Chemistry in society

Question 1

Give three examples of products industry produces which make our lives easier

Answer 1

1. Fuels (eg petrol for cars, diesel for trains & kerosene for aircraft)
2. Plastics (eg nylon for clothing, paint etc.)
3. agrochemicals (eg fertilisers, pesticides etc.)

Question 2

What is the process for chemical industry?

Answer 2

Availability of raw materials
Carry out a research study
scale up production
large scale production with a chemical plant being built
Early production will be followed by careful planning
(research, pilot, plant, scaling up, production then review)

Question 3

What is the general pattern for chemical production?

Answer 3

Reactants/Feedstock -> Mixer (to get proportions right) -> Reaction vessel -> Separator based on fractionation, filtration, condensation etc. -> Product, by-product & excess reactant (which gets placed back in reaction vessel)

Question 4

What are the two forms of chemical processing?

Answer 4

Batch and continuous

Question 5

Advantages of continuous

Answer 5

can more readily be operated by a very small workforce in control rooms remote from the chemical reactors.
Product quality can be more carefully monitored and remedied if necessary.
Energy efficiency is usually good since there is rarely a need to shutdown this sort of plant.

Question 6

How does batch processing work?

Answer 6

Used to make substances that are used in small quantities by the end user (eg medicines and dyes).
Feed stocks are more likely to be recognisable as scaled up versions of processes one might carry out in the lab.

Question 7

How do you calculate % yield?

Answer 7

Actual yield
————————- x 100
Theoretical yield

Question 8

How do you calculate Atom economy?

Answer 8

Mass of desired product from equation/total mass of products from equation X 100

Mass of desired product from equation/total mass of reactants from equation X 100

Question 9

Describe the 5 steps to calculate the volume, concentration or mass of compounds

Answer 9

1. Write balanced equation (unless already given)
2. Identify the mole ratio of the two chemicals in question
3. Calculate, usually moles, of substance with most info
4. Use ratio in 2. to work out no. of moles other substance
5. Calculate the volume, concentration or mass of the chemical you have been asked to find out

Question 10

When finding which reactant is in excess…

Answer 10

…compare the moles of each (remember molar ratio)

Question 11

Equation for molar volume?

Answer 11

Mv=v/n

Question 12

What is molar volume and when would you use it in calculations?

Answer 12

The volume of 1 mole for any gas is the same, provided the temperature and pressure are constant. You would use molar volume in calculations involving gases

Question 13

How would you compare gases?

Answer 13

Remember volume is same at constant pressure and temp, therefore, if N2 + 2O2 = 2NO2 (all gases) then 10 litres of N2 would react with 20 litres of O2 to produce 20 litres of NO2

Question 14

What is it important to remember when identifying oxidising and reducing agents?

Answer 14

An oxidising agent accepts electrons and is itself reduced
A reducing agent donates electrons and is oxidised

Reducing agents have low electronegativity values
Oxidising agents have high electronegativity values

Question 15

What is the best way of identifying a redox equation?

Answer 15

Look for the equation (if multiple choice) where a metal is changing from an element to a compound or vice versa

Question 16

Name a powerful oxidising agent and a powerful reducing agent

Answer 16

Oxidisation - Permanganate ion
Reduction - Carbon monoxide

Elements/compounds in bottom left of table are strong reducing agents
Elements/compounds in top right of table are strong oxidising agents

Question 17

Give everyday uses for two oxidising agents

Answer 17

Hydrogen peroxide I a highly effective bleach and is also used in teeth-whitening and hair products. It is also an antiseptic
Potassium permanganate is also an antiseptic and is used in aquaria to destroy bacteria and fungi that can infect fish

Question 18

What does separation in chromatography usually depend on?

Answer 18

1. Size of the molecules

2. Polarity of the molecules

Question 19

Components with the greater retention time…

Answer 19

…usually are the biggest or the least/most polar molecule (depending on the solvent)

Question 20

If the solvent in chromatography is non-polar then which compounds are likely to have the smallest retention time?

Answer 20

Small non-polar compounds

Question 21

If a solution has a known concentration, what is it also known as?

Answer 21

A standard solution

Question 22

Describe the steps in making a standard solution

Answer 22

1. Accurately weigh solute
2. Dissolve in small amount of solvent, warm if needed
3. Transfer to standard flask
4. Rinse all solution into flask with more solvent
5. Carefully make up to mark of flask
6. Insert stopper and shake

Question 23

What is important to remember about redox equations?

Answer 23

They are considered self indicating.
Eg Permanganate/Iron titration purple colour of permanganate is used to judge end-point as solution will remain colourless until all iron (II) ions have reacted with permanganate ions