What does percentage yield compare?

Percentage yield compares the actual yield to the theoretical yield.

Define actual yield .

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

How is the actual yield determined?

The actual yield can be determined by experiment only.

What is theoretical yield ?

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

What type of calculation lets you determine the theoretical yield ?

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

True or False? A high percentage yield is desirable for economic reasons.

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

What factors can reduce the percentage yield of a reaction?

Factors that can reduce percentage yield include: Incomplete reactions Side reactions Loss during processing Reversible reactions.

What are the steps to calculate theoretical mass of products? (Higher tier only)

The steps to calculate theoretical mass of products are: Write balanced equation. Convert given mass to moles. Use coefficients to find moles of product. Convert moles of product to mass.

What is the formula to calculate moles from mass?

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

True or False? Coefficients in a balanced equation are used to calculate molar masses.

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

What is the formula to calculate mass from moles?

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

True or False? The theoretical yield can only be determined by experiment. (Higher tier only)

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

How do you determine the molar ratio between reactants and products?

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

What is the purpose of calculating theoretical masses of products? (Higher tier only)

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

What is atom economy ?

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

What information does atom economy give about a reaction?

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

What is the atom economy of the following reaction? N 2 (g) + 3H 2 (g) ⇌ 2NH 3 (g)

The atom economy for N 2 (g) + 3H 2 (g) ⇌ 2NH 3 (g) is 100% as there is only one product.

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

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

What is the atom economy for the production of CaO in the following reaction? CaCO 3 → CaO + CO 2 M r CaCO 3 = 100, M r CaO = 56, M r CO 2 = 44

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

How can the atom economy of a reaction be increased?

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

What is the atom economy for the production of ethene? C 2 H 2 + H 2 → C 2 H 4

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

True or False? Higher atom economy indicates more waste generation.

False. Higher atom economy means less waste production.

Why is waste reduction in chemical processes important?

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

How does atom economy relate to waste production?

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

How can atom economy be improved?

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

What does an atom economy of 100% indicate?

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

List four factors considered when choosing a reaction pathway.

Four factors considered when choosing a reaction pathway are: Atom economy Percentage yield Rates of reaction Equilibrium position

Why are reactions with low atom economies unsustainable?

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

True or False? Fast reaction rates are desirable in industrial chemical processes.

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

How can the position of equilibrium be changed in reversible reactions?

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

True or False? High percentage yields are undesirable in industrial processes.

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

What is the benefit of selling or reusing waste products?

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

Why do companies continually analyse reactions and processes?

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

What is the relationship between atom economy and raw material usage?

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

How can alternative methods of production improve atom economy?

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

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Yield & Atom Economy (AQA GCSE Chemistry)

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What does percentage yield compare?
Percentage yield compares the actual yield to the theoretical yield.
Define actual yield.
Actual yield is the recorded amount of product obtained from a chemical reaction.
How is the actual yield determined?
The actual yield can be determined by experiment only.
What is theoretical yield?
Theoretical yield is the amount of product that would be obtained under perfect practical and chemical conditions.
What type of calculation lets you determine the theoretical yield?
The type of calculation lets you determine theoretical yield is a reacting mass calculation.
State the equation for percentage yield.
The equation for percentage yield is:
(actual yield $\div$ theoretical yield) x 100
True or False?
A high percentage yield is desirable for economic reasons.
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, what is the percentage yield?
If the actual yield is 1.50 g and theoretical yield is 2.00g, the percentage yield is:
(1.50 $\div$ 2.0) x 100 = 75%
What factors can reduce the percentage yield of a reaction?
Factors that can reduce percentage yield include:
- Incomplete reactions
- Side reactions
- Loss during processing
- Reversible reactions.
What are the steps to calculate theoretical mass of products?
(Higher tier only)
The steps to calculate theoretical mass of products are:
1. Write balanced equation.
2. Convert given mass to moles.
3. Use coefficients to find moles of product.
4. Convert moles of product to mass.
What is the formula to calculate moles from mass?
The formula to calculate moles from mass is:
Moles = mass / molar mass
True or False?
Coefficients in a balanced equation are used to calculate molar masses.
False.
Coefficients in a balanced equation are not used to calculate molar masses. Molar masses are calculated from chemical formulae.
What is the formula to calculate mass from moles?
The formula to calculate mass from moles is:
Mass = moles × molar mass
True or False?
The theoretical yield can only be determined by experiment.
(Higher tier only)
False.
The theoretical yield can be calculated assuming 100% conversion of reactants to products.
How do you determine the molar ratio between reactants and products?
The molar ratio is determined by the coefficients in the balanced chemical equation.
What is the purpose of calculating theoretical masses of products?
(Higher tier only)
Calculating theoretical masses of products allows for comparison with actual yields and determination of percentage yield.
What is atom economy?
Atom economy is a measure of the efficiency of a chemical reaction in terms of how well reactants are utilised to produce useful products.
What information does atom economy give about a reaction?
Atom economy tells us what percentage of the mass of reactants become useful products.
What is the equation that is used to calculate atom economy?
To calculate atom economy:
Atom economy = $\frac{T o t a l M_{r} o f d e s i r e d p r o d u c t}{T o t a l M_{r} o f a l l p r o d u c t s} \times 100$
What is the atom economy of the following reaction?
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
The atom economy for N₂(g) + 3H₂(g) ⇌ 2NH₃(g) is 100% as there is only one product.
True or False?
The higher the atom economy of a process then the more sustainable that process is.
True.
The higher the atom economy of a process then the more sustainable that process is
What is the atom economy for the production of CaO in the following reaction?
CaCO₃→ CaO + CO₂
M_r CaCO₃ = 100, M_r CaO = 56, M_r CO₂ = 44
The atom economy for the production of CaO in the reaction is 56%.
How can the atom economy of a reaction be increased?
The atom economy of a reaction can be increased by selling the by-products of the reaction.
What is the atom economy for the production of ethene?
C₂H₂ + H₂ → C₂H₄
The atom economy for the production of ethene is 100%.
True or False?
Higher atom economy indicates more waste generation.
False.
Higher atom economy means less waste production.
Why is waste reduction in chemical processes important?
Waste reduction in chemical processes is important because it minimises environmental impact and is more sustainable.
How does atom economy relate to waste production?
A lower atom economy indicates more waste production in a reaction.
How can atom economy be improved?
Atom economy can be improved by finding uses for by-products or choosing reaction pathways with fewer unwanted products.
What does an atom economy of 100% indicate?
An atom economy of 100% indicates that all atoms from the reactants end up in the desired product.
List four factors considered when choosing a reaction pathway.
Four factors considered when choosing a reaction pathway are:
- Atom economy
- Percentage yield
- Rates of reaction
- Equilibrium position
Why are reactions with low atom economies unsustainable?
Reactions with low atom economies are unsustainable because they use up too much raw material to manufacture only a small amount of product.
True or False?
Fast reaction rates are desirable in industrial chemical processes.
True.
Fast reaction rates are desirable in industrial chemical processes.
How can the position of equilibrium be changed in reversible reactions?
The position of equilibrium can be changed by altering reaction conditions.
True or False?
High percentage yields are undesirable in industrial processes.
False.
High percentage yields are desirable in industrial chemical processes.
What is the benefit of selling or reusing waste products?
Selling or reusing waste products can improve the atom economy of a reaction.
Why do companies continually analyse reactions and processes?
Companies continually analyse reactions and processes to improve efficiency and reduce costs.
What is the relationship between atom economy and raw material usage?
Higher atom economy means more efficient use of raw materials and less waste production.
How can alternative methods of production improve atom economy?
Alternative methods of production can improve atom economy by producing more useful by-products.

Atomic Structure & the Periodic Table

Bonds, Structure & Properties of Matter

Quantitative Chemistry

Chemical Changes

Energy Changes

Chemical Change: Rate & Extent

Organic Chemistry

Chemical Analysis

Chemistry of the Atmosphere

Using Resources