3.1 getting the most from reactants

Question 1

What are industrial processes designed with in mind?

Answer 1

• maximising the profit

- minimise the impact on the environment

Question 2

Factors influencing industrial process design are…?

Answer 2

• availability, sustainability and cost of feedstocks
• opportunities for recycling
• energy requirements
• marketability of by-products
• product yield

Question 3

Environmental considerations when designing an industrial process are…?

Answer 3

• minimising waste
• avoiding the use or production of toxic substances
• designing products which will biodegrade if appropriate

Question 4

Why is one reactant usually in excess?

Answer 4

so that this reactant will not control how much product is produced

Question 5

What is the limiting reactant?

Answer 5

the reactant that is not in excess and will determine how much product is produced

Question 6

How can you tell which reactant is in excess if you have calculated the number of moles of each substance?

Answer 6

taking into consideration the molar ratio, the one with the largest number of moles

Question 7

What is molar volume?

Answer 7

• the volume occupied by one mole of any gas at a certain temperature and pressure.
• the molar volume is the same for all gasses at the same temperature and pressure

Question 8

What is the equation to calculate the volume of gasses?

Answer 8

V=n x molar volume (MV)

Question 9

When comparing gas volumes what must be taken into account?

Answer 9

that one of the reactants will be in excess and the excess will be included in the final volume

Question 10

How do we compare gas volumes?

Answer 10

molar ratio

Question 11

What are percentage yield and atom economy a measure of?

Answer 11

the efficiency with which reactants are converted into the desired product

Question 12

What would decide which reactant would be in excess?

Answer 12

the less expensive reactant would be in excess to ensure that a costly reactant is converted into product

Question 13

What is theoretical yield?

Answer 13

the quantity of desired product obtained, assuming full conversion of the limiting reagent

Question 14

What is the actual yield?

Answer 14

the quantity of desired product formed under the prevailing reaction conditions

Question 15

What is percentage yield?

Answer 15

provides a measure of the degree to which the limiting reagent is converted into the desired product

Question 16

What can the percentage yield be used to calculate?

Answer 16

if the costs are given for reactants then the cost of reactants required to produce a given mass of product

Question 17

What does the atom economy measure?

Answer 17

the proportion of the total mass of all starting materials converted into the desired product in the balanced equation.

Question 18

when will reactions with a high percentage yield have a low atom economy?

Answer 18

if large quantities of by-products are formed