Formulas, yield and Atom Economy

Question 1

An ester is hydrolyzed as shown by the following equation.

RCOOR’ + H2O -> RCOOH (Mr=100) is obtained from 1.0g of RCOOR’ (Mr=150)?
A. 33%
B. 50%
C. 67%
D.75%

Answer 1

75%

Question 2

What are empirical and molecular formulas?

Answer 2

Ratios

Question 3

What is empirical formula?

Answer 3

The empirical formula gives just the simplest whole number ratio of atoms of each element in a compound

Question 4

What is molecular formula?

Answer 4

The molecular formula gives the actual numbers of atoms of each element in a compound

Question 5

What is the molecular made up of ?

Answer 5

A whole number of empirical units

Question 6

What two things can empirical formulas be calculated from?

Answer 6

• Percentage composition
• Experiments

Question 7

Define theoretical yield? and describe it

Answer 7

• The mass of the product that should be formed in a chemical reaction
• It assumes no chemicals are ‘lost’ in the process
• You can use the masses of reactants and a balanced equation to calculate the theoretical yield for a reaction

Question 8

Describe the actual yield

Answer 8

• The actual mass of product
• It will always be less than the theoretical yield
• Because: sometimes not all the ‘starting’ chemicals react fully, and some chemicals are always ‘lost’

Question 9

Give the formula for percentage yield

Answer 9

percentage yield= actual yield/theoretical yield x 100

Question 10

What is function of atom economy

Answer 10

The measure of the efficiency of a reaction

Question 11

What is the purpose of percentage yield?

Answer 11

• Tells you how wasteful a process is
• Based on how much of the product is lost during the process
• Doesn’t measure how wasteful a reaction is itself
• A reaction with a 100% yield could still be wasteful if a lot of the atoms from the reactants wind up in by-products rather than the desired product

Question 12

Define Atom Economy

Answer 12

The measure of the proportion of atoms that become part of the desired product in the balanced chemical equation

Question 13

What is the formula for Atom Economy

Answer 13

molecular mass of desired product/ sum of molecular masses of all reactants x 100

Question 14

Note

Answer 14

Always make sure you’re using a balanced equation

Question 15

Why do chemical industries try to use processes with high atom economies?

Answer 15

• Better for the environment because they produce less waste
• Waste that’s made needs to be disposed of safely so the less made the better
• Make more efficient use of raw materials, so they’re more sustainable
• They’re less expensive. A company using a high atom economy will spend less on separating the desired product from the waste products

Question 16

What is the importance of percentage yield

Answer 16

Idea of getting as much product as possible in the reaction/ idea of efficient conversion of reactants to products

Question 17

What is the importance of atom economy

Answer 17

Ideas of maximising the mass of reactants/ atoms that end up in desired product or ideas of minimising the amount of by-products