The Periodic Table: Chemical Periodicity

The Periodic Table: Chemical Periodicity

Mark Scheme 8

Level International A Level Subject Chemistry Exam Board CIE Topic The Periodic Table: Chemical PeriodicitySub-Topic Paper Type Theory Booklet Mark Scheme 8

Time Allowed:

Score:

64 minutes

/53

Percentage: /100

Grade Boundaries:

A* A B C D E U

>85% 777.5% 70% 62.5% 57.5% 45% <45%

Dr. Asher Rana www.chemistryonlinetuition.com [email protected]

1 (a (i) A complex is a compound / molecule / species / ion formed by a central metal atom / ionsurrounded by / bonded to one or more ligands / groups/ molecules / anions [1]

A ligand is a species that contains a lone pair of electrons that forms a dative bond to a metal atom / ion / or a lone pair donor to metal atom / ion [1]

(ii)

H2O

Cu

H2O OH2

OH2

H2O

H2O

2+

and

Cl

Cl

Cu

Cl

Cl

2-

correct 3D structures: octahedral and tetrahedral

[1]1] +[1]

(iii)

H3N

Pt

Cl Cl

NH3H3N

Pt

Cl NH3

Cl

or

Cl

Pt ClH3N

NH3

NH3

Pt ClCl

NH3

or

[1] both structures geometric or cis-trans [1]

(b)b) Cu(II) is [Ar] 3d9 [1]Cu(I) is [Ar] 3d10 [1]

(ii) Cu(II): d orbitals / subshell are split (in ligand field) and

electron moves from lower to upper orbital or an electron is promoted / excited

in doing so it absorbs a photon / light [2]

Cu(I): no gap in upper orbital / all orbitals are full [1]

[2]

[1]

ndo

(c) (i) ∆Ho = +2 × 33.2 – 157.3 + 302.9 = (+) 212 kJ mol–1 ecf

(ii) ∆Ho = –168.6 + 2 × 157.3 = (+)146 kJ mol–1 allow ecf from (c)(i)

high T / temperature since ∆H is positive / endothermic

[Total: 16]


Cl I

(1) (1) (1) (1)

(1)(1)1)

2 (a penalise (-1) the use of names of elements or formulae of compounds

(i) Ca(ii) O or N or C

(iii) C or N or S or F or Cl or Br(iv) Si or Ge or B

(v) Al or Si or P or S or H

(vi) Al

(b) (i)

elementelem Mg Al Sii S

oxideo MgOxi 2OO Al2O3 SiO2 P2O5/P4O10

or P2O3/P4O6

SO2

flame yellow

or orange

hite wwhitew whitewhite

or yellow

blue

(1) formula of oxide colour of flame (1)

(ii)

chloride NaCl MgCl2 AlCl3

or

Al2Cl6 SiCl4

PCl3

or

PCl5

SCl2 or

S2Cl2

HpH6.5 to 6.9

1 to 4

(1) formula of chloride pH of solution formed (1) [4]

(c) (i)

(1)

(1)

(1)

(1)

(ii) intermolecular forces/van der Waals’ forces

are stronger or greater in ICl

ICl has most electrons orhas the largest permanent dipole

(iii) ICl

greatest difference in electronegativity is between I and Cl (1)1)

[Total: 15]


3 (a (i) the enthalpy change/released when 1 mole is formed [1]

of ionic lattice from the gas phase ions [1]

(ii) Mg2+ + O2– → MgO [1] [3]

(b) measurements needed:[1] [1] [1]

volume/mass/weight of water (in calorimeter)initial + final temperature/temperature change/temperature rise (of the water)mass of Mg (used)/mass MgONot volume/moles/mass of oxygen used

[3]

(c) ∆H = 148 + 736 + 1450 + 496/2 - 141 + 798 – 3791 = –552 kJ mol–1 [3]

[3]

(d) Na2O(s) + H2O(aq/l) → 2NaOH(aq) [1]

[1]MgO(s) + H2O(aq/l) → Mg(OH)2(s) or Mg(OH)2(aq)pH 12.5-14 [NaOH] AND 8-10.5 [Mg(OH)2] respectively [1]

[3]

[Total: 12]


4 (a)

element particle formula

copperopperCu2+

allow Cu+

argon orrgon molecule Ar

one mark for each correct row or column (2 × 1) [2]

(b) Cu cations held in ‘sea’ of delocalised electrons (1)by strong metallic bonds (1)

Ar van der Waals’ forces between molecules (1) which are weak (1) [4]

(c) (i) oxidising agent or electron acceptor (1)Ar has very high first I.E or Ea for reaction is very high or Ar has full valency shell/complete octet (1) [2]

(d) from Ne to Xe more electrons in atom (1)hence more induced dipoles/van der Waals’ forces (1) [2]

[Total: 10]


The Periodic Table: Chemical Periodicity

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