Question
Zinc is extracted from an ore containing zinc sulfide.
(a) State the name of this zinc ore…………………………………………………………………………………………………………………………….. [1]
(b) This ore is converted to zinc oxide, ZnO.
Zinc oxide is then reacted with carbon.
(i) Write a chemical equation for the reaction of zinc oxide with carbon………………………………………………………………………………………………………………………. [1]
(ii) State what type of chemical change happens to the zinc in zinc oxide in this reaction.
Explain your answer.
chemical change …………………………………………………………………………………………………..
explanation ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………….[2]
(iii) Explain why aluminium is not extracted from aluminium oxide by heating with carbon………………………………………………………………………………………………………………………. [1]
(iv) Suggest an alternative method for the extraction of zinc from zinc oxide……………………………………………………………………………………………………………………… [1]
(c) Brass is an alloy of zinc.
Explain, in terms of particles, why brass is harder than pure zinc…………………………………………………………………………………………………………………………….. [3]
▶️Answer/Explanation
Ans:
2(a) zinc blende
2(b)(i) $\begin{aligned} & \mathrm{ZnO}+\mathrm{C} \rightarrow \mathrm{Zn}+\mathrm{CO} \\ & \text { or } \\ & 2 \mathrm{ZnO}+\mathrm{C} \rightarrow 2 \mathrm{Zn}+\mathrm{CO}_2\end{aligned}$
2(b)(ii) chemical change: reduction (1)
explanation: oxygen is lost (1)
2(b)(iii) aluminium is more reactive than carbon
2(b)(iv) electrolysis
2(c) exists as layers (1)
(alloy) contains different sized (copper) atoms (1)
makes it more difficult for layers (of atoms) to slide over each slip/shift other (1)
Question
Zinc and copper are elements next to each other in the Periodic Table.
(a) Zinc is obtained from zinc blende in a two-step process.
● In step 1, zinc blende is converted into zinc oxide.
● In step 2, zinc oxide is converted into zinc in a blast furnace.
Outline how each of these steps are done.
In your answer:
● give one chemical equation for each step
● describe how zinc is removed from the blast furnace in step 2.
step 1 ……………………………………………………………………………………………………………………….
chemical equation ……………………………………………………………………………………………………….
step 2 ……………………………………………………………………………………………………………………….
chemical equation ……………………………………………………………………………………………………….
removal of zinc in step 2 ……………………………………………………………………………………………..
(b) Name the alloy formed when zinc is mixed with copper.
…………………………………………………………………………………………………………………………….
(c) Copper is a transition element. It can have variable oxidation states.
State two other chemical properties of transition elements which make them different from
Group I elements.
1 ……………………………………………………………………………………………………………………………….
2 ……………………………………………………………………………………………………………………………….
(d) A compound of copper can be used to test for water.
(i) State the full name of this compound of copper.
………………………………………………………………………………………………………………………
(ii) State the colour change that occurs when water is added to this compound of copper.
from …………………………………………………….. to ……………………………………………………….
(e) Aqueous potassium iodide reacts with aqueous copper(II) sulfate to produce iodine.
(i) Balance the chemical equation for this reaction.
(ii) Deduce the charge on the copper ion in CuI.
………………………………………………………………………………………………………………………
(iii) In terms of electron transfer, explain why copper is reduced in this reaction.
………………………………………………………………………………………………………………………
(iv) Identify the reducing agent.
………………………………………………………………………………………………………………………
Answer/Explanation
Ans:
3. (a) roast zinc blende (in air)
2ZnS + \(3O_{2}\) → 2ZnO + \(2SO_{2}\)
add/react with coke
ZnO + C → Zn + CO OR 2ZnO + C → 2Zn + \(CO_{2}\)
(zinc is) distilled
(b) brass
(c) form coloured compounds / ions
act as catalysts
(d) (i) anhydrous copper(II) sulfate
(ii) white
blue
(e) (i) \(4KI+2CuSO_{4}\rightarrow 2CuI+I_{2}+2K_{2}SO_{4}\)
(ii) 1+
(iii) gains electron(s)
(iv) KI / potassium iodide / iodide (ions) / I–
Question
A student used chromatography to separate the dyes in the blue ink from a ball-point pen. She used the equipment shown in the diagrams below.
(a) Complete the diagram below to show how she set up the apparatus.[3]
(b) Describe how chromatography could be used by the student to separate the dyes.[3]
(c) The student used water as a solvent. Suggest a different solvent that she could use.[1]
(d) The diagram below shows the results of the chromatography using the blue ink, B, and several pure dyes, W, X, Y and Z.
(i) Which of the dyes, W, X, Y and Z, were in the blue ink?[1]
(ii) How many dyes in the ink had been separated by this chromatography?[1]
(e) The diagram shows the ball-point pen used in the experiment.
(i) The cap of the pen is made of poly(ethene).
Describe the formation of poly(ethene) from ethene. In your answer, include the words:[2]
-
-
- monomer,
- polymer.
-
(ii) The tip of the pen is made from an alloy.
What is meant by the term alloy ?[1]
(f) The table shows some properties of four alloys.
(i) How does the strength of the steel and aluminum alloys vary with their thermal conductivity?[1]
(ii) Which one of these alloys is the best one to use to make the body of an aircraft? Give two reasons for your answer.[3] [Total: 16]
Answer/Explanation
Ans:
7 (a) square / rectangular sheet of paper in chromatography tank;
note: the sheet should not touch the sides of the beaker
solvent at bottom of tank with paper dipping into it;
note: solvent does not have to be labelled / paper can just touch the surface
But there should be no gap between the solvent and the paper
watch glass over the tank (this can just be shown as a line);
(b) place spot of ink / dye on the paper;
note: answer must imply a spot or drop (not just ink put on paper)
above the solvent level;
let the solvent run up the paper / solvent moves the dyes up the paper / some idea that solvent is needed for the movement of the spots;
(c) any suitable solvent e.g. ethanol / butanol / ester / alcohol
(d) (i) W, X and Y;
(ii) 4 / four;
(e) (i) idea that ethene is the monomer / idea that monomers are the simple (or basic) units which add together;
idea that poly(ethene) is the polymer / idea that the polymer is formed by adding ethene units / simple units combine to form polymer / idea that polymer is a very long (hydrocarbon) chain;
note: (ethene) monomers join to make a polymer = 2 marks
(ii) mixture of metals / mixture of metal + non metal;
(f) (i) increasing strength decreases (thermal) conductivity / the lower the conductivity the higher the strength;
(ii) high strength aluminum;
has high strength / it is strong / aircraft body need to be strong;
it has low density / it is light(weight) / aircraft body needs to be light(weight)