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Chromatography can be used to test for the purity of substances.
(a) (i) Describe one area in everyday life where purity of substances is important.
.................................................................................................................................................... [1]
(ii) Mineral water contains dissolved salts such as magnesium chloride.
Which one of the following statements about mineral water is correct? Tick one box.
- Mineral water boils at slightly above 100°C. ☐
- Mineral water is pure water. ☐
- Mineral water boils at exactly 100°C. ☐
- Another name for mineral water is fizzy water. ☐ [1]
(b) The diagram shows the apparatus used to separate different dyes in food colourings.
Label the diagram in the boxes provided using the words below.
chromatography paper, origin line, solvent, solvent front [2]
(c) The diagram below shows the chromatography of four different food colourings, A, B, C and D.
(i) Which food colouring, A, B, C or D, contains only one dye? ............................... [1]
(ii) Which three food colourings have one dye in common? ................................. [1]
(iii) Which food colouring contains the greatest number of dyes? ................... [1]
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A student set up an experiment to demonstrate rusting as shown below. He made observations at the start of the experiment, after 2 weeks and after 4 weeks.
(a) What conditions are needed for the iron wool to rust?
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(b) Two weeks after the start of the experiment, the volume of air in the measuring cylinder had decreased. After a further two weeks there was no change in the volume of air. Explain the results of this experiment.
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(c) What change would you observe in the iron wool as it rusted?
appearance at start ......................................................................................................................................
appearance after 2 weeks ........................................................................................................................... [2]
(d) Rust contains iron(III) ions. Describe a test for iron(III) ions.
test .....................................................................................................................................................................
result ................................................................................................................................................................... [2]
(e) Clean iron reacts with dilute hydrochloric acid.
$$ Fe + 2HCl \rightarrow FeCl_2 + H_2 $$
Write a word equation for this reaction.
............................................................................................................................................................................. [2]
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The diagram shows some of the elements in Period 3 of the Periodic Table.
[Table_1: Na, Mg, Si, P, S, Cl, Ar]
(a) From the diagram, choose
(i) one element which forms a basic oxide.
......................................... [1]
(ii) two elements which form acidic oxides.
....................................... and ......................................... [2]
(b) Describe how metallic character of the elements changes across a period.
.................................................................................. [1]
(c) What determines the order of the elements in the Periodic Table?
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(d) The missing element in the table is aluminium.
(i) Describe the structure of an aluminium atom. In your description write about
● the number and types of particles in the nucleus
● the electrons.
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(ii) Use the information in the table below to explain why aluminium is used in preference to iron or titanium for overhead electricity cables. Give two reasons.
[Table_2]
metal | electrical conductivity | density in g/cm3 | melting point /°C | strength | price in £/kg
aluminium | very good | 2.7 | 660 | fairly strong | 24
iron | good | 7.9 | 1535 | strong | 3
titanium | good | 4.5 | 1660 | very strong | 104
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(e) Chlorine is a green gas.
When chlorine is bubbled through an aqueous solution of potassium bromide, the solution turns orange. Complete the symbol equation for this reaction.
$$Cl_2 + \text{.......}KBr \rightarrow \text{...............} + \text{.......}KCl$$ [2]
(f) Argon is a noble gas which is denser than air.
Which one of these statements about argon is correct?
Tick one box.
☐ Argon reacts rapidly with chlorine.
☐ Argon is used for filling balloons.
☐ Argon has a complete outer shell of valency electrons.
☐ Argon has only two valency electrons in its outer shell. [1]
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Ethane is a saturated hydrocarbon. Ethene is an unsaturated hydrocarbon.
(a) Describe how you can distinguish between ethane and ethene using aqueous bromine.
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............................................................................................................................... [2]
(b) The diagram shows the apparatus used to crack long chain alkanes into alkenes and shorter chained alkanes in the laboratory.
(i) State two conditions needed for cracking.
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(ii) What information in the diagram shows that alkenes are insoluble in water?
..................................................................................................................... [1]
(iii) Propene is an alkene.
The formula of propene is $C_3H_6$.
Calculate the relative molecular mass of propene.
(iv) Complete the equation for the cracking of the alkane tetradecane, $C_{14}H_{30}$.
$C_{14}H_{30} \rightarrow$ ............... $+ \ C_{10}H_{22}$ [1]
(c) Poly(ethene) is formed from ethene monomers.
Select two words from the list that describe this reaction.
addition condensation dehydration
fermentation neutralisation polymerisation
...................... and ...................... [2]
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A pupil studied the effect of temperature on the speed of reaction of aqueous sodium thiosulfate with dilute hydrochloric acid.
When he added hydrochloric acid to a solution of sodium thiosulfate, a precipitate of sulfur gradually formed. He recorded the time taken for some writing placed under the flask to disappear from view.
He repeated the experiment at different temperatures. The table shows his results.
[Table_1]
(a) (i) On the grid below, plot a graph of the time taken against temperature. [3]
[Graph_Grid]
(ii) At which temperature was the reaction the fastest? [1]
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(iii) Describe how the temperature affects the speed of reaction. [1]
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(b) Suggest how the speed of this reaction at 30°C will change when the concentration of hydrochloric acid is increased. [1]
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(c) The equation for the reaction is
$ \text{Na}_2\text{S}_2\text{O}_3(\text{aq}) + 2\text{HCl}(\text{aq}) \rightarrow 2\text{NaCl}(\text{aq}) + \text{SO}_2(\text{g}) + \text{S}(\text{s}) + \text{H}_2\text{O}(\text{l}) $
(i) State the name of the salt formed in this reaction. [1]
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(ii) To which group in the Periodic Table does sulfur belong? [1]
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(iii) Sulfur dioxide is formed when coal is burnt in power stations. State one harmful effect of sulfur dioxide on the environment. [1]
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(iv) Sulfur dioxide can be removed in power stations by flue gas desulfurisation. Which one of these compounds is used to remove the sulfur dioxide in this process? Tick one box. [1]
calcium chloride ☐
calcium oxide ☐
nitrogen dioxide ☐
potassium nitrate ☐
(v) Magnesium burns in sulfur dioxide.
$ 2\text{Mg} + \text{SO}_2 \rightarrow 2\text{MgO} + \text{S} $
Refer to this equation to explain why this is a redox reaction. [2]
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(a) In the outer zone of the flame, methane undergoes complete combustion. Complete the equation for the complete combustion of methane.
$CH_4 + ext{..............} \rightarrow CO_2 + 2H_2O$
[2]
(b) In the middle zone of the flame, less air is present and incomplete combustion occurs. State the name of the poisonous gas formed during the incomplete combustion of methane.
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[1]
(c) The inner cone of the flame contains only unburnt methane. A student put a match in the Bunsen burner as shown in the diagram below. He then lit the Bunsen burner.
Suggest why the match did not catch fire.
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[1]
(d) The products of the complete combustion of methane were drawn through the apparatus shown below.
(i) State the name of the substance that turned the white copper sulfate in tube A, blue.
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[1]
(ii) How could you change blue copper sulfate to white copper sulfate?
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[1]
(iii) The soda lime in tube B absorbs carbon dioxide. State and explain what happens to the mass of the soda lime as the experiment proceeds.
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[1]
(e) Methane is a greenhouse gas.
(i) State one source of the methane in the atmosphere.
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[1]
(ii) State one effect of an increased concentration of methane in the atmosphere.
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[1]
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A student studied the reaction of citric acid with sodium hydrogen carbonate. She put a solution of citric acid in a plastic cup and measured its temperature. She then added sodium hydrogen carbonate powder and measured the temperature again.
- Diagram showing the setup with 'lid', 'sodium hydrogen carbonate', 'thermometer', 'plastic cup', 'citric acid solution'.
(a) The temperature of the reaction mixture decreased. Which one of these statements about this reaction is correct? Tick one box.
The reaction released heat energy. []
The reaction is exothermic. []
The reaction is endothermic. []
The products have less energy than the reactants. []
[1]
(b) The structure of citric acid is shown below.
COOH
|
CH2
|
HO—C—COOH
|
CH2
|
COOH
(i) On this structure, put a ring around the alcohol functional group. [1]
(ii) Write the simplest formula for citric acid.
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(c) Salts of citric acid can be prepared from lemon juice.
(i) The lemon juice is first boiled to remove various substances including enzymes. What do you understand by the term *enzyme*?
...........................................................................................................................[2]
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(ii) The lemon juice is then neutralised with calcium carbonate and solid calcium citrate is formed. Suggest how the calcium citrate can be separated from the mixture.
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(iii) Carbon dioxide gas is released when citric acid solution reacts with calcium carbonate. Describe a test for carbon dioxide.
test ..............................................................................................................................................................
result ............................................................................................................................................................ [2]
(d) The concentration of a citric acid solution can be found by carrying out a titration using the apparatus shown below.
- Diagram showing 'sodium hydroxide solution', 'citric acid solution'.
Describe how to carry out this titration.
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The diagram shows an electrolysis cell for extracting sodium from molten sodium chloride.
(a) (i) Which letter on the diagram represents
the electrolyte? ...................................................................................................................
the cathode? ..................................................................................................................... [2]
(ii) Which one of the following substances is most likely to be used as the anode? Put a ring around the correct answer.
graphite sodium sulfur zinc [1]
(b) What information from the diagram suggests that sodium is less dense than molten sodium chloride?
.............................................................................................................................................. [1]
(c) Predict the product formed at the anode during this electrolysis.
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(d) Name the gases formed at the anode and cathode when an aqueous solution of sodium chloride is electrolysed.
product at the anode .........................................................................................................
product at the cathode ...................................................................................................... [2]
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