less pure the drug is.

Question 20

What is thin layer chromatography?

Answer 20

can be used to see how pure a drug is. different substances move through a thin layer of powder coated onto a glass or plastic plate. Colourless substances show up as spots on the plates when reacted with certain chemicals. These may be fluorescent under ultraviolet light, or they may become coloured when heated.

Question 21

Properties and uses of diamond?

Answer 21

• Insoluble in water
• Do not conduct electricity.
• hard
• high melting point

So uses -> drill bits, glass cutters and some dental drills

• colourless and transparent
• can be cut into shapes that allow light to pass through in such a way that they seem to sparkle.

So uses -> This lustrous appearance makes them highly valued gemstones for jewellery.

Question 22

Properties and uses of graphite?

Answer 22

• black
• lustrous
• opaque
• soft and slippery
• good electric conductor

Uses -> Pencils- The black slippery graphite easily wears away on paper, leaving a black line. Graphite’s properties also make it useful in lubricants that work at high temperature.

Question 23

Structure of diamond and graphite

Answer 23

• The carbon atoms in diamond and graphite are joined to each other by covalent bonds. This is why the two substances have high melting points. A lot of energy is needed to break the covalent bonds.
• Graphite has a layered structure in which each carbon atom is joined to three others by covalent bonds. There are only weak forces between the layers, so the layers can slide over each other easily. This is why graphite is slippery.
• In diamond, each carbon atom is joined to four other carbon atoms. There are no free electrons, so diamond cannot conduct electricity.

Question 24

Describe the structure of a buckminster fullerene

Answer 24

Each molecule has 60 carbon atoms, forming a hollow sphere.

Question 25

What is an allotrope? 3 allotropes of carbon?

Answer 25

Allotropes are forms of an element that exist in the same state but have different properties because their atoms are arranged differently.

E.g diamond, graphite , fullerenes

Question 26

How can fullerenes be used for drug delivery?

Answer 26

Buckminster fullerene and other fullerenes are hollow. The space inside is large enough to contain atoms or other molecules. Scientists have found ways to cage radioactive metal atoms and drug molecules inside them. They can be coated with chemicals that cause them to gather next to cancer cells after being injected into the body. In this way, the drug can be delivered to its target without damaging normal cells.

Question 27

What are nanotubes? Structure? Conductivity ?

Answer 27

Fullerene molecules can be joined together to make nanotubes. Nanotubes are the strongest and stiffest materials yet discovered.
Nanotubes have electrical properties. Depending on their structure, nanotubes can conduct electricity like tiny wires, or act as semiconductors for electrical circuits. It is difficult to manufacture nanotubes for electrical uses at the moment.

Question 28

How can nanotubes be used as catalysts?

Answer 28

catalysts, especially when they are stacked side by side. They have a huge surface area compared to their volume, allowing a high collision frequency with reactant molecules. Their properties are modified to make them effective catalysts by attaching other substances, such as nitrogen or iron, to their surface.