Page 1

Topic XII - Patterns in the Chemical World 1.

by Ricky Tsui

Periodic variations in physical properties of the elements from Li to Ar 

Revision: Structure of matter: 3GS + SMS (remember?)

Elements across a period: Metallic bond  Covalent bond Giant metallic structure  Giant covalent structure  Simple molecular structure

Matching: Li 

Be 

B 

C 

N 

O 

F 

Ne 

 Na

 Mg

 Al

 Si

 P

 S

 Cl

 Ar

How to describe the nature of bonding and structures? X has a __________________________________ structure, its ________ are held together by _________ _____________________________. O2 :

________________________________________________________________ ________________________________________________________________

Diamond:

________________________________________________________________ ________________________________________________________________

Mg:

________________________________________________________________ ________________________________________________________________

www.hksciblog.edublogs.org/dse-chem

Page 1


Topic XII - Patterns in the Chemical World 1.

by Ricky Tsui

Periodic variations in physical properties of the elements from Li to Ar (cont’d)

www.hksciblog.edublogs.org/dse-chem

Page 2


Topic XII - Patterns in the Chemical World 1.

by Ricky Tsui

Periodic variations in physical properties of the elements from Li to Ar (cont’d)

Melting points of first 20 elements

1.

Among the first 20 elements in the periodic table, which element has the lowest melting point? A. Hydrogen B. Helium C. Fluorine D. Neon

2. 1st statement Sodium has a higher melting point than sulphur

www.hksciblog.edublogs.org/dse-chem

2nd statement Sodium exists as giant lattice structure but sulphur exist as simple molecular structure.

Page 3


Topic XII - Patterns in the Chemical World 1.

by Ricky Tsui

Periodic variations in physical properties of the elements from Li to Ar (cont’d)

www.hksciblog.edublogs.org/dse-chem

Page 4


Topic XII - Patterns in the Chemical World 1.

by Ricky Tsui

Periodic variations in physical properties of the elements from Li to Ar (cont’d)

[05AL/I/1b/5 marks] Sketch the variation in electrical conductivity of the Period 3 elements from sodium to argon at room temperature and atmospheric pressure.

electrical conductivity

1. (b) (i)

11

(ii)

12

13

14 15 16 atomic number

17

18

Explain the variation in (i).

www.hksciblog.edublogs.org/dse-chem

Page 5


Topic XII - Patterns in the Chemical World 1.

by Ricky Tsui

Periodic variations in physical properties of the elements from Li to Ar (cont’d)

[10CE/MC]

[08CE/MC] 22. Comparing the elements in the second period of the Periodic Table, from lithium to fluorine, which of the following statements is/are correct? (1) (2) (3) A. B. C. D.

They show a gradual change from having metallic property to having non-metallic property. They show a gradual increase in the number of electron shells in their atoms. They show a gradual decrease in melting point. (1) only (2) only (1) and (3) only (2) and (3) only

[02AL/II/2c/9 marks] 2. (c) The graph below shows the variations of melting points and boiling points of the Period 3 elements. 3000

temperature / K ďƒ

o

o boiling point

2000 x

o o 1000

x

o

x melting point

o x

x

x o x

0 Na

Mg

Al

Si

P

S

Cl

ox Ar

Explain why (i) silicon, a metalloid, has a very high melting point; (ii)

the boiling points of the metals are in the order: Al > Mg > Na ;

www.hksciblog.edublogs.org/dse-chem

Page 6


Topic XII - Patterns in the Chemical World

by Ricky Tsui

(iii)

there is generally a larger difference between the melting point and the boiling point for metals than for non-metals;

(iv)

the melting point of sulphur is the highest among the non-metals. (9 marks)

[04CE/5/9 marks] 5.

Na2O, MgO, SiO2 and SO2 are oxides of Period 3 elements in the Periodic Table. Discuss how the melting points of these oxides are related to their bonding and structure. (9 marks)

www.hksciblog.edublogs.org/dse-chem

Page 7


Topic XII - Patterns in the Chemical World

by Ricky Tsui

[0CE/8(a)(i)/1 mark] 8. (a) A part of the Periodic Table is shown below :

(i)

Across a period, the elements demonstrate a gradual change in some of their physical properties. State ONE such property.

Concept-checking MC 1.

Among the first 20 elements in the periodic table, which element has the lowest melting point? A. B. C. D.

2.

Among the first 20 elements in the periodic table, which element has the highest melting point? A. B. C. D.

3.

Hydrogen Helium Fluorine Neon

Boron Aluminum Carbon Silicon

Which of the following elements are semi-metals? (1) Boron (2) Carbon (3) Aluminum (4) Silicon

www.hksciblog.edublogs.org/dse-chem

Page 8


Topic XII - Patterns in the Chemical World A. B. C. D. 4.

Sulphur is a solid but oxygen is a gas at room temperature. Sulphur has a giant covelent structure by oxygen has a simple molecular structure. The relative molecular mass of sulphur is greater than the relative molecular mass of oxygen. Both sulphur and oxygen can form ionic compound with sodium and covalent compound with hydrogen.

Which of the following elements is used in the manufacture of transisitors? A. B. C. D.

8.

Ar exists as monoatomic molecules Si exists as giant covalent structure Al exists as giant metallic structure C exists as simple molecular structure

Which of the following statements about oxygen and sulphur is incorrect? A. B. C. D.

7.

Si > C P>N Mg > Be Ar > Ne

Which of the following statements about the structures of elements is incorrect? A. B. C. D.

6.

(1) and (3) only (2) and (4) only (1) and (4) only (2) and (3) only

Which of the following about the melting points of period 2 and period 3 elements is incorrect? A. B. C. D.

5.

by Ricky Tsui

Silicon Carbon Magnesium Phosphorus

Which of the following elements exists as diatomic molecules at room temperature and pressure? A. B. C. D.

Phosphorus Sulphur Chlorine Argon

www.hksciblog.edublogs.org/dse-chem

Page 9


Topic XII - Patterns in the Chemical World 9.

10.

11.

Consider the group I and group II metals in the first 20 elements. Which of the following statements about the metals are correct? (1) (2) (3) (4)

Their melting points increase down the group. Their melting points increase across the period Their electrical conductivities increase down the group Their electrical conductivities increase across the period

A. B. C. D.

(1) and (3) only (2) and (4) only (1), (2) and (4) only (1), (2), (3) and (4)

Which of the following statements about certain period 2 and period 3 elements are correct? (1) (2) (3)

Magnesium is a metal but beryllium is not Silicon is a semi-metal but carbon is not Aluminum is a metal but boron is not

A. B. C. D.

(1) and (2) only (2) and (3) only (1) and (3) only (1), (2) and (3)

Which of the following represents an increasing order for the melting points of the three metals? A. B. C. D.

12.

Na < K < Mg K < Na < Mg Mg < K < Na Mg < Na < K

Consider the metals Na, K, Mg and Al. Which of them has the highest electrical conductivity? A. B. C. D.

13.

by Ricky Tsui

Na K Mg Al

Which of the following statements about the period 3 elements from Na to Si is correct? A. B. C. D.

Their melting points increase from Na to Si Their electrical conductivities increase from Na to Si Their densities increase from Na to Si Their solubility in water increase from Na to Si

www.hksciblog.edublogs.org/dse-chem

Page 10


Topic XII - Patterns in the Chemical World 14.

15.

Which of the following elements exist as a giant lattice structures at room temperature and pressure? (1) (2) (3) (4)

Lithium Beryllium Boron Carbon

A. B. C. D.

(1) and (4) only (2), (3) and (4) only (1), (3) and (4) only (1), (2), (3) and (4)

Which of the following statements about the melting points of the period 3 elements is incorrect? A. B. C. D.

16.

17.

by Ricky Tsui

Melting points increase from Na to Al Si has the highest melting point in the period Melting points decrease from Si to S Melting points decrease from S to Ar

Which of the following factors affect(s) the density of a gaseous element at room temperature and pressure? (1) (2) (3)

The relative molecular mass of the element The nature of bonding between the atoms in the molecule The magnitude of intermolecular forces

A. B. C. D.

(1) only (3) only (1) and (2) only (1), (2) and (3)

Which of the following statements about the dissolution of a period 3 element in water are correct? (1) (2) (3)

Sodium dissolves in water to form an alkaline solution. Phosphorus dissolves in water to form a neutral solution Chlorine dissolves in water to form an acidic solution

A. B. C. D.

(1) and (2) only (2) and (3) only (1) and (3) only (1), (2) and (3)

www.hksciblog.edublogs.org/dse-chem

Page 11


Topic XII - Patterns in the Chemical World 18.

1 B

by Ricky Tsui

The density of a solid metal depends on (1) (2) (3)

The strength of metallic bond The relative atomic mass of the element The packing of atoms in the solid

A. B. C. D.

(1) and (2) only (2) and (3) only (1) and (3) only (1), (2) and (3)

2 C

3 C

4 A

5 D

6 B

7 A

www.hksciblog.edublogs.org/dse-chem

8 C

9 B

10 B

11 B

12 D

13 A

14 D

15 C

16 A

17 C

18 D

Page 12


Topic XII - Patterns in the Chemical World 2.

by Ricky Tsui

Bonding, stoichiometric composition and acid-base properties of the oxides of elements from Na to Cl 

Bonding in Period 3 oxides 

Electronegativity: Li 1.0 Na 1.0

Be 1.5 Mg 1.2

B 2.0 Al 1.5

C 2.5 Si 1.8

N 3.0 P 2.1

O 3.5 S 2.5

F 4.0 Cl 3.0

EN between period 3 element and oxygen Element EN with O Oxide bonding Oxide m.p.(oC)

Na

Mg

Al

Si

P

S

Cl

920

2800

2045

1700

420

17

-92

EN  i____________ bond EN  c____________ bond

The melting points increase as the charges on the positive ion increase from 1+ in sodium to 3+ in aluminium. You would expect that the greater the charge, the greater the attractions. Unfortunately, the oxide with the highest melting and boiling point is magnesium oxide, not aluminium oxide! The reason for this probably lies in the increase in electronegativity as you go from sodium to magnesium to aluminium. That would mean that the electronegativity difference between the metal and the oxygen is decreasing. The smaller difference means that the bond won't be so purely ionic. It is also likely that molten aluminium oxide contains complex ions containing both aluminium and oxygen rather than simple aluminium and oxide ions.

* Aluminum oxide: ionic bond with c____________ c_______________ 

Stoichiometric composition in Period 3 oxides S Cl Sulphur Sodium Phosphorus dichlorine dioxide oxide / Magnesium Aluminum Silicon trioxide / oxide / Oxide / sodium oxide oxide dioxide phosphorus dichlorine name sulphur peroxide pentoxide heptoxide trioxide Oxide Na2O / P4O6 / SO2 / Cl2O / MgO Al2O3 SiO2 formula Na2O2 P4O10 SO3 Cl2O7

Element

Na

www.hksciblog.edublogs.org/dse-chem

Mg

Al

Si

P

Page 13


Topic XII - Patterns in the Chemical World 

Stoichiometric composition in Period 3 oxides (cont’d) Oxide formula

by Ricky Tsui

Na2O / Na2O2

MgO

Al2O3

SiO2

P4O6 / P4O10

SO2 / SO3

Cl2O / Cl2O7

Solubility and acid-base properties of Period 3 oxides (cont’d) Period 3 oxide Solubility in water Acid-base properties

Na2O / Na2O2

MgO

Al2O3

SiO2

P4O6 / P4O10

SO2 / SO3

Soluble

Slightly soluble

Insoluble

Insoluble

Soluble

Soluble

Basic

Basic

Amphoteric

Acidic

Acidic

Acidic

Cl2O / Cl2O7 Very soluble Acidic

O2-(aq) + H2O(l)  2OH-(l) Cl2O(g) + H2O(l)  2HOCl(aq) SO2(g) + 2NaOH(aq)  Na2SO3(aq) + H2O(l) P4O10(s) + 6H2O(l)  4H3PO4(aq) SiO2(s) + 2OH-(aq)  SiO32-(aq) + H2O(l) Al2O3(s) + 3H2SO4(aq)  Al2(SO4)3(aq) + 3H2O(l) Al2O3(s) + 2NaOH(aq) + 3H2O(l)  2NaAl(OH)4(aq) 

The trend is from strongly basic oxides on the left-hand side to strongly acidic ones on the right, via an amphoteric oxide (aluminium oxide) in the middle.

An amphoteric oxide is one which shows both acidic and basic properties.

www.hksciblog.edublogs.org/dse-chem

Page 14


Topic XII - Patterns in the Chemical World

by Ricky Tsui

[12DSE/MC]

[04CE/MC] 34.

Which of the following substances, when dissolved in water, gives a solution with pH greater than 7? (1) chlorine (2) calcium oxide (3) sulphur dioxide A. B. C. D.

(1) only (2) only (1) and (3) only (2) and (3) only

[12DSE/paper1/16/4 marks]

(a) Which of the oxides listed above can conduct electricity in molten state? (b) Explain why SiO2 has the highest melting point among the covalent oxides listed above.

(c) Write a chemical equation for the reaction between Al2O3(s) and NaOH(aq).

www.hksciblog.edublogs.org/dse-chem

Page 15


Topic XII - Patterns in the Chemical World

by Ricky Tsui

[08AL/paperII/1(b)/6 marks]

[06AL/paperI/1(a)/3 marks] 1.

(a)

The table below lists the melting points of three oxides of the Period 3 elements: Oxide Melting point / oC

Na2O 920

Al2O3 2040

SO2 ď&#x20AC;­75

Account for the large difference in the melting points of the three oxides.

www.hksciblog.edublogs.org/dse-chem

Page 16


Topic XII - Patterns in the Chemical World

by Ricky Tsui

[04CE/5/9 marks] 5.

Na2O, MgO, SiO2 and SO2 are oxides of Period 3 elements in the Periodic Table. Discuss how the melting points of these oxides are related to their bonding and structure. (9 marks)

Concept-checking MC 1.

Which of the following oxides is amphoteric? A. B. C. D.

2.

Which of the following oxides dissolve in water to give the most alkaline solution? A. B. C. D.

3.

Na2O MgO Al2O3 SiO2

Which of the following oxides dissolves in water to give the most acidic solution? A. B. C. D.

4.

Magnesium oxide Aluminum oxide Silicon dioxide Sulphur dioxide

Phosphorus(III) oxide Phosphorus(V) oxide Sulphur dioxide Sulphur trioxide

Which of the following oxides is the most soluble in water? A. B.

Sodium oxide Magnesium oxide

www.hksciblog.edublogs.org/dse-chem

Page 17


Topic XII - Patterns in the Chemical World C. D. 5.

6.

8.

(1) (2) (3)

Aluminum oxide dissolves in water to form an alkaline solution Aluminum oxide has a giant ionic structure Aluminum oxide is soluble both in hydrochloric acid and sodium hydroxide solution

A. B. C. D.

(1) only (3) only (1) and (2) only (2) and (3) only

Which of the following oxides is best used as an antacid? Sodium oxide Magnesium oxide Aluminum oxide Silicon dioxide

Which of the following oxides exist as simple molecular structures? (1) (2) (3) (4)

Aluminum oxide Silicon dioxide Sulphur dioxide Dichlorine oxide

A. B. C. D.

(1) and (2) only (2) and (3) only (3) and (4) only (1) and (4) only

Which of the following oxide is the most ionic? A. B. C. D.

9.

Carbon dioxide Silicon dioxide

Which of the following statements about aluminum oxide is / are correct?

A. B. C. D. 7.

by Ricky Tsui

Sodium oxide Aluminum oxide Phosphorus(V) oxide Dichlorine oxide

The oxidation number of Cl in Cl2O is A. B. C. D.

-2 -1 +1 +2

www.hksciblog.edublogs.org/dse-chem

Page 18


Topic XII - Patterns in the Chemical World 10.

The oxidation number of P in P4O10 is A. B. C. D.

11.

A Sodium Phosphorus Sulphur Chlorine

B Sodium peroxide Phosphorus(V) oxide Sulphur dioxide Dichlorine oxide

Element P, Q and R belong to period 3. P forms a basic oxide, Q forms an acidic oxide and R forms an amphoteric oxide. The atomic number of the three elements, when arranged in increasing order, should be A. B. C. D.

13.

-5 -3 +3 +5

Element A is a period 3 element. A burns in air to give an oxide B. The aqueous solution of B can turn potassium dichromate solution from orange to green. A and B are possibly

A. B. C. D. 12.

by Ricky Tsui

P<Q<R Q<P<R R<Q<P P<R<Q

Which of the following formulae are possible oxides of phosphorus? (1) (2) (3)

P2O5 P4O6 P4O10

A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

www.hksciblog.edublogs.org/dse-chem

Page 19


Topic XII - Patterns in the Chemical World 14.

Which of the following formulae are possible for oxides of chlorine? (1) Cl2O (2) ClO (3) Cl2O7 A. B. C. D.

15.

(1) and (2) (1) and (3) (2) and (3) (1), (2) and (3)

Which of the following statements about the oxides of period 3 elements is / are correct? (1) The melting points of the oxides increase from group I to group IV (2) The oxides change from basic to acidic across the period (3) The solubility of the oxides decreases across the period A. B. C. D.

16.

(1) only (2) only (1) and (2) only (1), (2) and (3)

Element X is in period 3. X ignites in air to form a solid oxide Y. Y dissolves in water to form an acidic solution. X may be A. B. C. D.

17.

Silicon Phosphorus Sulphur Chlorine

Z is an oxide of a period 3 element. Z is a liquid at room temperature and pressure. Z dissolves in water to form a strongly acidis solution. Z may be A. B. C. D.

18.

SiO2 P4O10 SO2 SO3

W is an oxide of a period 3 element. W dissolves in hydrochloric acid to form an aqueous solution which turns potassium iodide solution brown. W is probably A. B. C. D.

1 B

by Ricky Tsui

2 A

Na2O2 Na2O Al2O3 MgO 3 D

4 A

5 D

6 B

7 C

www.hksciblog.edublogs.org/dse-chem

8 A

9 C

10 D

11 C

12 D

13 C

14 B

15 B

16 B

17 D

18 A

Page 20


Topic XII - Patterns in the Chemical World 3.

by Ricky Tsui

General properties of transition metals Position of transition metals  from Period 4 to Period 7  

in between Group II and III

Most transition metals can exist in more than one

Oxidation states

oxidation states in their compounds

Sc

Ti

V

Cr

+3

+2 +3 +4

+2 +3 +4 +5

+2 +3 +4 +5 +6

+2 +3 +4 +5 +6 +7

+2 +3 +4 +5 +6

+2 +3

Ni +1 +2 +3 +4

Cu +1 +2

Zn +2

Most of the aqueous ions of transition metals are colored Titanium

 

Transition metals Mn Fe Co

Vanadium

Chromium

Manganese

Iron

Cobalt

Nickel

Copper

Ti3+

V2+

V3+

Cr3+

Cr2O72-

Mn2+

Mn3+

MnO4-

Fe2+

Fe3+

Co2+

Ni2+

Cu2+

purple

Purple

Green

Green

Orange

Pale pink

Red

Purple

Green

Yellow

Pink

Green

Blue

Not all aqueous transition metal ions are colored, Zn2+(aq) is colorless.

Transition metals and their compounds can be used as catalysts 

Haber process: manufacture of NH3(g), Fe(s) as catalyst N2(g) + 3H2(g)

Contact process: manufacture of H2SO4(l), vanadium (V) oxide, V2O5(s) as catalyst 2SO2(g) + O2(g)

2NH3(g)

2SO3(g)

Catalytic convertor: removal of nitrogen monoxide and carbon monoxide from exhausted gas of vehicles, Pt(s) as catalyst 2NO(g) + 2CO(g)  N2(g) + 2CO2(g)

Ziegler-Natta polymerization: manufacture of polythene, TiCl4(s) as catalyst

Decomposition of hydrogen peroxide, manganese (IV) oxide, MnO2(s) as catalyst 2H2O2(aq)  2H2O(l) + O2(g)

www.hksciblog.edublogs.org/dse-chem

Page 21


Topic XII - Patterns in the Chemical World ď&#x192;ź

by Ricky Tsui

Importance of transition metals

www.hksciblog.edublogs.org/dse-chem

Page 22


Topic XII - Patterns in the Chemical World 3.

by Ricky Tsui

General properties of transition metals (cont’d)

[04AL/II/2d/2 marks] 2(d)

‘Most iron(II) oxide samples have iron to oxygen mole ratios ranging from 0.84:1 to 0.96:1.’ Suggest why iron(II) oxide samples have variable compositions.

[04AL/II/3c/2 marks] 3(c)

(i)

Element X is a silvery-grey metal. Its relative atomic mass is smaller than 110. All isotopes of X are radioactive. X exhibits variable oxidation states, including +4, +5 and +7, in its compounds, and its highest possible oxidation state is +7. Referring to the Periodic Table, deduce what element X may be.

[05AL/II/2b/7 marks] 2(b)

The following three redox reactions take place at room temperature: (1) (2) (3)

KMnO4(s) reacts with concentrated HCl(aq) to give Cl2(g). Fe2+(aq) reacts with Cl2(g) to give Fe3+(aq). Acidified KMnO4(aq) is decolourised by SO2(g). (i)

Write a chemical equation for each of the three reactions described above.

(ii)

Is it possible to predict from the above information whether any reaction would occur in the following experiments ? Explain your answer. If it is possible to predict a reaction, write the chemical equation for the reaction. (I)

Adding FeSO4(aq) to acidified KMnO4(aq).

(II)

Passing SO2(g) into Fe3+(aq). (7 marks)

www.hksciblog.edublogs.org/dse-chem

Page 23


Topic XII - Patterns in the Chemical World

by Ricky Tsui

Concept-checking MC 1.

Mineral malachite is bluish green in color. Which of the following metal ions is responsible for its color? A. B. C. D.

2.

Which of the following metal ions is responsible for the green color of emerald? A. B. C. D.

3.

Fe2+ Co2+ Cu2+ Zn2+

Cr3+ Mn3+ Fe3+ Co3+

Which of the following reagents can convert an aqueous solution of Fe3+(aq) to Fe2+(aq)? (1) (2) (3)

SO2(aq) KI(aq) Cr3+(aq)

A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

www.hksciblog.edublogs.org/dse-chem

Page 24


Topic XII - Patterns in the Chemical World 4.

5.

6.

7.

by Ricky Tsui

Which of the following transition metal ions are colorless? (1) (2) (3) (4)

Fe2+ Zn2+ Sc3+ Cr3+

A. B. C. D.

(1) and (2) only (2) and (3) only (3) and (4) only (1) and (4) only

Transition metals or their compounds are commonly used as catalysts in industrial processes. Which of the following is / are wrongly matched?

(1) (2) (3)

Industrial process Haber process Ostwald process Contact process

A. B. C. D.

(1) only (2) only (3) only (1) and (2) only

Catalyst used Platinum Finely divided iron Vanadium(V) oxide

Which of the following reagents can convert MnO4- to Mn2+? (1) (2) (3) (4)

Cr2+ Fe2+ Cu2+ Zn2+

A. B. C. D.

(1) and (2) only (2) and (3) only (3) and (4) only (1) and (4) only

Which of the following metals has only one oxidation state in its compounds? A. B. C. D.

V Zn Ti Ni

www.hksciblog.edublogs.org/dse-chem

Page 25


Topic XII - Patterns in the Chemical World 8.

A patient is prescribed a medicine which contains iron (II) sulphate. What is the most probable disease that the patient has? A. B. C. D.

9.

11.

Co3+ Fe3+ MnO4Cr2O72-

Which of the following are the applications of nickel? (1) (2) (3)

To make stainless steel To make rechargeable battery To make coins

A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

Acidified potassium permanganate solution is commonly used as a standard solution in redox titrations. What indicator should be used for titration using acidified potassium permanganate solution? A. B. C. D.

12.

Fever Anaemia Arthritis Constipation

Which of the following ions is the strongest oxidizing agent among the four? A. B. C. D.

10.

by Ricky Tsui

Phenolphthalein Methyl orange Starch solution No indicator is needed

Which of the following radioisotopes is used as a source of radiation in radiotherapy? A. B. C. D.

Carbon-14 Nickel-59 Cobalt-60 Iron-55

www.hksciblog.edublogs.org/dse-chem

Page 26


Topic XII - Patterns in the Chemical World 13.

A bottle of iron(II) sulphate solution is suspected to contain traces amount of iron(II)) due to air oxidation. Which of the following reagents can be used to verify this? A. B. C. D.

14.

CrO3 Cr2O3 CrO4CrO42-

Which of the following metals has the highest oxidation number in one of its compounds? A. B. C. D.

17.

MnO2 MnCl2 Mn2O7 MnCl7

Which of the following ions / compounds does not exist? A. B. C. D.

16.

K3Fe(CN)6(aq) NaOH(aq) NH3(aq) KSCN(aq)

Which of the following compounds does note exist? A. B. C. D.

15.

by Ricky Tsui

Fe Co Ni Cu

The following reaction is catalyzed by Fe2+(aq). 2I-(aq) + S2O82-(aq) ď&#x192; 2SO42-(aq) + I2(aq) Which of the following statements about the above reaction are correct? (1) (2) (3)

Electron is transferred from I- to S2O82The reaction cannot proceed without the presence of Fe2+ Fe2+ is oxidized to Fe3+ and then reduced back to Fe2+ during the reaction

A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

www.hksciblog.edublogs.org/dse-chem

Page 27


Topic XII - Patterns in the Chemical World 18.

by Ricky Tsui

Nickel can be used as catalyst for the hydrogenation of a gaseous alkene, e.g. CH3CH=CH2(g) + H2(g) ď&#x192; CH3CH2CH3(g) Which of the following statements about the use of Ni in the above reaction is / are correct?

1 C

(1) (2) (3)

Ni participates in the chemical reaction Ni increases the rate of hydrogenation Ni provides a surface for the two gases to react

A. B. C. D.

(1) and (2) only (1) and (3) only (2) and (3) only (1), (2) and (3)

2 A

3 A

4 B

5 D

6 A

7 B

www.hksciblog.edublogs.org/dse-chem

8 B

9 C

10 D

11 D

12 C

13 D

14 D

15 C

16 A

17 B

18 C

Page 28


Topic XII - Patterns in the Chemical World

www.hksciblog.edublogs.org/dse-chem

by Ricky Tsui

Page 29

Topic 12 patterns in chemical world  
Read more
Read more
Similar to
Popular now
Just for you