S3.

1 SL [85 marks]

1. [Maximum mark: 1] 24M.1A.SL.TZ1.8

Which oxide produces an aqueous solution with the highest pH?

A. Na2O

B. P 4O10

C. NO2

D. CO2 [1]

Markscheme

2. [Maximum mark: 1] 24M.1A.SL.TZ2.7

Which set of ions shows increasing ionic radii?

A. P 3− < Cl− < K+ < Ca2+

B. Cl− < P 3− < Ca2+ < K+

C. K+ < Ca2+ < P 3− < Cl−

D. Ca2+ < K+ < Cl− < P 3− [1]

Markscheme

D
3. [Maximum mark: 1] 24M.1A.SL.TZ2.8
When the same amount of each oxide is added to an equal volume of
water, which oxide produces the solution with the highest pH?

A. MgO

B. Al2O3

C. SiO2

D. SO2 [1]

Markscheme

4. [Maximum mark: 10] 24M.2.SL.TZ1.4

The water-gas shift reaction is another way to manufacture hydrogen.

CO (g) + H2O (g) ⇌ CO2 (g) + H2 (g) ΔH = −41 kJ mol−1

(a.i) State the oxidation state of carbon in carbon monoxide and

carbon dioxide.

[1] 

Markscheme

+2 AND +4 ✔
 Accept II/2 AND IV/4
Do not accept 2+ and 4+

(a.ii) Identify the oxidising and reducing agents, and the species
oxidised and reduced, in the forward reaction.

[2] 

Markscheme

✔✔

Award [1] for every two correct.

(b.i) Draw the Lewis structure of carbon dioxide.

[1] 

Markscheme

Accept any combination of dots and crosses or lines.

Ignore non linear drawing of correct Lewis structure.

(b.ii) Annotate the Lewis structure in (b)(i) to show the polarity of the
bonds by adding the symbols δ+ and δ- as appropriate. [1] 
 Markscheme

Accept only one correct δ+ and δ−

(b.iii) Explain the molecular geometry and polarity of the carbon

dioxide molecule. [2] 

Markscheme

linear AND two domains «repel» ✔

non-polar AND polar bonds cancel / symmetrical distribution of charge ✔

Accept OWTTE two domains

Accept non polar and no net dipole

Award [1] mark if correctly states “linear and non-polar" without correct explanations.

(b.iv) Outline why the increase in carbon dioxide concentration in the

atmosphere is of international concern. [2] 

Markscheme

CO2 greenhouse gas

OR
CO2 absorbs IR ✔

global warming/climate change

OR
 doesn’t cause local pollution, but acts on a global scale / OWTTE ✔

Accept ocean acidification for M2

(b.v) Explain, referring to the enthalpy profile shown, whether

carbon monoxide is more or less stable than carbon dioxide.

[1] 

Markscheme

less AND exothermic/energy released «combustion of CO to form CO2 »

OR
CO is less stable as it has a higher enthalpy ✔

Accept CO burns in air/oxygen

5. [Maximum mark: 3] 24M.2.SL.TZ1.5

(a) State the electron configuration of sulfur, S.
[1] 

Markscheme

1s2 2s2 2p6 3s2 3p4

OR
 [Ne] 3s2 3p4 ✔

Do not accept subscripts instead of superscripts

(b) State a physical property of sulfur which supports its

classification as a non-metal element. [1] 

Markscheme

Any one of:

insulator/non-conductor «of electricity/heat»
OR
brittle
OR
dull ✔

Accept other physical property.

Do not accept answers based on electron configuration

(c) Suggest a balanced equation for the reaction of an oxide of

sulfur with water. [1] 

Markscheme

SO2 + H2O → H2SO3

OR
SO3 + H2O → H2SO4 ✔

6. [Maximum mark: 8] 24M.2.SL.TZ2.3

The acid-base character of the oxides of elements depends on their position in
the periodic table.
(a.i) State one environmental problem caused by sulfur dioxide,
SO2. [1]

Markscheme

acid rain/deposition
OR
smog ✔

Accept any specific environmental problem caused by acid deposition or smog.

(a.ii) Write an equation to show how sulfur dioxide reacts in the

atmosphere to produce a secondary pollutant. [1]

Markscheme

2SO2 (g) + O2 (g) → 2SO3 (g)

OR
SO2 (g) + H2O (l) → H2SO3 (aq)
OR
2SO2 (g) + 2H2O (l) + O2 (g) → 2H2SO4 (aq) ✔

(b) A solution was prepared by dissolving 0.100 mol of sodium

oxide in distilled water and making the total volume up to 1.00
dm3.

(b.i) Write the equation for the reaction between sodium oxide and
water. [1]

Markscheme

H2O (l) + Na2O (s) → 2NaOH (aq) ✔

(b.ii) Calculate the pH of the solution. [2]

 Markscheme

«[OH−] = 2 x 0.100 = 0.200 mol dm−3»

Alternative One:
−14

[H+] = « 1.00×10
0.200
= » 5.00 × 10−14 «mol dm−3» ✔

«pH=−log5.00 × 10−14 =» 13.30 ✔

Alternative Two:

«pOH = −log 0.200 =» 0.699 ✔

«pH = 14.00 − 0.699 =» 13.30 ✔

(c) Phosphoric acid, H3PO4, also reacts with water.

H3PO4 (aq) + H2O (l) ⇌ H3O+ (aq) + H2PO4−(aq)

(c.i) State an expression for the equilibrium constant, Kc, for this
equation. [1]

Markscheme

+ −
[H 3 O ][H 2 PO ]
«Kc=» ✔
4

[H 3 PO 4 ]

(c.ii) State, with a reason, the effect of an increase in temperature on

the position of this equilibrium, assuming ΔH⦵ < 0. [1]

Markscheme

shifts to the left/toward reactants AND «forward» reaction is exothermic

OR
 shifts to the left/toward reactants AND favours endothermic «reverse»
reaction ✔

(d) Outline why the ionic radius of the phosphide ion, P 3−, is
greater than that of the sulfide ion, S2−. [1]

Markscheme

same electron configuration AND P 3− has smaller nuclear charge/number of

protons/atomic number ✔

Accept “same «number of» electrons/shells” OR “same shielding" for “same electron configuration”.

Accept “P3− has smaller effective nuclear charge” for “P3− has smaller nuclear charge”.

7. [Maximum mark: 1] 23N.1A.SL.TZ1.6

Which electron configuration represents a d‑block element in the
ground state?

A. 1s22s22p63s23p64s13d1

B. 1s22s22p63s23p64s13d10

C. 1s22s22p63s23p64s23d9

D. 1s22s22p63s23p64s13d104p1 [1] 

Markscheme

8. [Maximum mark: 1] 23N.1A.SL.TZ1.8

 Which factor generally increases when first ionization energy
increases?

A. Atomic radius

B. Electronegativity

C. Metallic character

D. Nuclear charge [1] 

Markscheme

9. [Maximum mark: 1] 23N.1A.SL.TZ1.9

The periodic table provided shows 118 elements. Which group of
elements would a new element with atomic number 119 be most
similar to?

A. Alkali metals

B. Halogens

C. Lanthanoids and actinoids

D. Noble gases [1] 

Markscheme

10. [Maximum mark: 1] 23N.1A.SL.TZ1.14

Which reactions release heat?
 I. C(s) + O2 (g) → CO2 (g)

II. Na+ (g) + e− → Na (g)

III. NH3 (g) → NH3 (l)

A. I and II only

B. I and III only

C. II and III only

D. I, II and III [1] 

Markscheme

11. [Maximum mark: 1] 23N.1A.SL.TZ2.6

Which electron configuration represents a d‑block element in the
ground state?

A. 1s22s22p63s23p64s13d1

B. 1s22s22p63s23p64s13d10

C. 1s22s22p63s23p64s23d9

D. 1s22s22p63s23p64s13d104p1 [1] 

Markscheme

12. [Maximum mark: 1] 23N.1A.SL.TZ2.8

 Which factor generally increases when first ionization energy
increases?

A. Atomic radius

B. Electronegativity

C. Metallic character

D. Nuclear charge [1] 

Markscheme

13. [Maximum mark: 1] 23N.1A.SL.TZ2.9

The periodic table provided shows 118 elements. Which group of
elements would a new element with atomic number 119 be most
similar to?

A. Alkali metals

B. Halogens

C. Lanthanoids and actinoids

D. Noble gases [1] 

Markscheme

14. [Maximum mark: 1] 23N.1A.SL.TZ2.14

Which reactions release heat?
 I. C(s) + O2 (g) → CO2 (g)

II. Na+ (g) + e− → Na (g)

III. NH3 (g) → NH3 (l)

A. I and II only

B. I and III only

C. II and III only

D. I, II and III [1] 

Markscheme

15. [Maximum mark: 14] 23N.2.SL.TZ1.2

Methanoic acid can be produced by the hydrogenation of carbon dioxide
according to the equilibrium

CO2 (g) + H2 (g)⇌HCOOH (g)

(a) Explain why this process has been extensively investigated in

recent years. [2] 

Markscheme

it removes CO2 «from the atmosphere» ✓

CO2 is a «major» contributor to climate change / global warming

OR
CO2 is a greenhouse gas ✓

Accept reduces CO2 emissions for M1.

 Award [1] for reactants are cheap/readily available.

Award [1] for atom economy is 100%.

Award [1] for methanoic acid can be used to manufacture other useful products.

Award [1] for reference to depletion of fossil fuels as a source of organic chemicals.

(b) State the equilibrium constant expression for this reaction.

[1] 

Markscheme

[HCOOH]
«K 𝑐 = » [CO 2 ][H 2 ]
✓

(c) Bond enthalpies are a useful way of finding approximate

enthalpy changes for reactions.

(c.i) Determine the enthalpy change, ΔH⦵, of this reaction, using

section 11 of the data booklet. [3] 

Markscheme

ALTERNATIVE 1

«bond breaking» C=O + H-H / 804 + 436 / 1240 «kJ»✓

«bond forming» C-H + C-O + O-H / 414 + 358 + 463 / 1235 «kJ» ✓

ΔH «= 1240 − 1235» = «+» 5 «kJ mol−1» ✓

ALTERNATIVE 2

«bond breaking» 2C=O + H-H / 2(804) + 436 / 2044 «kJ» ✓

«bond forming» C=O + C-H + C-O + O-H / 804 + 414 + 358 + 463 / 2039 «kJ»
✓ΔH «= 2044 − 2039» = «+»5 «kJ mol−1» ✓
 Award [3] for correct final answer.

(c.ii) Assuming a 0.1 % uncertainty for each bond enthalpy,

determine the resultant percentage uncertainty of the
calculated enthalpy change of the reaction. [2] 

Markscheme

ALTERNATIVE 1

sum of absolute uncertainties « = 0.804 + 0.436 + 0.414 + 0.358 + 0.463 = »

2.475 «kJ mol−1» ✓

percentage uncertainty « = 100 × 2.475

5
= 49.5 % = » 50 «%» ✓

ALTERNATIVE 2

sum of absolute uncertainties « = 3(0.804) + 0.436 + 0.414 + 0.358 + 0.463 =

»
4.083 «kJ mol−1» ✓

percentage uncertainty « = 100 × 4.083

5
= 81.7 % » = 80 «%» ✓

Award [2] for correct final answer.

(c) Deduce how the value of Kc would be affected by increases in

temperature. [1] 

Markscheme

Kc increases AND endothermic

OR
Kc increases AND «equilibrium» shifts to the right ✓
(d) The conversion of carbon dioxide to methanoic acid is usually
carried out over an iridium‑based catalyst.

(d.i) Sketch, on the axes provided, energy profiles of the reaction

both with and without a catalyst, indicating Δ H and the
activation energies.

[3] 

Markscheme

two curves, each passing through a maximum AND same finishing point ✓

endothermic enthalpy change labelled ✓

both activation energies correctly labelled ✓

 Do not penalize curve showing multiple steps for the catalysis in M1.

Accept double-headed arrows or lines in M2 and M3.

Accept Ecat for catalysed Ea in M3.

Award [1 max] for one curve drawn and correctly labelled.

(d.ii) State one change, other than carrying out the reaction over a
catalyst at high temperature, that would increase the reaction
rate. [1] 

Markscheme

increase pressure ✓

Accept increase «reactant» concentration but not increase amount of reactant.

(e) Determine the oxidation state of carbon in methanoic acid.

[1] 

Markscheme

+2 ✓

Do not accept 2 or 2+.

16. [Maximum mark: 14] 23N.2.SL.TZ2.2

Methanoic acid can be produced by the hydrogenation of carbon dioxide
according to the equilibrium

CO2 (g) + H2 (g)⇌HCOOH (g)

(a) Explain why this process has been extensively investigated in
recent years. [2] 

Markscheme

it removes CO2 «from the atmosphere» ✓

CO2 is a «major» contributor to climate change / global warming

OR
CO2 is a greenhouse gas ✓

Accept reduces CO2 emissions for M1.

Award [1] for reactants are cheap/readily available.

Award [1] for atom economy is 100%.

Award [1] for methanoic acid can be used to manufacture other useful products.

Award [1] for reference to depletion of fossil fuels as a source of organic chemicals.

(b) State the equilibrium constant expression for this reaction.

[1] 

Markscheme

[HCOOH]
« K 𝑐 =» [CO 2 ][H 2 ]
✓

(c) Bond enthalpies are a useful way of finding approximate

enthalpy changes for reactions.

(c.i) Determine the enthalpy change, ΔH⦵, of this reaction, using

section 12 of the data booklet. [3] 

Markscheme
 ALTERNATIVE 1

«bond breaking» C=O + H-H / 804 + 436 / 1240 «kJ»✓

«bond forming» C-H + C-O + O-H / 414 + 358 + 463 / 1235 «kJ» ✓

ΔH⦵ « = 1240 − 1235» = «+»5 «kJ mol−1» ✓

ALTERNATIVE 2

«bond breaking» 2C=O + H-H / 2(804) + 436 / 2044 «kJ» ✓

«bond forming» C=O + C-H + C-O + O-H / 804 + 414 + 358 + 463 / 2039 «kJ»
✓

ΔH⦵ « = 2044 − 2039» = «+» 5 «kJ mol−1» ✓

Award [3] for correct final answer.

(c.ii) Assuming a 0.1 % uncertainty for each bond enthalpy,

determine the resultant percentage uncertainty of the
calculated enthalpy change of the reaction. [2] 

Markscheme

ALTERNATIVE 1

sum of absolute uncertainties « = 0.804 + 0.436 + 0.414 + 0.358 + 0.463 = »

2.475 «kJ mol−1» ✓

percentage uncertainty « = 100 × 2.475

5
= 49.5 % = » 50 «%» ✓

ALTERNATIVE 2

sum of absolute uncertainties « = 3(0.804) + 0.436 + 0.414 + 0.358 + 0.463 =

»
4.083 «kJ mol−1» ✓
 percentage uncertainty « = 100 × 4.083

5
= 81.7 % » = 80 «%» ✓

Award [2] for correct final answer.

(c) Deduce how the value of Kc would be affected by increases in

temperature. [1] 

Markscheme

Kc increases AND endothermic

OR
Kc increases AND «equilibrium» shifts to the right ✓

(d) The conversion of carbon dioxide to methanoic acid is usually

carried out over an iridium‑based catalyst.

(d.i) Sketch, on the axes provided, energy profiles of the reaction

both with and without a catalyst, indicating Δ H and the
activation energies.

[3] 

Markscheme
 two curves, each passing through a maximum AND same finishing point ✓

endothermic enthalpy change labelled ✓

both activation energies correctly labelled ✓

Do not penalize curve showing multiple steps for the catalysis in M1.

Accept double-headed arrows or lines in M2 and M3.

Accept Ecat for catalysed Ea in M3.

Award [1 max] for one curve drawn and correctly labelled.

(d.ii) State one change, other than carrying out the reaction over a
catalyst at high temperature, that would increase the reaction
rate. [1] 

Markscheme

increase pressure ✓
 Accept increase «reactant» concentration but not increase amount of reactant.

(e) Determine the oxidation state of carbon in methanoic acid.

[1] 

Markscheme

+2✓

Do not accept 2 or 2 +.

17. [Maximum mark: 1] 22N.1A.SL.TZ0.6

What is the relative atomic mass of a sample of chlorine containing 70
% of the 35Cl isotope and 30 % of the 37Cl isotope?

A. 35.4

B. 35.5

C. 35.6

D. 35.7 [1]

Markscheme

18. [Maximum mark: 1] 22N.1A.SL.TZ0.7

Which elements are considered to be metalloids?

I. Gallium
 II. Germanium

III. Arsenic

A. I and II only

B. I and III only

C. II and III only

D. I, II and III
[1]

Markscheme

19. [Maximum mark: 1] 22N.1A.SL.TZ0.8

Which property of elements increases down a group but decreases
across a period?

A. Atomic radius

B. Electronegativity

C. Ionic radius

D. Ionization energy [1]

Markscheme

A
20. [Maximum mark: 7] 22N.2.SL.TZ0.5
Lignite, a type of coal, contains about 0.40 % sulfur by mass.

(a) Calculate the amount, in mol, of sulfur dioxide produced when

500.0 g of lignite undergoes combustion.

S (s) + O2 (g) → SO2 (g) [2] 

Markscheme

«0. 40% × 500. 0 g =» 2.0 «g» ✔

«2. 0 g × = 0. 062 mol of S » = 0.062 «mol of SO2» ✔

1 mol S

32.07 g

Award [2] for correct final answer.

Accept 0.063 «mol».

(b) Write an equation that shows how sulfur dioxide can produce
acid rain. [1] 

Markscheme

SO2 (g) + H2O (l) → H2SO3 (aq)

OR

SO2 (g) + ½O2 (g) → SO3 (g) AND SO3 (g) + H2O (l) → H2SO4 (aq)

OR

SO2 (g) + ½O2 (g) + H2O (l) → H2SO4 (aq) ✔

 Accept ionized forms of acids.

(c) Sodium thiosulfate reacts with hydrochloric acid as shown:

Na2S2O3 (aq) + 2HCl (aq) → S (s) + SO2 (aq) + 2NaCl (aq) + H2O
(l)

The precipitate of sulfur makes the mixture cloudy, so a mark

underneath the reaction mixture becomes invisible with time.

Suggest two variables, other than concentration, that should be

controlled when comparing relative rates at different
temperatures. [2] 

Markscheme

Any two of:

depth/volume «of solution» ✔

colour/darkness/thickness/size/background of mark ✔

intensity of lighting in the lab ✔

 Accept same size flask.

Accept position of observation/person observing.

Accept same equipment/apparatus.

Do not accept catalyst/particle size/pressure/time.

(d) Discuss two different ways to reduce the environmental impact

of energy production from coal. [2] 

Markscheme

Any two of:

remove sulfur from coal ✔

add lime during combustion ✔

not allow sulfur oxides to be released into the environment ✔

reduce proportion/percentage of energy/power produced by «the

combustion of» coal ✔

Accept any valid method to wash coal and remove sulfur content for M1.

Accept any valid combustion/post-combustion method to remove sulfur oxides.

Accept any suggestion that would reduce the amount of coal that is burnt or would reduce the damage
caused.

Do not accept answers that only reduce production of SO2/CO2 from other fuels.

Accept “improve efficiency of energy production from coal”.

 Accept “use coal of lower sulfur content” OR “cleaner coal”.

21. [Maximum mark: 15] 19M.2.HL.TZ2.4

Rhenium, Re, was the last element with a stable isotope to be isolated.

Before its isolation, scientists predicted the existence of rhenium and some of its
properties.

One chloride of rhenium has the empirical formula ReCl3.

Rhenium forms salts containing the perrhenate(VII) ion, ReO4−.

(a) The stable isotope of rhenium contains 110 neutrons.

State the nuclear symbol notation A X for this isotope.

[1] 
Z

Markscheme

185
75
Re [✔]

(b(i)) Suggest the basis of these predictions.

[2] 

Markscheme

gap in the periodic table

OR
element with atomic number «75» unknown
OR
break/irregularity in periodic trends [✔]

«periodic table shows» regular/periodic trends «in properties» [✔]

(b(ii)) A scientist wants to investigate the catalytic properties of a thin
layer of rhenium metal on a graphite surface.

Describe an electrochemical process to produce a layer of

rhenium on graphite. [2] 

Markscheme

electrolyze «a solution of /molten» rhenium salt/Ren+ [✔]

graphite as cathode/negative electrode

OR
rhenium forms at cathode/negative electrode [✔]

Note: Accept “using rhenium anode” for M1.

(b(iii)) Predict two other chemical properties you would expect

rhenium to have, given its position in the periodic table. [2] 

Markscheme

Any two of:

variable oxidation states [✔]

forms complex ions/compounds [✔]

coloured compounds/ions [✔]

«para»magnetic compounds/ions [✔]

Note: Accept other valid responses related to its chemical metallic properties.

Do not accept “catalytic properties”.

(c) Describe how the relative reactivity of rhenium, compared to
silver, zinc, and copper, can be established using pieces of
rhenium and solutions of these metal sulfates. [2] 

Markscheme

place «pieces of» Re into each solution [✔]

if Re reacts/is coated with metal, that metal is less reactive «than Re» [✔]

Note: Accept other valid observations such as “colour of solution fades” or “solid/metal appears” for
“reacts”.

(d(i)) State the name of this compound, applying IUPAC rules.

[1] 

Markscheme

rhenium(III) chloride
OR
rhenium trichloride [✔]

(d(ii)) Calculate the percentage, by mass, of rhenium in ReCl3.

[2] 

Markscheme

«Mr ReCl3 = 186.21 + (3 × 35.45) =» 292.56 [✔]

«100 × 186.21

292.56
=» 63.648 «%» [✔]

(e(i)) Suggest why the existence of salts containing an ion with this
formula could be predicted. Refer to section 7 of the data
booklet. [1] 
 Markscheme

same group as Mn «which forms MnO4-»

OR
in group 7/has 7 valence electrons, so its «highest» oxidation state is +7
[✔]

(e(ii)) Deduce the coefficients required to complete the half-equation.

ReO4− (aq) + ____H+ (aq) + ____e− ⇌ [Re(OH)2]2+ (aq) +

____H2O (l) Eθ = +0.36 V [1] 

Markscheme

ReO4− (aq) + 6H+ (aq) + 3e− ⇌ [Re(OH)2]2+ (aq) + 2H2O (l) [✔]

(e(iii)) Predict, giving a reason, whether the reduction of ReO4− to

[Re(OH)2]2+ would oxidize Fe2+ to Fe3+ in aqueous solution. Use
section 24 of the data booklet. [1] 

Markscheme

no AND ReO4− is a weaker oxidizing agent than Fe3+

OR
no AND Fe3+ is a stronger oxidizing agent than ReO4−
OR
no AND Fe2+ is a weaker reducing agent than [Re(OH)2]2+
OR
no AND [Re(OH)2]2+ is a stronger reducing agent than Fe2+
OR
no AND cell emf would be negative/–0.41 V [✔]
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