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The structures of some substances containing carbon are shown:
Answer the following questions about these substances.
(a) (i) Which two substances have giant covalent structures?
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(ii) Which substance decolourises aqueous bromine?
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(iii) Which substance is most likely to be a gas at room temperature and pressure?
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(iv) Which substance is a hydrocarbon?
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(v) Determine the simplest formula for substance D.
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(b) Two isotopes of carbon are $^{13}_{6}C$ and $^{14}_{6}C$.
(i) How do these two isotopes differ in their atomic structure?
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(ii) Determine the number of neutrons present in one atom of the isotope $^{14}_{6}C$.
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This question is about metals.
(a) The table shows some properties of the metals, R, S, T and U.
[Table_1]
| metal | relative electrical conductivity | relative heat conductivity | density in $\text{g/cm}^3$ | melting point /$^\circ$C |
|-------|-----------------------------------|-----------------------------|-----------------------------|---------------------------|
| R | 4.3 | 11.8 | 2.7 | 660 |
| S | 1.2 | 4.2 | 7.9 | 1535 |
| T | 6.2 | 22.3 | 8.9 | 1083 |
| U | 4.1 | 12.4 | 7.1 | 420 |
Which metal would be best to make the base of a pan for cooking food?
Use the information in the table to explain your answer.
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(b) Zinc chloride can be made by reacting excess zinc with hydrochloric acid.
Suggest how the excess zinc can be removed from the reaction mixture.
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(c) Zinc can be obtained from molten zinc chloride by electrolysis.
(i) What is meant by the term \textit{electrolysis}?
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(ii) Draw a labelled diagram of the apparatus that could be used to electrolyse molten zinc chloride.
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(d) Give \textit{one} advantage of recycling metals.
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The table gives some information about the halogens.
| element | colour | melting point / ℃ | boiling point / ℃ |
|---|---|---|---|
| chlorine | light green | −101 | −35 |
| bromine | red‑brown | −7 | +59 |
| iodine | grey‑black | +114 | +184 |
| astatine | +302 | +337 |
(a)
(i) Predict the colour of astatine.
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(ii) Describe the trend in the boiling points of the halogens.
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(iii) Deduce the state of chlorine at −50℃. Explain your answer.
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(b)
(i) Complete the word equation for the reaction of bromine with aqueous potassium astatide.
bromine + potassium astatide → ..................................... + ...................................... [2]
(ii) Suggest why bromine does not react with aqueous potassium chloride.
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(c) Compound X is used to prepare the dye methyl orange. The structure of compound X is shown.
Complete the table and calculate the relative molecular mass of compound X.
| type of atom | number of atoms | atomic mass | |
|---|---|---|---|
| carbon | 6 | 12 | 6 × 12 = 72 |
| hydrogen | 5 | 1 | 5 × 1 = 5 |
| nitrogen | 2 | 14 | 2 × 14 = 28 |
| sulfur | 1 | 32 | 1 × 32 = 32 |
| oxygen | |||
| chlorine |
relative molecular mass = .......................... [2]
(d) Describe how you could use methyl orange to distinguish between solutions of hydrochloric acid and sodium hydroxide.
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(e) Methyl orange and Congo red are dyes. A mixture of methyl orange and Congo red can be separated by chromatography.
Draw a labelled diagram to show how the apparatus is arranged to carry out chromatography. [3]
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(a) What is the meaning of the term hydrocarbon?
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(b) Petroleum can be separated into different fractions by fractional distillation.
The diagram shows a fractionating column. The fractions are shown by letters.
Describe how fractional distillation is used to separate the petroleum into fractions.
In your answer refer to
• changes of state,
• differences in boiling points.
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(c) The properties of the fractions are shown in the table.
[Table_1]
(i) Describe how the number of carbon atoms affects the boiling range.
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(ii) Determine the percentage by mass of fraction F in this sample of petroleum.
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(iii) Which one of the fractions is mainly gaseous at 25°C?
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(iv) Fraction F is the residue. It contains bitumen. Give one use of bitumen.
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(d) Fraction C can be cracked to form alkenes.
(i) Describe one condition required for cracking.
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(ii) Complete the chemical equation for the cracking of dodecane, $$C_{12}H_{26}$$, to form heptane, $$C_{7}H_{16}$$, and one other hydrocarbon.
$$C_{12}H_{26} \rightarrow C_{7}H_{16} + ............$$ [1]
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Iron is a transition element.
(a) Describe the physical and chemical properties of iron.
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(b) Iron carbonyl, Fe(CO)$_{5}$, is a covalent liquid.
(i) Suggest two physical properties of iron carbonyl.
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(ii) When heated above 200 °C, iron carbonyl undergoes thermal decomposition.
$$ ext{Fe(CO)}_5(l)
ightarrow ext{Fe}(s) + 5 ext{CO}(g) $$
Explain why this reaction could have an adverse effect on health if not carried out in a fume cupboard.
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Ethanol can be manufactured by reacting ethene with steam.
$$
\text{C}_2\text{H}_4(g) + \text{H}_2\text{O}(g) \rightleftharpoons \text{C}_2\text{H}_5\text{OH}(g)
$$
(a) What is the meaning of the symbol $\rightleftharpoons$?
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(b) State two conditions needed for this reaction.
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(c) The energy level diagram for this reaction is shown.
Is this reaction exothermic or endothermic?
Give a reason for your answer.
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(d) The graph below shows how the percentage yield of ethanol changes with temperature when the pressure is kept constant.
(i) Describe how the percentage yield changes with temperature.
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(ii) Determine the percentage yield when the temperature is 350 °C.
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(e)(i) Complete the structure of ethanol, $\text{C}_2\text{H}_5\text{OH}$, to show all atoms and all bonds.
[1]
(ii) Give one use of ethanol.
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(iii) Complete the chemical equation for the complete combustion of ethanol.
$$
\text{C}_2\text{H}_5\text{OH} + 3\text{O}_2 \rightarrow ....\text{CO}_2 + ....\text{H}_2\text{O}
$$ [2]
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A student investigated the reaction between zinc and sulfuric acid at 20 °C using the apparatus shown. The zinc was in excess.
(a) What should the student do to start the reaction?
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(b) The graph shows the volume of hydrogen released as the reaction proceeds.
(i) Explain why the volume of gas stays the same after 10 minutes.
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(ii) How long did it take for the first 20 cm^3 of gas to be collected?
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(iii) The student repeated the experiment at 30 °C. All other conditions remained the same. Draw the shape of the line on the grid on page 16 when the reaction was carried out at 30 °C.
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(c) The student repeated the experiment using zinc powder instead of small pieces of zinc. Describe and explain how the rate of reaction differs when zinc powder is used.
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(d) Sulfuric acid is a compound.
(i) What is the meaning of the term compound?
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(ii) Sulfur is used to make sulfuric acid. Give one source of sulfur.
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(iii) Sulfur is oxidised by air to form sulfur dioxide. Give one use of sulfur dioxide.
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The graph shows how increasing the pressure at constant temperature changes the volume of a fixed mass of carbon dioxide gas.
(a) Describe how the volume of gas changes with pressure.
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(b) What happens to the average distance of the molecules from each other when the pressure is decreased?
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(c) Carbon dioxide can be reduced by magnesium.
$$2Mg(s) + CO_2(g) \rightarrow 2MgO(s) + C(s)$$
(i) Use the information in the equation to show that carbon dioxide gets reduced.
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(ii) Which one of these processes does not produce carbon dioxide?
Tick one box.
respiration □
reaction of an acid with a metal oxide □
reaction of an acid with a carbonate □
thermal decomposition of limestone □ [1]
(iii) Give two problems caused by increasing the amount of carbon dioxide in the atmosphere.
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