Structure: Classification of Matter — Free IB Chemistry SL Practice Questions

1FoundationMCQIUPAC naming conventions for organic compounds1 markPaper 1~2 min

A compound has a continuous chain of six carbon atoms with a chlorine substituent and a methyl substituent. Numbering from one end gives these substituents at positions 3 and 4; numbering from the other end also gives positions 3 and 4. What is the correct IUPAC name for this compound?

Solutions

2MasteryMCQIsomerism and structural formulas1 markPaper 1~2 min

Three structural isomers exist for

\text{C}_3\text{H}_6\text{Br}_2

: 1,2-dibromopropane (bp

140\ ^\circ\text{C}

), 1,3-dibromopropane, and 2,2-dibromopropane (bp

132\ ^\circ\text{C}

). Which structural formula corresponds to the isomer with the lower boiling point, and what property best explains why its boiling point is lower than that of 1,2-dibromopropane?

Solutions

3MasteryMCQIUPAC naming conventions for organic compounds1 markPaper 1~2 min

A straight-chain alcohol has five carbon atoms with the hydroxyl group on the second carbon from the nearest chain end. Which of the following is the correct IUPAC name for this compound?

Solutions

4FoundationMCQIUPAC naming conventions for organic compounds1 markPaper 1~2 min

A straight-chain compound has the molecular formula

\text{C}_6\text{H}_{12}\text{O}_2

and contains a carboxylic acid functional group. What is the correct IUPAC name for this compound?

Solutions

5MasteryMCQIUPAC naming conventions for organic compounds1 markPaper 1~2 min

A branched-chain alcohol has a five-carbon main chain with a methyl substituent on the second carbon and a hydroxyl group on the third carbon. What is the correct IUPAC name for this compound?

Solutions

6FoundationMCQPeriodic trends: Atomic radius, ionization energy, electronegativity1 markPaper 1~2 min

Going down Group 1 from lithium to potassium, which statement correctly explains the trend in atomic radius?

Solutions

7MasteryMCQPeriodic trends: Atomic radius, ionization energy, electronegativity1 markPaper 1~2 min

Atomic radii of selected Period 2 elements are given: lithium = 152 pm and fluorine = 71 pm. Which value is most consistent with the atomic radius of beryllium?

Solutions

8MasteryMCQGroup classification of elements1 markPaper 1~2 min

An unknown element has the electron configuration

[\text{Ar}]4s^2

. To which group of the periodic table does this element belong?

Solutions

9FoundationMCQPeriodic trends: Atomic radius, ionization energy, electronegativity1 markPaper 1~2 min

The first ionization energies of Na, Mg, and Al are 496, 738, and 578 kJ mol

^{-1}

respectively. Which statement best explains why the first ionization energy of Al is lower than that of Mg?

Solutions

10MasteryMCQGroup classification of elements1 markPaper 1~2 min

An unknown metal reacts vigorously with water, producing hydrogen gas and a metal hydroxide solution. Its electron configuration is

[\text{Kr}]5s^1

. Which element is this unknown metal?

Solutions

11MasterySAQ-SIUPAC naming conventions for organic compounds5 marksPaper 2~8 min

A student is given the following organic compound:

\text{CH}_3\text{-CH(CH}_3\text{)-CH}_2\text{-CH}_2\text{-CH}_3

(a)

State the number of carbon atoms in the longest continuous carbon chain of this compound. [1 mark]

(b)

Determine the correct IUPAC name for this compound. Show the numbering of the parent chain that gives the lowest locant to the substituent. [2 marks]

(c)

A student proposes the alternative name 3-methylhexane for this compound. Explain, with reference to the lowest-locant rule, why this name is incorrect. [2 marks]

Solutions

12MasterySAQ-SIUPAC naming conventions for organic compounds5 marksPaper 2~8 min

A pharmaceutical chemist isolates a compound with the following structure:

\text{CH}_3\text{-CH}_2\text{-CH(OH)-CH}_2\text{-COOH}

(a)

State the suffix used in IUPAC naming for the highest-priority functional group present in this compound. [1 mark]

(b)

Determine the correct IUPAC name for this compound, identifying the parent chain and the locant of the hydroxyl substituent. [2 marks]

(c)

Explain why numbering the parent chain from the carboxyl end, rather than from the methyl end, gives the correct IUPAC name. [2 marks]

Solutions

13ChallengeSAQ-LIUPAC naming conventions for organic compounds8 marksPaper 2~12 min

Compounds X, Y, and Z are structural isomers with the molecular formula

\text{C}_6\text{H}_{12}\text{O}_2

. The following test results were obtained: - X gives a positive result with 2,4-dinitrophenylhydrazine (2,4-DNPH) but does not react with Tollens' reagent. - Y reacts with Tollens' reagent but does not react with 2,4-DNPH. - Z gives no reaction with either 2,4-DNPH or Tollens' reagent, but reacts with sodium metal to produce hydrogen gas. - Boiling points: X

= 128\,^\circ\text{C}

, Y

= 132\,^\circ\text{C}

, Z

= 164\,^\circ\text{C}

.

(a)

State the functional group present in each of X, Y, and Z. [1 mark]

(b)

Deduce the IUPAC name of one possible structure for each of X, Y, and Z. [3 marks]

(c)

Explain why the boiling point of Z is significantly higher than those of X and Y. [2 marks]

(d)

Explain why the three chemical tests described cannot uniquely identify the specific structural isomer present in each case, and state one analytical technique that could resolve this ambiguity. [2 marks]

Solutions

14MasterySAQ-SIUPAC naming conventions for organic compounds5 marksPaper 2~8 min

A student performs a bromine water test on an unknown organic compound with molecular formula

\text{C}_5\text{H}_{10}

. Rapid decolourisation is observed.

(a)

State the structural feature that causes rapid decolourisation of bromine water. [1 mark]

(b)

Deduce the IUPAC name of the compound, given that it has an unbranched carbon chain and the double bond is located between the second and third carbon atoms. Show the numbering scheme used. [2 marks]

(c)

The molecular formula

\text{C}_5\text{H}_{10}

is consistent with both an alkene and a cycloalkane. Evaluate, using both the bromine water result and the degree of unsaturation, whether the compound can be conclusively identified as an alkene. [2 marks]

Solutions

15MasterySAQ-SIUPAC naming conventions for organic compounds5 marksPaper 2~8 min

A student is given three isomeric compounds with the molecular formula

\text{C}_4\text{H}_{10}\text{O}

: butan-1-ol, butan-2-ol, and 2-methylpropan-2-ol.

(a)

State the length of the longest continuous carbon chain 2-methylpropan-2-ol. [1 mark]

(b)

Draw the full structural formula of butan-2-ol, clearly showing all bonds to the hydroxyl group. [2 marks]

(c)

Explain why the IUPAC name of 2-methylpropan-2-ol uses the prefix propan- rather than butan-, despite the molecule containing four carbon atoms, and deduce the locant used for the

-\text{OH}

group. [2 marks]

Solutions

16MasterySAQ-SPeriodic trends: Atomic radius, ionization energy, electronegativity5 marksPaper 2~8 min

This question is about the elements of Period 3.

(a)

State the trend in atomic radius across Period 3 from sodium to argon. [1 mark]

(b)

Explain why the first ionization energy of aluminium (

578\,\text{kJ mol}^{-1}

) is lower than that of magnesium (

738\,\text{kJ mol}^{-1}

), despite aluminium having a greater nuclear charge. [4 marks]

Solutions

17MasterySAQ-SPeriodic trends: Atomic radius, ionization energy, electronegativity5 marksPaper 2~8 min

This question is about electronegativity in Group 17. Element — Atomic number — Atomic radius / pm Chlorine — 17 — 99 Bromine — 35 — 114

(a)

State the trend in electronegativity down Group 17 from fluorine to iodine. [1 mark]

(b)

Using the data in the table, explain why chlorine has a higher electronegativity than bromine. [4 marks]

Solutions

18ChallengeSAQ-LPeriodic trends: Atomic radius, ionization energy, electronegativity7 marksPaper 2~11 min

Francium (Fr,

Z = 87

) is the heaviest alkali metal. Its hypothetical stable isotope Fr-223 has a predicted first ionization energy of

380\,\text{kJ mol}^{-1}

and an estimated atomic radius of

270\,\text{pm}

. Caesium (Cs,

Z = 55

), the alkali metal directly above Fr in Group 1, has a first ionization energy of

376\,\text{kJ mol}^{-1}

, an atomic radius of

265\,\text{pm}

, and an electronegativity of

0.79

on the Pauling scale. The effective nuclear charges are

Z_\text{eff}(\text{Cs}) = 2.51

and

Z_\text{eff}(\text{Fr}) = 2.20

.

(a)

Calculate the percentage difference in atomic radius and in first ionization energy between Fr and Cs, using Cs as the reference in each case. Give each answer to two significant figures. [2 marks]

(b)

Explain why the atomic radius of Fr is larger than that of Cs, despite Fr having more protons. Refer to effective nuclear charge and electron shells in your answer. [2 marks]

(c)

The Pauling scale assigns electronegativity values from bond dissociation energies of stable compounds. Using the ionization energy data provided, evaluate whether Fr is likely to be more or less electronegative than Cs, and assess the reliability of assigning a Pauling electronegativity to Fr. [3 marks]

Solutions

19MasterySAQ-SPeriodic trends: Atomic radius, ionization energy, electronegativity5 marksPaper 2~8 min

This question is about the elements beryllium and boron. Electronic configurations: Be:

1s^2 2s^2

; B:

1s^2 2p^1

(a)

State the general trend in first ionization energy across Period 2 from lithium to neon. [1 mark]

(b)

The first ionization energy of beryllium is

900\,\text{kJ mol}^{-1}

and that of boron is

801\,\text{kJ mol}^{-1}

. Explain why the first ionization energy of boron is lower than that of beryllium, despite boron having a greater nuclear charge. [4 marks]

Solutions

20MasterySAQ-SPeriodic trends: Atomic radius, ionization energy, electronegativity5 marksPaper 2~8 min

This question is about the elements of Group 1 (alkali metals).

(a)

State the trend in atomic radius down Group 1 from lithium to caesium. [1 mark]

(b)

Using the atomic radius data below, explain why the difference in first ionization energy between potassium and rubidium (

\Delta = 16\,\text{kJ mol}^{-1}

) is smaller than the difference between lithium and sodium (

\Delta = 24\,\text{kJ mol}^{-1}

). Element — First ionization energy /

\text{kJ mol}^{-1}

— Atomic radius / pm Lithium —

520

—

152

Sodium —

496

—

186

Potassium —

419

—

227

Rubidium —

403

—

248

[4 marks]

Solutions

Structure: Classification of Matter — Free Chemistry SL Practice Questions