Question
This question is about the first 30 elements in the Periodic Table.
Name the element which:
(a) is 78% of clean, dry air [1]
(b) has atoms with an electronic structure of 2,8,1 [1]
(c) is extracted from hematite [1]
(d) forms an oxide with a giant covalent structure [1]
(e) is the gas with the slowest rate of diffusion at room temperature[1]
(f) has an anhydrous chloride which turns pink when water is added[1]
(g) has aqueous ions which form a white precipitate when added to aqueous silver ions[1]
(h) forms a blue hydroxide which dissolves in aqueous ammonia[1]
(i) is added to molten iron to remove impurities in the steel making process[1]
(j) is used to galvanize iron. [1] [Total: 10]
Answer/Explanation
Ans:
1(a) nitrogen
1(b) sodium
1(c) iron
1(d) silicon
1(e) chlorine
1(f) cobalt
1(g) chlorine
1(h) copper
1(i) oxygen
1(j) zinc
Question
A student adds excess large pieces of magnesium carbonate, MgCO3, to dilute hydrochloric acid, HCl, and measures the volume of carbon dioxide gas, CO2, given off.
(a) Add the missing state symbols to the chemical equation for the reaction.
MgCO3 ….. + 2HCl….. → MgCl 2(aq) + H2O ….. + CO2 ….. [1]
(b) Complete the dot-and-cross diagram to show the electron arrangement of the ions in magnesium chloride.
The inner shells have been drawn.
Give the charges on the ions.[3]
(c) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of carbon dioxide.
Show outer shell electrons only.[2]
(d) The graph shows how the volume of carbon dioxide gas changes with time.
(i) Describe how the graph shows that the rate of this reaction decreases as time increases.[1]
(ii) Explain, in terms of particles, why the rate of this reaction decreases as time increases.[2]
(iii) The student repeats the experiment using powdered MgCO3 instead of large pieces.
All other conditions stay the same.
On the grid, draw the line expected when powdered MgCO3 is used instead of large pieces. [2]
(e) Determine the volume of CO2 gas given off when excess MgCO3 is added to 25.0cm3 of 0.400mol/dm3 HCl at room temperature and pressure.
MgCO3 + 2HCl → MgCl2 + H2O + CO2
Use the following steps.
- Calculate the number of moles of HCl in 25.0cm3 of 0.400mol/dm3 of acid.
mol
- Determine the number of moles of CO2 gas given off.
mol
- Calculate the volume of CO2 gas given off in cm3.
cm3 [3] [Total: 14]
Answer/Explanation
Ans:
2(a) MgCO3(s) + 2HCl(aq) → MgCl2(q) + H2O(l) + CO2(g)
2(b) eight crosses in second shell of Mg
7 dots and 1 cross in third shell of both Cl
2+ charge on Mg and – charge on both Cl ions on correct answer line
2(c) C atom double bonded to 2 O atoms
4 non-bonding e– on each O and no non-bonding e– on C and both octets complete
2(d)(i) gradient (of line) decreases
2(d)(ii) concentration of particles (of acid) decreases
lower rate of collisions of particles
2(d)(iii) a new line steeper than printed line and starts at origin and levels off earlier than printed line
levels off at the same volume
2(e) M1 mol HCl = 0.400 × 25.0 / 1000 = 0.01(00)
M2 mol CO2 = M1 / 2 = 0.0100 / 2 = 0.005(00)
M3 volume CO2 = M2 × 24000 = 120 (cm3)
Question
Nitrogen dioxide, NO2, is an atmospheric pollutant and is formed in car engines.
(a) Explain how nitrogen dioxide is formed in car engines. [2]
(b) Nitrogen dioxide causes respiratory problems.
State one other adverse effect of nitrogen dioxide.[1]
(c) Nitrogen dioxide emissions can be reduced by adding an aqueous solution of urea, (NH2)2CO, to car exhaust gases.
The heat of the exhaust gases breaks down the urea into simpler substances.
(i) Name the type of reaction which occurs when a substance is heated and breaks down into simpler substances.[1]
(ii) One molecule of urea breaks down to form one molecule of ammonia and one other molecule.
Complete the chemical equation to show the formula of the other molecule formed in this reaction.
(NH2)2CO → NH3 + [1]
(iii) State the test for ammonia.[2]
test
observations
(d) The ammonia formed reacts with nitrogen dioxide to form nitrogen and water.
(i) Balance the equation for this reaction.
NO2 + NH3 → N2 + 12H2O [2]
(ii) State how the equation shows that the nitrogen in nitrogen dioxide is reduced.[1]
(iii) This reaction is a redox reaction.
State the meaning of the term redox.[1]
(e) 135 moles of urea, (NH2)2CO, is stored in the tank of a car.
Calculate the mass, in kg, of the stored (NH2)2CO.
mass of (NH2)2CO = kg [2]
(f) Another oxide of nitrogen formed in car engines is nitrogen monoxide, NO. A catalytic converter removes NO by reacting it with a gas formed by incomplete combustion of the fuel. Two non‑toxic gases are formed.
(i) Name the gas formed by incomplete combustion of the fuel.[1]
(ii) Name the two non‑toxic gases formed. and [1] [Total: 15]
Answer/Explanation
Ans:
3(a) nitrogen (from air) and oxygen (from air) react
react due to high temperatures (of engine)
3(b) acid rain
3(c)(i) (thermal) decomposition
3(c)(ii) HCNO
3(c)(iii) (damp red) litmus
(litmus) turns blue
3(d)(i) 6NO2 8NH3 7N2
either 6NO2 or 8NH3
all three balanced
3(d)(ii) (nitrogen) loses oxygen
3(d)(iii) reduction and oxidation occur
3(e) Mr urea = 60
135 × 60 = 8100 and g to kg conversion = 8.1(00) kg
3(f)(i) carbon monoxide
3(f)(ii) carbon dioxide and nitrogen
Question
This question is about chemical reactions and electricity.
(a) The diagram shows the apparatus used in the production of electrical energy in a simple cell.
The zinc electrode dissolves in the electrolyte forming Zn2+(aq) ions.
(i) Draw an arrow on the diagram to show the direction of electron flow. [1]
(ii) Write the ionic half-equation for the reaction that occurs when the zinc electrode dissolves.[2]
(b) The reading on the voltmeter can be increased if either zinc or iron is replaced by another metal.
(i) Name a metal that can replace zinc and increase the reading on the voltmeter.[1]
(ii) Name a metal that can replace iron and increase the reading on the voltmeter.[1]
(c) Fuel cells are used to generate electricity.
(i) Name the reactants in a fuel cell.[1]
(ii) Name the waste product of a fuel cell.[1]
(d) Electricity can be used to break down aqueous or molten ionic compounds.
(i) Name the process which uses electricity to break down aqueous or molten ionic compounds.[1]
(ii) Explain why the ionic compound needs to be aqueous or molten.[1]
(e) Brine is concentrated aqueous sodium chloride.
(i) Name three substances which are manufactured by passing electricity through brine. [3]
1
2
3
(ii) Name a different substance formed when molten sodium chloride is used instead of concentrated aqueous sodium chloride.[1] [Total: 13]
Answer/Explanation
Ans:
4(a)(i) arrow going from Zn to Fe
4(a)(ii) Zn → Zn2+ + 2e–
Zn as only reactant and Zn2+ as only product
correct equation
4(b)(i) any metal above zinc in reactivity series
4(b)(ii) any metal below iron in reactivity series
4(c)(i) hydrogen and oxygen
4(c)(ii) water
4(d)(i) electrolysis
4(d)(ii) mobile ions
4(e)(i) hydrogen
chlorine
sodium hydroxide
4(e)(ii) sodium
Question
This question is about alkanes and alkenes.
(a) Short-chain alkanes and alkenes can be formed from long-chain alkanes in a chemical reaction.
(i) Name the type of chemical reaction which forms short‑chain alkanes and alkenes from long‑chain alkanes.[1]
(ii) Decane has 10 carbon atoms. It forms ethane and ethene as the only products in this type of chemical reaction.
Write the chemical equation for this reaction.[3]
(b) Ethane reacts with chlorine at room temperature to form chloroethane, C2H5Cl, and one other product.
(i) Name the other product formed.[1]
(ii) State the condition needed for this reaction to take place.[1]
(c) Ethene reacts with chlorine at room temperature to form dichloroethane, C2H4Cl2.
C2H4 + Cl2 → C2H4Cl2
(i) State why this is an addition reaction.[1]
(ii) The chemical equation for this reaction can be represented as shown.
The energy change for the reaction is –180kJ/mol.
Use the bond energies in the table to calculate the bond energy of a C–Cl bond, in kJ/mol.
Use the following steps.
step 1 Calculate the energy needed to break bonds.
energy needed to break bonds = kJ
step 2 Use your answer in step 1 and the energy change for the reaction to determine the energy released when bonds are formed.
energy released when bonds form = kJ
step 3 Use your answer in step 2 and bond energy values to determine the energy of a C–Cl bond.
bond energy of a C–Cl bond = kJ/mol
[4][Total: 11]
Answer/Explanation
Ans:
5(a)(i) cracking
5(a)(ii) C10H22 → 4C2H4 + C2H6
C10H22 as only reactant
formulae of ethene and ethane as only products
correct equation
5(b)(i) hydrogen chloride
5(b)(ii) ultraviolet light
5(c)(i) (only) one product is formed
5(c)(ii) M1 Bond energy in breaking bonds
= [(4 × 410) + 610 + 240] = 2490 (kJ / mol)
M2 Use of total E change to find bond energy of C2H4Cl2
= M1 + 180 = 2490 + 180 = 2670 (kJ / mol)
M3 Determination of total C–Cl bond energy
= M2 – [(4 × 410) + 350] = 2670 – 1990 = 680 (kJ / mol)
M4 Determination of each C–Cl bond energy
= M3 / 2 = 680 / 2 = 340 (kJ / mol)
Question
The names of four esters are listed.
methyl propanoate
ethyl propanoate
propyl propanoate
butyl propanoate
(a) Esters are a family of organic compounds with similar chemical properties. They can be represented by the formula CnH2nO2.
(i) State the name given to a family of organic compounds with similar chemical properties.[1]
(ii) Explain why members of a family of organic compounds have similar chemical properties.[1]
(iii) State the name given to a formula such as CnH2nO2.[1]
(iv) Determine the value of ‘n’ in butyl propanoate.[1]
(b) All four of the esters in the list are liquids at room temperature.
Name the technique used to separate ethyl propanoate from a mixture of the four esters.[2]
(c) All four esters can be made by reacting different alcohols with the same substance.
(i) Name this substance and draw its structure. Show all of the atoms and all of the bonds.[2]
name
structure
(ii) Name the alcohol used to make methyl propanoate.[1]
(d) Other esters, not in the list, have the same molecular formula as propyl propanoate, but different structures.
(i) State the term used to describe substances with the same molecular formula but different structures.[1]
(ii) Name two esters with the same molecular formula as propyl propanoate.[2]
1
2
(e) Polyesters can be made from the two different molecules shown.
(i) Complete the diagram to show a section of the polyester made from these two molecules. Include all of the atoms and all of the bonds in the linkages.[3]
(ii) Name the type of polymerization that takes place when this polymer forms.[1]
(iii) Name a polyester.[1] [Total: 17]
Answer/Explanation
Ans:
6(a)(i) homologous series
6(a)(ii) Same functional group
6(a)(iii) general (formula)
6(a)(iv) 7
6(b) fractional
distillation
6(c)(i) propanoic acid
structure of propanoic acid
6(c)(ii) methanol
6(d)(i) structural isomers
6(d)(ii) ethyl butanoate
butyl ethanoate
6(e)(i) any correct displayed ester link between any two blocks showing all atoms and all bonds
correct orientation of three displayed inter-block ester links with correct orientation
continuation bonds on polyester
6(e)(ii) condensation
6(e)(iii) terylene