Chemistry in society Flashcards
(23 cards)
Give three examples of products industry produces which make our lives easier
- Fuels (eg petrol for cars, diesel for trains & kerosene for aircraft)
- Plastics (eg nylon for clothing, paint etc.)
- agrochemicals (eg fertilisers, pesticides etc.)
What is the process for chemical industry?
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)
What is the general pattern for chemical production?
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)
What are the two forms of chemical processing?
Batch and continuous
Advantages of continuous
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.
How does batch processing work?
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.
How do you calculate % yield?
Actual yield
————————- x 100
Theoretical yield
How do you calculate Atom economy?
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
Describe the 5 steps to calculate the volume, concentration or mass of compounds
- Write balanced equation (unless already given)
- Identify the mole ratio of the two chemicals in question
- Calculate, usually moles, of substance with most info
- Use ratio in 2. to work out no. of moles other substance
- Calculate the volume, concentration or mass of the chemical you have been asked to find out
When finding which reactant is in excess…
…compare the moles of each (remember molar ratio)
Equation for molar volume?
Mv=v/n
What is molar volume and when would you use it in calculations?
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
How would you compare gases?
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
What is it important to remember when identifying oxidising and reducing agents?
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
What is the best way of identifying a redox equation?
Look for the equation (if multiple choice) where a metal is changing from an element to a compound or vice versa
Name a powerful oxidising agent and a powerful reducing agent
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
Give everyday uses for two oxidising agents
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
What does separation in chromatography usually depend on?
- Size of the molecules
2. Polarity of the molecules
Components with the greater retention time…
…usually are the biggest or the least/most polar molecule (depending on the solvent)
If the solvent in chromatography is non-polar then which compounds are likely to have the smallest retention time?
Small non-polar compounds
If a solution has a known concentration, what is it also known as?
A standard solution
Describe the steps in making a standard solution
- Accurately weigh solute
- Dissolve in small amount of solvent, warm if needed
- Transfer to standard flask
- Rinse all solution into flask with more solvent
- Carefully make up to mark of flask
- Insert stopper and shake
What is important to remember about redox equations?
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
