Structure 3: Classification of matterIB Chemistry HL: Topic test

20 questions, 54 marks

IB Chemistry HL

Structure 3: Classification of matter topic test

Total 54 marks

Name

Class

Date

1
The atomic radii of the period 3 elements Na to Cl, in pm, are: Na 186, Mg 160, Al 143, Si 117, P 110, S 104, Cl 99.
(a)
What is the general trend in atomic radius across period 3 from sodium to chlorine, and what mainly causes it?
[1 mark]
AAtomic radius decreases across the period, because nuclear charge increases while electrons are added to the same principal energy level, so outer electrons are pulled in more strongly (shielding stays roughly constant)
BAtomic radius increases across the period, because more electrons are added, increasing electron–electron repulsion
CAtomic radius decreases across the period, because shielding increases faster than nuclear charge, reducing the effective attraction on outer electrons
DAtomic radius increases across the period, because each new electron occupies a new, higher principal energy level
(b)
Which statement correctly explains why the increase in nuclear charge across the period is not cancelled out by the extra electrons added?
[1 mark]
AThe extra electrons are added to a new, more distant shell, so they shield the nucleus very effectively
BThe extra electrons pair up in the same orbitals, cancelling most of the extra nuclear charge
CThe extra electrons are added to the same principal energy level (outer shell) as existing electrons and add little extra shielding, so the effective nuclear charge on the outer electrons increases
DThe extra electrons are removed from inner shells as the nuclear charge increases
(c)
Predict, with a reason, how the atomic radius of potassium (the first element of period 4) compares with that of sodium.
[2 marks]
Total for question 1: 4 marks
2
Compound Q has the structural formula CH₃CH₂CH₂COOH. Compound R is an isomer of Q with the structural formula CH₃CH₂COOCH₃, formed by esterification.
(a)
Which functional group is present in compound Q, CH₃CH₂CH₂COOH?
[1 mark]
AEster
BCarboxyl
CAldehyde
DEther
(b)
What is the IUPAC name of compound R, CH₃CH₂COOCH₃?
[1 mark]
AEthyl ethanoate
BPropyl methanoate
CMethyl butanoate
DMethyl propanoate
(c)
State the class of compound (homologous series) to which Q and R belong, and explain why Q and R are structural isomers rather than the same compound.
[2 marks]
Total for question 2: 4 marks
3
Aqueous nickel(II) sulfate solution contains the complex ion [Ni(H₂O)₆]²⁺, which is green and absorbs light most strongly at a wavelength of about 700 nm (red light). When excess ammonia solution is added, the complex ion [Ni(NH₃)₆]²⁺ forms, which is blue-purple and absorbs light most strongly at a wavelength of about 550–600 nm (yellow-green light).
(a)
Explain, in terms of the nickel(II) ion's d-sublevel, why [Ni(H₂O)₆]²⁺ is coloured.
[3 marks]
(b)
Explain why the colour changes from green to blue-purple when ammonia ligands replace water ligands, and deduce which complex has the larger energy gap between the split d-orbitals.
[4 marks]
Total for question 3: 7 marks
4
Ethylenediamine, H₂N–CH₂CH₂–NH₂, is an organic compound containing two amino functional groups. It can act as a ligand, using the lone pair on each nitrogen atom to form two coordinate bonds to a single copper(II) ion, giving the complex ion [Cu(NH₂CH₂CH₂NH₂)₂]²⁺, which is deep violet in colour.
(a)
Identify the functional group(s) and homologous series present in ethylenediamine, and explain why each nitrogen atom is able to donate a lone pair of electrons to form a coordinate bond.
[6 marks]
(b)
Explain, in terms of the copper(II) ion's electron configuration and the ligands bonded to it, why the [Cu(NH₂CH₂CH₂NH₂)₂]²⁺ complex is coloured.
[6 marks]
Total for question 4: 12 marks
5
Period 3 oxides show a trend in acid–base character: sodium oxide, Na₂O, and magnesium oxide, MgO, are basic; aluminium oxide, Al₂O₃, is amphoteric; silicon dioxide, SiO₂, is weakly acidic; and sulfur trioxide, SO₃, is strongly acidic. Sodium oxide and sulfur trioxide both react readily with water.
(a)
What are the products when sodium oxide reacts with water?
[1 mark]
ASodium carbonate and hydrogen gas
BSodium metal and hydrogen peroxide
CSodium hydroxide, a basic/alkaline solution
DSodium hydride and oxygen gas
(b)
What are the products when sulfur trioxide reacts with water?
[1 mark]
ASulfuric acid, H₂SO₄, an acidic solution
BSulfurous acid, H₂SO₃
CSulfur dioxide and oxygen gas
DHydrogen sulfide and ozone
(c)
Write a balanced equation for the reaction of sodium oxide with water, and state whether the resulting solution has a pH above or below 7.
[2 marks]
Total for question 5: 4 marks
6
Butan-2-ol has the structural formula CH₃CH(OH)CH₂CH₃. The carbon atom bonded to the hydroxyl group is also bonded to a hydrogen atom, a methyl group and an ethyl group.
(a)
Which carbon atom in butan-2-ol is a chiral centre, and why?
[1 mark]
AC1, because it is the terminal carbon
BC3, because it is next to the chiral centre
CNone of the carbons, because the molecule has no chiral centre
DC2, because it is bonded to four different groups: H, OH, CH₃ and C₂H₅
(b)
Which term describes the pair of non-superimposable mirror-image forms of butan-2-ol?
[1 mark]
AStructural isomers
BEnantiomers
CCis-trans isomers
DGeometric isomers
(c)
State one way in which the physical properties of the two enantiomers of butan-2-ol differ, and one way in which their chemical properties towards achiral reagents are the same.
[2 marks]
Total for question 6: 4 marks
7
The successive ionization energies of an unknown period 3 element, X, in kJ mol⁻¹, are: 1st 786, 2nd 1577, 3rd 3232, 4th 4356, 5th 16091, 6th 19785, 7th 23786, 8th 29252.
(a)
Deduce the group of the periodic table to which element X belongs, explaining your reasoning using the ionization energy data.
[3 marks]
(b)
State the full electron configuration expected for element X, assuming it is a period 3 element, and explain why removing the first four electrons requires increasing but relatively similar amounts of energy, while removing the fifth electron requires much more energy.
[4 marks]
Total for question 7: 7 marks
8
Sulfur trioxide, SO₃, reacts with water to form sulfuric acid, H₂SO₄, a strong inorganic acid. Ethanoic acid, CH₃COOH, is an organic carboxylic acid found in vinegar. Both solutions turn universal indicator red and react with magnesium metal to release hydrogen gas.
(a)
Explain, using the position of sulfur in the periodic table and the bonding in SO₃, why sulfur trioxide forms an acidic oxide when it reacts with water, whereas sodium (in the same period) forms a basic oxide.
[6 marks]
(b)
Explain, using the structure and bonding of ethanoic acid, why it also behaves as an acid in water, and evaluate whether ethanoic acid and sulfuric acid are equally strong acids at the same concentration.
[6 marks]
Total for question 8: 12 marks

End of questions