Unit 3 Chemistry In Society Flashcards
Name factors that influence the design of the chemical process?
- Availability, sustainability, and cost of local feedstocks
- Opportunities for recycling chemicals that were not used in the chemical process back into the reaction
- Energy requirements for the reaction
- marketability of by-products
- Product yeild
What are some environmental considerations that must be taken when designing a chemical process?
- Minimising waste
- avoiding the use or production of toxic substances
- designing products that will biodegrade, if appropriate.
What impacts might availability, sustainability, and cost of feedstocks have on a chemical process?
Profit gain: Using local feedstocks to save transportation costs
Profit loss: using feedstocks which require transportation as this has safety and environmental considerations as well as an increased cost. Availability of feedstocks will influence the price of purchase for example rare materials will cost more, and Energy created by oil and gas is subject to fluctuating prices.
What impacts might it have on a chemical process if a chemical is available to be recycled?
Profit gain: unreacted starting materials can be fed back into the process and this reduces the waste produced by the chemical process.
Profit loss: separating unreacted starting materials at the end of the reaction is costly and wasteful.
What impact does energy requirements have on the design of a chemical process?
Profit gain: Exothermic reactions can be used to provide heat for a continued reaction or to heat the plant. Catalysts can be used to speed up reactions negating the need for higher temperatures to be used as they lower the activation energy of the reaction.
However we must have considerations in place when using exothermic reactions as they have safety concerns of their own as they can cause explosions.
Profit loss: Reactions that require heat are costly due to the required cost of energy, and reactions that require cooling are also costly as they require coolants to remove energy from the reaction.
What impact does by-products of a reaction being marketable have on a reaction?
Profit gain: If additional products can be used in other processes then money will be saved. Alternatively they could be sold to other companies that could result in more profit.
Profit loss: it is expensive to deal with toxic, corrosive, or environmentally damaging by-products like sulfur dioxide or carbon dioxide.
What impact does the product yield have on the design of a chemical process?
Profit gain: High yields of product equate to large profits
Profit loss: a low yielding reaction requires several repeats to generate sufficient product. This costs businesses both time and energy.
What is the Equation used to calculate atom economy?
%atom economy = mass of desired product/total mass of reactants * 100
Why is high atom economy important for chemical industries?
High atom economy means that there will be little waste products to deal with, this reduces the costs of both separating unreacted reactants from products and means that you don’t have to take into account how you are disposing of waste products if there are’t any.
What equation do we use to calculate the percentage yield of a chemical reaction?
%yield = actual yield/theoretical yield *100
What is excess?
A term used to describe a reactant that is not the limiting factor of the reaction, in most reactions there will be some chemicals that remain in the reaction these chemicals are in excess as they are not completely used up in the reactant.
