Cons. of Mass, Chemical Measurements - Eqns 2 QP
Cons. of Mass, Chemical Measurements - Eqns 2 QP
Cons. of Mass, Chemical Measurements - Eqns 2 QP
The water and carbon dioxide produced escape from the test tube.
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(1)
(b) (i) Calculate the relative formula mass (Mr) of copper oxide (CuO).
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(iii) Calculate the maximum mass of copper that could be produced from 4.0 g of copper
oxide.
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The mass of copper oxide used and the mass of copper produced were measured each
time.
Experiment
1 2 3
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(ii) Suggest how the results of the experiment could be made more precise.
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(1)
(iii) The three experiments gave different results for the amount of copper produced.
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(2)
(Total 10 marks)
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Q2.Figure 1 shows the outer electrons in an atom of the Group 1 element potassium and in an atom of
the Group 6 element sulfur.
Figure 1
Describe what happens when two atoms of potassium react with one atom of sulfur.
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(b) The structure of potassium sulfide can be represented using the ball and stick model in
Figure 2.
Figure 2
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The ball and stick model is not a true representation of the structure of potassium sulfide.
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(1)
Complete the dot and cross diagram to show the covalent bonding in a molecule of
hydrogen sulfide.
(2)
(d) Calculate the relative formula mass (Mr) of aluminium sulfate Al2(SO4)3
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(e) Covalent compounds such as hydrogen sulfide have low melting points and do not conduct
electricity when molten.
Draw one line from each property to the explanation of the property.
Explanation
Property
of property
Weak intermolecular
forces of attraction
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(2)
(f) Ionic compounds such as potassium sulfide have high boiling points and conduct electricity
when dissolved in water.
Draw one line from each property to the explanation of the property.
Explanation
Property
of property
Weak intermolecular
forces of attraction
Conduct electricity
when molten
(2)
(Total 14 marks)
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Q3. Some students investigated magnesium oxide.
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(b) The students calculated that if they used 0.12 g of magnesium they should make 0.20 g of
magnesium oxide.
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• The students weighed 0.12 g of magnesium ribbon into a crucible.
• They lifted the lid of the crucible slightly from time to time to allow air into the
crucible.
• The students tried to avoid lifting the lid too much in case some of the magnesium
oxide escaped.
• When all of the magnesium appeared to have reacted, the students weighed the
magnesium oxide produced.
(i) The mass of magnesium oxide produced was lower than the students had calculated.
They thought that this was caused by experimental error.
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(2)
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(ii) The students only did the experiment once.
Give two reasons why they should have repeated the experiment.
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(2)
(Total 9 marks)
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Q4. Some students did an experiment to find the relative formula mass (Mr) of a gas.
• The mass of the canister of gas was measured using a balance, which weighed to two
decimal places.
• The measuring cylinder was filled with 1 dm3 of the gas from the canister.
(a) The results for one of the experiments are shown in the table below.
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Mass = ................................................................. g
(1)
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(b) How could the results be made more precise?
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(1)
(c) The students used their results to calculate values for the relative formula mass (Mr) of this
gas.
The results are shown in the table below.
Experiment 1 2 3 4
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Mean = ...................................................................
(2)
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(2)
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(1)
(d) The teacher told the students that the formula of the gas is C3H8
Calculate the relative formula mass (Mr) of this gas. You should show your working.
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Q5. An experiment was done on the reaction of copper oxide (CuO) with methane (CH4).
The water and carbon dioxide produced escapes from the test tube.
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(1)
(b) (i) Calculate the relative formula mass (Mr) of copper oxide (CuO).
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(2)
(iii) Calculate the mass of copper that could be made from 4.0 g of copper oxide.
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Experiment
1 2 3
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(ii) Suggest how the results of these experiments could be made more precise.
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(1)
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(iii) The three experiments gave slightly different results for the mass of copper made.
This was caused by experimental error.
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(2)
(Total 10 marks)
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Q6. (a) The table gives information about two isotopes of hydrogen, hydrogen-1 and
hydrogen-2.
Hydrogen-1 Hydrogen-2
Atomic number 1 1
Mass number 1 2
(1)
(b) (i) Calculate the relative formula mass (Mr) of water, H2O
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(2)
(c) Molecules of heavy water contain two atoms of hydrogen-2 instead of two atoms of
hydrogen-1.
Explain why a molecule of heavy water has more mass than a normal water molecule.
You should refer to the particles in the nucleus of the two different hydrogen atoms in your
answer.
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(2)
(Total 6 marks)
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