Structure 3: Classification of matterIB Chemistry SL: Topic test

20 questions, 54 marks

IB Chemistry SL

Structure 3: Classification of matter topic test

Total 54 marks

Name

Class

Date

1
Gallium (Z = 31) and krypton (Z = 36) are both period 4 elements.
(a)
Which block of the periodic table does gallium belong to?
[1 mark]
As-block
Bp-block
Cd-block
Df-block
(b)
How many valence (outer main energy level) electrons does krypton have?
[1 mark]
A2
B6
C8
D18
(c)
Deduce the full electron configuration of gallium, and use it to identify gallium's group number.
[2 marks]
Total for question 1: 4 marks
2
The first ionization energies, in kJ mol⁻¹, of four period 2 elements are: lithium 520, beryllium 899, boron 801 and carbon 1086.
(a)
Which best explains why carbon has a much higher first ionization energy than lithium?
[1 mark]
Acarbon has a much greater nuclear charge than lithium, while the shielding from inner (1s²) electrons is essentially the same in both, so carbon's outer electron is attracted more strongly to the nucleus
Bcarbon has a larger atomic radius so its outer electron is easier to remove
Ccarbon's outer electron experiences a greater shielding effect from a fully-filled inner shell
Dcarbon's nuclear charge is smaller than lithium's
(b)
What is the general trend in first ionization energy across period 2, from lithium to neon, and why?
[1 mark]
Ait decreases, because atomic radius decreases
Bit increases overall, because nuclear charge increases while electrons are added to the same main energy level
Cit stays constant, because the number of energy levels does not change
Dit increases, because electrons are added to a new, higher energy level
(c)
Explain why beryllium has a higher first ionization energy than lithium.
[2 marks]
Total for question 2: 4 marks
3
A chemist has an organic compound with the condensed structural formula CH3CH(OH)CH2COOH, a four-carbon molecule.
(a)
This molecule contains two functional groups. Name both functional groups present, and identify the homologous series to which the compound most specifically belongs (the one defined by the higher-priority group).
[3 marks]
(b)
Give the IUPAC name of CH3CH(OH)CH2COOH, and describe its full structural formula in words, showing every atom and bond.
[4 marks]
Total for question 3: 7 marks
4
A student compares four organic compounds, each with an ethyl or ethane-derived backbone: ethane (CH3CH3), ethanol (CH3CH2OH), ethanal (CH3CHO) and ethanoic acid (CH3COOH).
(a)
Deduce the oxidation state of the functional-group carbon atom (the second carbon in each of ethanol, ethanal and ethanoic acid; either carbon in ethane) in each of the four compounds, and state the trend in oxidation state across the series from ethane to ethanoic acid.
[6 marks]
(b)
State the homologous series and general formula of each of ethanol, ethanal and ethanoic acid, and explain, in terms of functional groups and intermolecular forces, why ethanoic acid has a much higher boiling point than ethanal, even though both contain the same number of carbon atoms.
[6 marks]
Total for question 4: 12 marks
5
Aqueous chlorine is added to separate solutions of potassium iodide and potassium fluoride. Separately, a small piece of potassium metal is dropped into a trough of water.
(a)
What is observed when aqueous chlorine is added to potassium iodide solution?
[1 mark]
Ano reaction occurs
Ba white precipitate of KI forms
Chydrogen gas bubbles are released
Dthe solution turns orange/brown as iodine is displaced
(b)
Why does no reaction occur between aqueous chlorine and potassium fluoride solution?
[1 mark]
Afluorine is more reactive/more electronegative than chlorine, so chlorine cannot displace fluoride from solution
Bpotassium fluoride is insoluble in water
Cfluoride ions are too large to react with chlorine
Dchlorine only reacts with metals, not halide ions
(c)
Write a balanced equation for the reaction between potassium metal and water, and state one visible observation of the reaction.
[2 marks]
Total for question 5: 4 marks
6
Potassium oxide, carbon dioxide and aluminium oxide are each tested for their acid–base behaviour. Potassium oxide and carbon dioxide both dissolve in water; aluminium oxide does not dissolve in water but reacts with both dilute acid and dilute alkali.
(a)
What is the pH of the solution formed when potassium oxide dissolves in water?
[1 mark]
ApH < 7, because it forms an acidic solution
BpH ≈ 7, because it forms a neutral solution
CpH > 7, because it forms an alkaline solution
DpH cannot be determined without more data
(b)
Which term describes the behaviour of aluminium oxide?
[1 mark]
Abasic
Bacidic
Cneutral
Damphoteric
(c)
Deduce a balanced equation, with state symbols, for the reaction of potassium oxide with water, and state the oxidation state of oxygen in potassium oxide.
[2 marks]
Total for question 6: 4 marks
7
A student is given the molecular formula C4H8 and asked to describe all the non-cyclic structural isomers that are alkenes (ignoring cis-trans isomerism), and separately considers C4H10O as a set of possible alcohols and ethers.
(a)
Describe, in words, the structures of the three non-cyclic structural isomers of C4H8 that are alkenes, and state which pair of these isomers are position isomers of each other.
[3 marks]
(b)
Give the structure (in words) and IUPAC name of one straight-chain alcohol with molecular formula C4H10O, the structure and name of one ether with molecular formula C4H10O, and state the general term used to describe two compounds, like these, that share a molecular formula but have their atoms bonded together in different arrangements or with different functional groups.
[4 marks]
Total for question 7: 7 marks
8
The Pauling electronegativity values of the period 3 elements sodium to chlorine increase steadily from 0.9 (sodium) to 3.2 (chlorine) as atomic number increases. Separately, the boiling points of the first four straight-chain carboxylic acids are: methanoic acid 101 °C, ethanoic acid 118 °C, propanoic acid 141 °C, butanoic acid 164 °C.
(a)
Explain, in terms of atomic structure, why electronegativity increases from sodium to chlorine across period 3, and explain why electronegativity generally decreases down a group, such as from chlorine to iodine.
[6 marks]
(b)
State the homologous series and general formula of these compounds, and explain, in terms of structure and intermolecular forces, why the boiling point increases steadily from methanoic acid to butanoic acid.
[6 marks]
Total for question 8: 12 marks

End of questions