Q1.
Toothpastes often contain fluoride ions to help protect teeth from attack by bacteria.
Some toothpastes contain tin(II) fluoride.
This compound has the formula SnF2 .
(a)
Calculate the relative formula mass (M r) of SnF2.
Relative atomic masses: F = 19; Sn = 119
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Relative formula mass (M r) = ..........................................
(2)
(b)
Calculate the percentage by mass of fluorine in SnF2.
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Percentage by mass of fluorine = .......................................... %
(2)
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(c)
A tube of toothpaste contains 1.2 g of SnF2.
Calculate the mass of fluorine in this tube of toothpaste.
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Mass of fluorine = .......................................... g
(1)
(d)
The diagram represents the electron arrangement of a fluorine atom.
Explain how a fluorine atom can change into a fluoride ion, F–.
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(2)
(Total 7 marks)
Q2.
Aspirin tablets have important medical uses.
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(a)
Aspirin is made when salicylic acid reacts with ethanoic anhydride.
The equation for this reaction is:
C7H6O3
salicylic acid
+
C4H6O3
→
C9H8O4
+
CH3COOH
aspirin
Calculate the maximum mass of aspirin that could be made from 100 g of salicylic acid.
Show clearly how you work out your answer.
The relative formula mass (M r) of salicylic acid (C7H6O3) is 138.
The relative formula mass (M r) of aspirin (C9H8O4) is 180.
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Maximum mass of aspirin = .................................... g
(2)
(b)
(i)
In an experiment a chemist calculated that the maximum yield of aspirin is 400 g.
The chemist did the experiment but only made 250 g of aspirin.
Calculate the percentage yield of aspirin for this experiment.
Show clearly how you work out your answer.
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Percentage yield of aspirin = ........................... %
(2)
(ii)
Suggest one possible reason why the chemist did not have a percentage
yield of 100%.
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(1)
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(c)
The use of a catalyst might reduce costs in the industrial production of aspirin.
Suggest how.
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(1)
(Total 6 marks)
Q3.
Petrol is a mixture of hydrocarbons such as octane, C8H18
When petrol is burned in a car engine, a large amount of carbon dioxide is produced.
This car uses 114 g of petrol to travel one mile.
Calculate the mass of carbon dioxide produced when this car travels one mile.
Assume that petrol is octane and that combustion is complete.
(Relative atomic masses: H = 1; C = 12; O = 16)
The combustion of octane can be represented by this equation.
C8H18 + 12
O2 → 8CO2 + 9H2O
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Mass of carbon dioxide = ........................ g
(Total 3 marks)
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Q4.
This drinks bottle is made of thermosoftening plastic.
Drinks bottles of this type can be recycled.
Describe and explain how the bottles can be changed into new plastic objects.
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(Total 4 marks)
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