3 3 yield and atom economy

Percentage yield compares the actual yield to the theoretical yield.

Actual yield is the recorded amount of product obtained from a chemical reaction.

The actual yield can be determined by experiment only.

Theoretical yield is the amount of product that would be obtained under perfect practical and chemical conditions.

The type of calculation lets you determine theoretical yield is a reacting mass calculation.

The equation for percentage yield is: (actual yield theoretical yield) x 100

True. For economic reasons, the objective is to have as high a percentage yield as possible to increase profits and reduce costs and waste.

If the actual yield is 1.50 g and theoretical yield is 2.00g, the percentage yield is: (1.50 2.0) x 100 = 75%

Factors that can reduce percentage yield include:

The steps to calculate theoretical mass of products are:

The formula to calculate moles from mass is: Moles = mass / molar mass

False. Coefficients in a balanced equation are not used to calculate molar masses. Molar masses are calculated from chemical formulae.

The formula to calculate mass from moles is: Mass = moles × molar mass

False. The theoretical yield can be calculated assuming 100% conversion of reactants to products.

The molar ratio is determined by the coefficients in the balanced chemical equation.

Calculating theoretical masses of products allows for comparison with actual yields and determination of percentage yield.

Atom economy is a measure of the efficiency of a chemical reaction in terms of how well reactants are utilised to produce useful products.

Atom economy tells us what percentage of the mass of reactants become useful products.

To calculate atom economy: Atom economy =

The atom economy for N2 (g) + 3H2 (g) ⇌ 2NH3 (g) is 100% as there is only one product.

True. The higher the atom economy of a process then the more sustainable that process is

The atom economy for the production of CaO in the reaction is 56%.

The atom economy of a reaction can be increased by selling the by-products of the reaction.

The atom economy for the production of ethene is 100%.

False. Higher atom economy means less waste production.

Waste reduction in chemical processes is important because it minimises environmental impact and is more sustainable.

A lower atom economy indicates more waste production in a reaction.

Atom economy can be improved by finding uses for by-products or choosing reaction pathways with fewer unwanted products.

An atom economy of 100% indicates that all atoms from the reactants end up in the desired product.

Four factors considered when choosing a reaction pathway are:

Reactions with low atom economies are unsustainable because they use up too much raw material to manufacture only a small amount of product.

True. Fast reaction rates are desirable in industrial chemical processes.

The position of equilibrium can be changed by altering reaction conditions.

False. High percentage yields are desirable in industrial chemical processes.

Selling or reusing waste products can improve the atom economy of a reaction.

Companies continually analyse reactions and processes to improve efficiency and reduce costs.

Higher atom economy means more efficient use of raw materials and less waste production.

Alternative methods of production can improve atom economy by producing more useful by-products.