Science - Chemistry - Quantitative Chemistry - Atom Economy And Yield - C3c

Question 1

what is the atom economy of a reaction ?

Answer 1

the atom economy of a reaction tells you what percentage of the mass of the reactants ends up as useful products when manufacturing a chemical

Question 2

what does 100 % atom economy mean ?

Answer 2

all the atoms in the reactants have been turned into useful products

Question 3

how do you calculate atom economy ?

Answer 3

relative formula mass of desired products / relative formula mass of all reactants X100

Question 4

how do you calculate the percentage of ‘wasted’ product in atom economy ?

Answer 4

subtract the atom economy from 100

Question 5

what is ‘wasted’ product ?

Answer 5

anything that isn’t in a desired product during a reaction

Question 6

what is the atom economy of reactions that only have one product ?

Answer 6

100 %

Question 7

why is the atom economy of reactions with one product always 100 % ?

Answer 7

all the reactants end up in the useful product

Question 8

what are the economic advantages of having a high atom economy ?

Answer 8

• reactions with low atom economies are less profitable
• produces less waste
• more of the materials going into the reaction are being used well

Question 9

what are the environmental advantages of having a high atom economy ?

Answer 9

• fewer raw materials are used
• produce less waste
• more sustainable

Question 10

what is a theoretical yield ?

Answer 10

the amount you would get if all the reactants formed the desired products, and none of the products are lost

Question 11

what is a yield ?

Answer 11

the amount of product you actually get in the product

Question 12

what is the percentage yield ?

Answer 12

a comparison between the theoretical yield and the yield you actually get

Question 13

what does a 100 % percentage yield mean ?

Answer 13

you got all the product you expected to get

Question 14

what does a 0 % percentage yield mean ?

Answer 14

no reactants were converted into product, no product at all was made

Question 15

how do you calculate the percentage yield ?

Answer 15

mass of product actually made (g) / maximum theoretical mass of product (g) X100

Question 16

why are percentage yields never 100% ?

Answer 16

because some product or reactant always gets lost along the way

Question 17

what are the 3 main problems when losing product in an experiment ?

Answer 17

1. the reaction is reversible
2. product is lost when it’s separated from the reactants
3. unexpected reactants may be happening

Question 18

how can the reaction be reversed ?

Answer 18

if a reaction is reversible, reactants will never be fully converted to products as the reaction goes both ways as some of the products are always reacting together to change back to the original reactants

Question 19

what is a reversible reaction ?

Answer 19

where the products of the reaction can themselves react to produce the original reactants

Question 20

what are the factors you need to consider when choosing which reaction use to make a substance on an industrial scale ?

Answer 20

• atom economy
• yield
• rate of reaction
• equilibrium position
• usefulness of by - products

Question 21

what is the equilibrium position ?

Answer 21

the point at which the rates of the forward and backward reactions in a reversible reaction are the same, so the amounts of reactants and products in the reaction container don’t change