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
Period 3 contains the elements sodium to argon. This question asks about the chemistry of each of the Period 3 elements or their compounds.
(a) Sodium nitrate is a white crystalline solid. When heated it melts and the following reaction occurs.
\(2NaNO_3(l) → 2NaNO_2(l) + O_2\)(g)
A 3.40g sample of sodium nitrate is heated. Calculate the
• number of moles of \(NaNO_3\) used, ……………………………. mol
• number of moles of \(O_2\) formed, ……………………………. mol
• volume of \(O_2\) formed, in \(dm^{3}\) (measured at r.t.p.). …………………………….\( dm^{3}\)
[3]
(b) Magnesium reacts slowly with warm water to form a base, magnesium hydroxide.
(i) Explain what is meant by the term base.
……………………………………………………………………………………………………………………… [1]
(ii) Write a chemical equation for the reaction between magnesium and warm water.
……………………………………………………………………………………………………………………… [2]
(c) Aluminium oxide is amphoteric. It is insoluble in water. Describe experiments to show that aluminium oxide is amphoteric.
…………………………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………………………. …………………………………………………………………………………………………………………………………. ……………………………………………………………………………………………………………………………. [3]
(d) Silicon(IV) oxide has a giant structure.
(i) Name the type of bonding in silicon(IV) oxide.
……………………………………………………………………………………………………………………… [1]
(ii) Give two physical properties of silicon(IV) oxide.
……………………………………………………………………………………………………………………………
……………………………………………………………………………………………………………………… [2]
(e) Calcium phosphate is used in fertilisers. The bonding in calcium phosphate is ionic. Calcium phosphate contains the phosphate ion, \(PO_4\)\
(i) What is ionic bonding?
…………………………………………………………………………………………………………………………… ……………………………………………………………………………………………………………………… [2]
(ii) Deduce the formula of calcium phosphate. ……………………………………………………………………………………………………………………… [1]
(f) Sulfur tetrafluoride, \(SF_4\), can be made by combining gaseous sulfur with fluorine.
\(S(g) + 2F_2(g) → SF_4(g)\)
The reaction is exothermic.
(i) Complete the energy level diagram for this reaction. Include an arrow which clearly shows the energy change during the reaction.
(ii) During the reaction the amount of energy given out is 780kJ/mol.
The F–F bond energy is 160kJ/mol.
Use this information to determine the bond energy, in kJ /mol, of one S–F bond in \(SF_4\).
……………………………. kJ/mol [3]
(g) Chlorine and compounds of chlorine are important in water treatment and in laboratory testing for water.
(i) Chlorine is added to water to make the water safe to drink.
Explain why adding chlorine makes water safe to drink.
……………………………………………………………………………………………………………………… [1]
(ii) A compound of chlorine is used in the laboratory to test for the presence of water.
Name the compound of chlorine used in this test and describe the colour change seen in a positive result of this test.
name of compound ……………………………………………………………………………………………….
colour change from …………………………………………… to ……………………………………………
[3]
(h) Argon is an unreactive noble gas.
(i) Explain why argon is unreactive.
……………………………………………………………………………………………………………………… [1]
(ii) Give one use of argon.
……………………………………………………………………………………………………………………… [1] [Total:27]
Answer/Explanation
2(a)
number of moles of \(NaNO_3\) used: 3.40/85 = 0.04(00) (mol)
OR
\(4.(00)× 10^–2 \)(mol);
number of moles of O2 formed: 0.04/2 = 0.02(00) (mol)
OR
\(2.(00)× 10^–2\) (mol);
volume of\( O_2\) formed: 0.02× 24 = 0.48\( (dm^3)\);
2(b)(i) (a substance which is) a proton/H+ /hydrogen ion acceptor; 1
2(b)(ii) \(Mg(s) + 2H_2O(l) → Mg(OH)_2(aq) + H_2(g)\)
\(Mg(OH)_2\); rest of equation;
2(c)
M1 add a named acid, e.g. HCl and a named alkali, e.g. NaOH;
M2 \(Al_2O_3\) will react with/neutralises both reagents;
M3 and so it will dissolve into the reagent/form a solution;
2(d)(i) covalent;
2(d)(ii) any 2 from: high melting point/high boiling point;
poor conductor (of electricity); hard; insoluble;
2(e)(i)
M1 (electrostatic) attraction;
M2 between oppositely charged ions;
2(e)(ii) \(Ca_3(PO_4)_2\);
2(f)(i)
M1 exothermic mark: horizontal product energy line at lower energy than that of reactant energy line;
M2 label of product mark: \(SF_4\);
M3 correct direction of vertical heat of reaction arrow: arrow must start level with reactant energy and finish level with product energy and must have only one (correct) arrow-head;
2(f)(ii)
M1 bond energy of \(2F_2: 2 × F–F = 2 × 160 = 320 (kJ/mol)\);
M2 bond energy of all bonds in SF4: 780 + 320 = 1100 (kJ/mol);
M3 calculated bond energy of \(SF_4\) divided by 4: 1100/4 = 275 (kJ/mol);
2(g)(i) kills bacteria;
2(g)(ii) name of compound: cobalt(II) chloride;
from: blue;
to: pink;
2(h)(i) it has a complete outer shell/a full outer shell/8 electrons in the outer shell; 1
2(h)(ii) (in) lamps;
Question
A student left a cube of ice on a plate in a warm room. The diagrams below show what happened
to the ice.
(a) Describe and explain what happened to the ice. In your answer,
• describe and explain the change of state which occurs,
• explain this change using the kinetic particle theory.
(b) Water is used in industry and in the home.
(i) Give one use of water in industry.
(ii) Give one use of water in the home.
(c) The symbol equation for the reaction of lithium with water is shown below.
\(2Li(s) + 2H_2O(l) → 2LiOH(aq) + H_2(g)\)
(i) Write the word equation for this reaction.
(ii) Describe two observations which can be made when lithium reacts with water.
(iii) Describe how the reactivity of potassium with water compares with the reactivity of lithium
with water.
(d) Ethanol can be made by the reaction of steam with ethene.
(i) Draw the structure of ethene showing all atoms and all bonds.
(ii) Describe the conditions required for this reaction.
(e) The table below describes the reaction of water or steam with different metals.
Answer/Explanation
Answer:
(a) melting/ ice melts / ice goes from solid to liquid;
any four from:
• in solid particles regularly arranged;
• in solid particles arranged in fixed position / cannot move;
• particles in solid absorb energy;
• particles (in solid) vibrate more / particles start to move when heated;
• forces between particles (in solid) broken;
• particles in liquid slide over each other / move;
• particles in liquid not regularly arranged;
(b) (i) coolant / for making ethanol / for making specified chemicals / solvent;
(ii) washing/ cooking/ cleaning etc.;
(c) (i) lithium + water → lithium hydroxide + hydrogen;
(ii) any two from:
• floats on surface (of water);
• bubbles of gas;
• fizzes / fizzing sound;
• decreases in size / disappears;
• moves around;
(iii) (potassium) more reactive / lithium less reactive;
(d) (i) correct structure of ethene;
(ii) high temperature;
catalyst/ phosphoric acid;
(e) cobalt → iron → cerium → calcium;
one pair reversed or all reversed = [1]