Question
The diagrams show part of the structures of five substances, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ and $\mathbf{E}$.
(a) Answer the following questions about these structures.
Each structure may be used once, more than once or not at al
l.
(i) Which two of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, are covalently bonded? [2]
(ii) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is a diatomic molecule? [1]
(iii) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is a compound? [1]
(iv) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is very soluble in water? [1]
(v) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is used in cutting tools? [1]
(vi) Which one of these structures, $\mathbf{A}, \mathbf{B}, \mathbf{C}, \mathbf{D}$ or $\mathbf{E}$, is used in electrical wiring? [1]
(b) Substance $\mathbf{B}$ is an element.
What is meant by the term element? [1] [Total: 8]
▶️Answer/Explanation
Ans:
(a)(i) B / diamond (1)
D / nitrogen / N2 (1)
(a)(ii) D / nitrogen / N2
(a)(iii) C / lithium chloride / LiCl
(a)(iv) C / lithium chloride / LiCl
(a)(v) B / diamond
(a)(vi) E / copper / Cu
(b) substance in which all the atoms have the same proton number / substance containing (only) one type of atom
Question
(a) A list of formulae is shown.
$\begin{aligned} & \mathrm{AlCl}_3 \\ & \mathrm{CaCO}_3 \\ & \mathrm{CO} \\ & \mathrm{CO}_2 \\ & \mathrm{CoCl}_2 \\ & \mathrm{CuSO}_4 \\ & \mathrm{MgCl}_2 \\ & \mathrm{~N}_2 \\ & \mathrm{NaCl}_2 \\ & \mathrm{NH}_3 \\ & \mathrm{O}_2 \\ & \mathrm{SO}_2\end{aligned}$
Answer the following questions using these formulae.
Each formula may be used once, more than once or not at all.
State which formula represents:
(i) a compound that changes colour from white to blue when water is added
(ii) a compound that is used to make cement
(iii) an element that forms 78% of clean, dry air
(iv) a compound that contains an ion with a single positive charge
(v) a compound that dissolves in water to form an alkaline solution.
(b) Complete the dot-and-cross diagram to show the electron arrangement in a molecule of ammonia.
(c) State whether magnesium oxide is a basic oxide or an acidic oxide. Give a reason for your answer.
Answer/Explanation
Answer:
(a) (i) \(CuSO_4\)
(ii) \(CaSO_3\)
(iii) \(N_2\)
(iv) NaCl
(v) \(NH_3\)
(b) bonding pair of electrons between the N atom and each of the H atoms with no other electrons on the H atom (1)
2 non-bonding electrons on N atom (1)
(c) basic oxide AND magnesium is a metal / metal oxides are basic (1)
Question
(a) The structures of four substances C, D, E and F, are shown.
(i) Which one of these substances, C, D, E or F, is a gas at room temperature?
(ii) What type of bonding is present in substance E?
(iii) Which one of these substances, C, D, E or F, is soluble in water?
(iv) Which one of these substances, C, D, E or F, conducts electricity when solid?
(b) The halogens have molecules containing two atoms.
What is the name for molecules containing only two atoms?
(c) The reaction of iodine with hydrogen is shown.
\(I_2 + H_2 \leftrightarrow 2HI\)
What is the meaning of the symbol \(\leftrightarrow\)?
(d) Iodine is formed when chlorine reacts with aqueous potassium iodide.
(i) Complete the chemical equation for this reaction.
\(………. + 2KI → I_2 + …….KCl\)
(ii) When aqueous iodine is mixed with aqueous potassium chloride, there is no reaction.
Suggest, in terms of chemical reactivity, why there is no reaction.
Answer/Explanation
Answer:
(a) (i) F
(ii) ionic
(iii) E
(iv) D
(b) diatomic
(c) reversible reaction / the reaction can go forwards or backwards
(d) (i) \(Cl_2\) (on left) (1)
2 (KCl) (on right) (1)
(ii) chlorine is more reactive than iodine / iodine is less reactive than chlorine