atom economy sc14b

Question 1

Recall the formula for calculating atom
economy.

Answer 1

% atom economy = molar mass of product ÷ molar mass of all reactants × 100%

Question 2

Example Q.

Hydrogen can be manufactured by reacting methane with steam:

CH4(g) + H2O(g) → 3H2(g) + CO(g)

Calculate the atom economy for the reaction.

(Ar of H = 1, Ar of C = 12, Ar of O = 16)

Answer 2

Mr of CH4 = 12 + (4 × 1) = 16

Mr of H2O = (2 × 1) + 16 = 18

Total Mr of reactants = 16 + 18 = 34

Ar of H2 = (2 × 1) = 2

Total Mr of desired product = 3 × 2 = 6 (there are three H2 in the balanced equation)

Atom economy = molar mass of product ÷ molar mass of all reactants × 100%

Atom economy = ( 6 ÷ 34 ) × 100

Atom economy = 17.6% (to 3 significant figures)

Question 3

Explain how atom economy and yield
determine the choice of reaction pathway

Question 4

Explain how the usefulness of by-products
determines the choice of reaction pathway