The yield of a chemical reaction describes how much product is actually made.
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What is the percentage yield of a chemical reaction?
The percentage yield of a chemical reaction tells us how much product is made compared with the maximum amount that could be made.
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Why is it important to maximise yield and minimise energy wasted?
To conserve the Earth's limited resources and reduce pollution and make production more sustainable.
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What equation is used to calculate percentage yield?
Percentage yield = (amount of product collected ÷ maximum amount of product possible) x 100%.
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How do we know what the maximum amount of product possible is?
The maximum amount of product possible is calculated from the balanced equation for the reaction.
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What is the percentage yield if a student collected 2.3g of magnesium oxide from 2.0g of magnesium?
Theoretically: 2Mg+O_2→2MgO, so 48g of Mg should gibe 80g of MgO and so 2.0g of Mg should give 2x80÷48=3.33g of MgO. Therefore percentage yield is (2.3÷3.33)x100=69%.
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Why is it not usually possible to collect the amounts calculated from the chemical equations when you actually do chemical reactions?
Reactions may not go to completion, other reactions may happen and some product may be lost when it is separated or collected from the apparatus.
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A student made 4.4g of calcium oxide from 4.0g of calcium, what is the percentage yield?
Why is it not usually possible to get 100% yield from a chemical reaction?
Reactions may not go to completion, other reactions may happen, some product may be lost when separated or collected.
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Why should chemical manufacturers use reactions with high yields?
To help conserve resources, reduct waste and/or pollution.
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**YOU NEED TO BE ABLE TO CALCULATE PERCENTAGE YIELDS FOR HIGHER FROM INFORMATION ABOUT THE MASS OF PRODUCT OBTAINED AND THE EQUATION FOR THE REACTION**
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Other cards in this set
Card 2
Front
What is the percentage yield of a chemical reaction?
Back
The percentage yield of a chemical reaction tells us how much product is made compared with the maximum amount that could be made.
Card 3
Front
Why is it important to maximise yield and minimise energy wasted?
Back
Card 4
Front
What equation is used to calculate percentage yield?
Back
Card 5
Front
How do we know what the maximum amount of product possible is?
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