Home / iGCSE Chemistry (0620) Theory (Core):2.4 Ions and ionic bonds: Exam Style Questions Paper 3

iGCSE Chemistry (0620) Theory (Core):2.4 Ions and ionic bonds: Exam Style Questions Paper 3- New Syllabus

iGCSE Chemistry Theory (Core) Paper 3 - All Chapters

Question

This question is about elements in different groups of the Periodic Table and their compounds.
(a) Silicon is in Group IV of the Periodic Table.
Explain why silicon is placed in Group IV.
Give your answer in terms of electronic configuration.
(b) Tin is also in Group IV of the Periodic Table.
Table 5.1 shows the melting point and the boiling point of tin.
Use Table 5.1 to deduce the physical state of tin at \( 175^{\circ}\mathrm{C} \).
Give a reason for your answer.
(c) Iodine is in Group VII of the Periodic Table.
Give the colour and state of iodine at room temperature and pressure.
(d) When a sample of calcium is added to a large container of cold water, a chemical reaction occurs.
(i) Describe what is observed when calcium is added to water.
(ii) Complete the word equation for the reaction of calcium with water.
(e) Dilute nitric acid is poured into a conical flask.
(i) Choose the pH value of dilute nitric acid.
Draw a circle around your chosen answer.
pH1        pH7        pH9        pH13
(ii) Complete the equation for the neutralisation of an acid to produce water.
State symbols are not required.
\( \mathrm{H}^{+} + \_\_\_\_\_ \longrightarrow \mathrm{H}_2\mathrm{O} \)
(iii) A few drops of methyl orange indicator are added to the flask containing dilute nitric acid.
Solid lithium carbonate is slowly added to the flask until the indicator changes colour.
State the colour change of the methyl orange indicator as the lithium carbonate is added to the dilute nitric acid in the flask.
(f) Lithium carbonate reacts with dilute nitric acid to form aqueous lithium nitrate.
Describe a test to show that \( \mathrm{Li}^{+} \) ions are present in the solution.
(g) Chlorine is in Group VII of the Periodic Table.
Chlorine reacts with lithium to form the ionic compound lithium chloride.
Complete the dot-and-cross diagram in Fig. 5.1 for lithium chloride to show:
  • the electronic configuration for each ion
  • the charge on each ion.
Use crosses to represent the electrons of lithium.

Most-appropriate topic codes (Cambridge IGCSE Chemistry 0620):

• Topic 8.1 — Arrangement of elements (Parts (a), (b), (c))
• Topic 9.1 — Properties of metals (Part (d))
• Topic 7.1 — The characteristic properties of acids and bases (Parts (e)(i), (e)(ii), (e)(iii))
• Topic 12.5 — Identification of ions and gases (Part (f))
• Topic 2.4 — Ions and ionic bonds (Part (g))

▶️ Answer/Explanation

(a)
It has 4 electrons in its outer electron shell.

Silicon (atomic number 14) has an electronic configuration of [2, 8, 4]. In the Periodic Table, the group number for elements in Groups I to VII equals the number of electrons in the outermost shell. Therefore, silicon belongs in Group IV.

(b)
Physical state: solid
Reason: Temperature is below the melting point.

The melting point of tin is 232°C. At 175°C, this temperature is less than the melting point; therefore, the heat energy is insufficient to break the metallic lattice bonds, and tin remains a solid.

(c)
Colour: grey-black
State: solid

At room temperature and pressure, iodine is a grey-black shiny solid. It sublimates upon heating to form a purple vapour.

(d)(i)
Any two from: sinks / effervescence (bubbles/fizzing) / solid gets smaller or disappears / temperature increases (heat produced) / white solid forms.

Calcium is a reactive metal, but it reacts less violently than sodium or potassium. It sinks in water, produces bubbles of hydrogen gas, gradually dissolves, generates heat, and produces a white precipitate of calcium hydroxide.

(d)(ii)
Calcium + water \( \rightarrow \) calcium hydroxide + hydrogen

The reaction produces a metal hydroxide and hydrogen gas, typical for active metals reacting with water.

(e)(i)
pH 1 circled

Dilute nitric acid is a strong acid, giving it a pH value of around 1 in a typical school laboratory concentration.

(e)(ii)
\( \mathrm{OH}^{-} \)

Neutralisation is the reaction between hydrogen ions (\( \mathrm{H}^{+} \)) from an acid and hydroxide ions (\( \mathrm{OH}^{-} \)) from an alkali to form water: \( \mathrm{H}^{+} + \mathrm{OH}^{-} \rightarrow \mathrm{H}_2\mathrm{O} \).

(e)(iii)
From red to yellow.

Methyl orange is red in acidic conditions. As lithium carbonate (a base) is added, it neutralises the acid. The indicator turns yellow when the solution becomes neutral or alkaline.

(f)
Test: Flame test
Observations: Red (flame) colour

Lithium ions (\( \mathrm{Li}^{+} \)) produce a distinctive crimson-red colour when a sample is introduced into a non-luminous Bunsen burner flame.

(g)


\( \mathrm{Li}^{+} \) ion: Drawn with no electrons (empty outer shell) and charge \( +1 \).
\( \mathrm{Cl}^{-} \) ion: Drawn with 8 electrons in the outer shell and charge \( -1 \).
The diagram uses crosses for lithium electrons and dots for chlorine electrons, showing electron transfer.

Lithium (2,1) loses one electron to become a positive ion, achieving the stable [2] configuration. Chlorine (2,8,7) gains that electron to become a negative ion, achieving the stable [2,8,8] configuration. The ions are held by strong electrostatic attraction.

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