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Sucrose is a carbohydrate - Edexcel - GCSE Chemistry - Question 4 - 2022 - Paper 1
Question 4
Sucrose is a carbohydrate. When a solution of sucrose is fermented using yeast, ethanol is formed. sucrose + water ⇌ ethanol + carbon dioxide In one experiment, 1... show full transcript
Worked Solution & Example Answer:Sucrose is a carbohydrate - Edexcel - GCSE Chemistry - Question 4 - 2022 - Paper 1
Step 1
State the meanings of the terms actual yield and theoretical yield.
Answer
The actual yield refers to the mass (amount/yield) of product formed in the reaction or experiment. In contrast, the theoretical yield is the maximum amount of product that could be formed from the complete conversion of the limiting reactant under ideal conditions, assuming no losses.
Step 2
Step 3
State two reasons why the actual yield of a reaction is usually less than the theoretical yield.
Answer
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Some reactant may remain unreacted, meaning that not all of the starting materials are converted into products.
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Side reactions could occur, leading to the formation of by-products instead of the desired product.
Step 4
Calculate the atom economy of this reaction to produce ethanol.
Answer
To calculate the atom economy, we use:
Here, the desired product is ethanol. The molar masses are:
- Ethanol (C2H5OH) = 46 g/mol
- Total mass of products = mass of 4 moles of ethanol + mass of 4 moles of CO2.
- Molar mass of CO2 = 44 g/mol,
So Total mass of products = 4(46) + 4(44) = 184 + 176 = 360 g.
Thus, Atom economy =
Rounding to two significant figures gives:
Step 5
Explain the effect on the atom economy of this reaction if the carbon dioxide produced was to make fizzy drinks.
Answer
If the carbon dioxide produced is utilized for making fizzy drinks, it effectively becomes a part of the desired end product. This utilization increases the total mass of useful products, thereby increasing the atom economy of the reaction, as less mass is wasted in the form of by-products.