Download AS Paper 1 Practice Paper 16 - A

Paddington Academy
AS LEVEL CHEMISTRY
PAPER 1
PRACTICE PAPER 16
(structured questions only)
Answer all questions
Max 80 marks
Name
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Mark
……../80
……....%
Grade ………
Note – this paper only contains structured questions
Page 1
Paddington Academy
1.
When a sample of liquid, X, of mass 0.406 g was vaporised, the vapour was found to occupy a
volume of 2.34 × 10–4 m3 at a pressure of 110 kPa and a temperature of 473 K.
(a)
Give the name of the equation pV = nRT.
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(1)
(b)
Use the equation pV = nRT to calculate the number of moles of X in the sample and
hence deduce the relative molecular mass of X.
(The gas constant R = 8.31 J K–1 mol–1)
Moles of X ....................................................................................................
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Relative molecular mass of X .......................................................................
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(4)
(c)
Compound X, which contains carbon, hydrogen and oxygen only, has 38.7% carbon and
9.68% hydrogen by mass. Calculate the empirical formula of X.
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(3)
(d)
Using your answers to parts (b) and (c) above, deduce the molecular formula of X.
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(1)
(Total 9 marks)
Page 2
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2.
(a)
The equation for the reaction between magnesium carbonate and hydrochloric acid is
given below.
MgCO3 + 2HCl → MgCl2 + H2O + CO2
When 75.0 cm3 of 0.500 mol dm–3 hydrochloric acid were added to 1.25 g of impure
MgCO3 some acid was left unreacted. This unreacted acid required 21.6 cm3 of a
0.500 mol dm–3 solution of sodium hydroxide for complete reaction.
(i)
Calculate the number of moles of HCl in 75.0 cm3 of 0.500 mol dm–3 hydrochloric
acid.
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(ii)
Calculate the number of moles of NaOH used to neutralise the unreacted HCl.
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(iii)
Show that the number of moles of HCl which reacted with the MgCO3 in the sample
was 0.0267
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(iv)
Calculate the number of moles and the mass of MgCO3 in the sample, and hence
deduce the percentage by mass of MgCO3 in the sample.
Moles of MgCO3 ..................................................................................
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Mass of MgCO3 ...................................................................................
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Percentage of MgCO3 ..........................................................................
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(8)
Page 3
Paddington Academy
(b)
A compound contains 36.5% of sodium and 25.5% of sulphur by mass, the rest being
oxygen.
(i)
Use this information to show that the empirical formula of the compound is Na2SO3
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(ii)
When Na2SO3 is treated with an excess of hydrochloric acid, aqueous sodium
chloride is formed and sulphur dioxide gas is evolved. Write an equation to
represent this reaction.
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(4)
(Total 12 marks)
Page 4
Paddington Academy
3.
Some airbags in cars contain sodium azide (NaN3).
(a)
Sodium azide has a high melting point.
Predict the type of bonding in a crystal of sodium azide.
Suggest why its melting point is high.
Type of bonding .............................................................................................
Reason for high melting point ........................................................................
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(3)
(b)
The azide ion has the formula N3−
(i)
The azide ion can be represented as N
N − N−
One of these bonds is a co−ordinate bond.
On the following diagram, draw an arrowhead on one of the bonds to represent the
direction of donation of the lone pair in the co−ordinate bond.
N
N − N−
(1)
(ii)
Give the formula of a molecule that has the same number of electrons as the azide
ion.
...............................................................................................................
(1)
(iii)
Which is the correct formula of magnesium azide?
Tick (✓) one box.
Mg3N
MgN
MgN6
Mg3N2
(1)
(Total 6 marks)
Page 5
Paddington Academy
4.
A hydrogen peroxide molecule can be represented by the structure shown.
(a)
Suggest a value for the H−O−O bond angle.
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(1)
(b)
Hydrogen peroxide dissolves in water.
(i)
State the strongest type of interaction that occurs between molecules of hydrogen
peroxide and water.
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(1)
(ii)
Draw a diagram to show how one molecule of hydrogen peroxide interacts with one
molecule of water.
Include all lone pairs and partial charges in your diagram.
(3)
(c)
Explain, in terms of electronegativity, why the boiling point of H2S2 is lower than H2O2.
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(2)
(Total 7 marks)
Page 6
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5.
(a)
Explain why certain elements in the Periodic Table are classified as p-block elements.
Illustrate your answer with an example of a p-block element and give its electronic
configuration.
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(3)
(b)
Explain the meaning of the term periodicity as applied to the properties of rows of
elements in the Periodic Table. Describe and explain the trends in atomic radius, in
electronegativity and in conductivity for the elements sodium to argon.
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(13)
(Total 16 marks)
Page 7
Paddington Academy
6.
This question is about the extraction of metals.
(a)
Manganese can be extracted from Mn2O3 by reduction with carbon monoxide at high
temperature.
(i)
Use the standard enthalpy of formation data from the table and the equation for the
extraction of manganese to calculate a value for the standard enthalpy change of
this extraction.
Mn2O3(s)
CO(g)
Mn(s)
CO2(g)
−971
−111
0
−394
ΔHfϴ/ kJ mol−1
Mn2O3(s) + 3CO(g)
2Mn(s) + 3CO2(g)
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(3)
(ii)
State why the value for the standard enthalpy of formation of Mn(s) is zero.
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(1)
(b)
Titanium is extracted in industry from titanium(IV) oxide in a two-stage process.
Write an equation for the second stage of this extraction in which titanium(IV) chloride is
converted into titanium.
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(2)
(c)
Chromium is extracted in industry from chromite (FeCr2O4).
(i)
In the first stage of this extraction, the FeCr2O4 is converted into Na2CrO4 Balance
the equation for this reaction.
.........FeCr2O4 + .........Na2CO 3 + .........O 2
.........Na2CrO4 + 2Fe2O 3 + 8CO2
(1)
(ii)
In the final stage, chromium is extracted from Cr2O3 by reduction with aluminium.
Write an equation for this reaction.
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(1)
(Total 8 marks)
Page 8
Paddington Academy
7.
Ammonia is used to make nitric acid (HNO3) by the Ostwald Process.
Three reactions occur in this process.
Reaction 1 4NH3(g) + 5O2(g)
Reaction 22NO(g) + O2(g)
2NO2(g)
Reaction 3 3NO2(g) + H2O(I)
(a)
4NO(g) + 6H2O(g)
2HNO3(aq) + NO(g)
Suggest why a leak of NO2 gas from the Ostwald Process will cause atmospheric
pollution.
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(1)
(b)
Give one reason why excess air is used in the Ostwald Process.
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(1)
(c)
Ammonia reacts with nitric acid as shown in this equation.
NH3 + HNO3
NH4NO3
Deduce the type of reaction occurring.
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(1)
(Total 3 marks)
8.
Iodine reacts with concentrated nitric acid to produce nitrogen dioxide (NO2).
(a)
(i)
Give the oxidation state of iodine in each of the following.
I2 .......................................................................
HIO3..................................................................
(2)
(ii)
Complete the balancing of the following equation.
l2
+
10HNO3
..........HIO3
+
..........NO2
+
..........H2O
(1)
Page 9
Paddington Academy
(b)
In industry, iodine is produced from the NalO3 that remains after sodium nitrate has been
crystallised from the mineral Chile saltpetre.
The final stage involves the reaction between NalO3 and Nal in acidic solution.
Half-equations for the redox processes are given below.
IO3–
+
5e–
+
6H+
l-
3H2O
1/2I2
+
+
1/2I2
e–
Use these half-equations to deduce an overall ionic equation for the production of iodine
by this process. Identify the oxidising agent.
Overall ionic equation
The oxidising agent .......................................................................................
(2)
(c)
When concentrated sulfuric acid is added to potassium iodide, solid sulfur and a black
solid are formed.
(i)
Identify the black solid.
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(1)
(ii)
Deduce the half-equation for the formation of sulfur from concentrated sulfuric acid.
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(1)
(d)
When iodide ions react with concentrated sulfuric acid in a different redox reaction, the
oxidation state of sulfur changes from +6 to -2. The reduction product of this reaction is a
poisonous gas that has an unpleasant smell.
Identify this gas.
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(1)
Page 10
Paddington Academy
(e)
A yellow precipitate is formed when silver nitrate solution, acidified with dilute nitric acid,
is added to an aqueous solution containing iodide ions.
(ii)
Write the simplest ionic equation for the formation of the yellow precipitate.
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(1)
(ii)
State what is observed when concentrated ammonia solution is added to this
precipitate.
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(1)
(iii)
State why the silver nitrate is acidified when testing for iodide ions.
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(1)
(f)
Consider the following reaction in which iodide ions behave as reducing agents.
Cl2(aq) + 2I–(aq)
(i)
I2(aq)
+ 2Cl–(aq)
In terms of electrons, state the meaning of the term reducing agent.
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(1)
(ii)
Write a half-equation for the conversion of chlorine into chloride ions.
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(1)
(iii)
Suggest why iodide ions are stronger reducing agents than chloride ions.
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(2)
(Total 15 marks)
Page 11
Paddington Academy
9.
Sodium phosphate and ammonia are formed when ammonium phosphate is heated with
sodium hydroxide solution in a conical flask. There is one other product in this reaction.
(a)
Complete and balance the equation for the reaction of ammonium phosphate with sodium
hydroxide.
(NH4)3PO4
+
...... NaOH
Na3PO4
+
...... NH3
+
............
(2)
(b)
Ammonia is an alkaline gas. Describe how you would use a named indicator to show that
ammonia gas is released from the flask in this reaction. State the colour change that you
would observe.
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(2)
(Total 4 marks)
Page 12