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(a) Ionic and covalent bonds both involve an electrostatic attraction between different species. Identify the species that are electrostatically attracted to one another in:
• an ionic bond
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• a covalent bond
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(b) Complete Table 1.1 to show the total numbers of protons and electrons in the molecular ions $\text{NH}_4^+$, $\text{CO}_3^{2-}$ and $\text{PO}_4^{3-}$.
[Table_1]
(c) $\text{NH}_4^+$ is a Br\o nsted–Lowry acid.
(i) Define Br\o nsted–Lowry acid.
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[1]
(ii) When $\text{NH}_4^+$ (aq) is heated with NaOH(aq), a pungent gas is produced.
Write an ionic equation for this reaction.
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[1]
(iii) The nitrogen atom in $\text{NH}_4^+$ is sp$^3$ hybridised. sp$^3$ orbitals form from the mixing of one 2s and three 2p orbitals.
Sketch the shapes of a 2s and a 2p$_x$ orbital on the axes in Fig. 1.1.
(d) There are many naturally occurring hydrated compounds that contain the anion $\text{PO}_4^{3-}$.
(i) Name the anion $\text{PO}_4^{3-}$.
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[1]
(ii) Struvite is a soft hydrated mineral with $M_r = 245.3$. The anhydrous form of the mineral has the formula $\text{NH}_4\text{MgPO}_4$.
Calculate the number of molecules of water of crystallisation in struvite. Give your answer to the nearest integer. Show your working.
number of molecules of water of crystallisation = .......................
[2]
(e) OH$^-$(aq) reacts with 2-bromo-2-methylpropane in an S$_N$1 reaction. The molecular ion (CH$_3$)$_3$C$^+$ forms as the intermediate in this reaction.
(i) Draw the mechanism for the S$_N$1 reaction of OH$^-$ with 2-bromo-2-methylpropane. Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate. Draw the structures of the organic reactant and organic product.
[3]
(ii) 2-bromo-2-methylpropane is a tertiary bromoalkane.
Define tertiary bromoalkane.
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[1]
(iii) Organic compound M forms when 2-bromo-2-methylpropane is heated with ethanolic OH$^-$.
Draw the structure of M.
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(a) Complete Table 2.1.
• Identify the bonding shown by each chloride under standard conditions.
Use C = covalent, I = ionic, M = metallic.
• Identify the structure shown by each chloride under standard conditions.
Use G = giant, S = simple.
• Deduce the oxidation state of the Period 3 element in each chloride.
[4]
[Table_1]
(b) Write equations for the reactions of NaCl and PCl_5 with water.
Include state symbols in both equations.
NaCl ...................................................................................................
PCl_5 ...................................................................................................[3]
(c) In the gas phase, AlCl_3(g) exists at equilibrium with Al_2Cl_6(g) as shown.
equation 1 $2AlCl_3(g) \rightleftharpoons Al_2Cl_6(g)\quad \Delta H_r = -63\text{kJ mol}^{-1}$
(i) Complete the dot-and-cross diagram to show the bonding in A$_2$Cl$_6$.
[2]
(ii) State the effect of an increase in temperature on the equilibrium mixture in equation 1.
Explain your answer.
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[1]
(d) A 3.30 g sample of a Period 3 chloride is heated to 500 K in a sealed flask.
At this temperature, the chloride is a gas of volume 250 cm$^3$ and the pressure in the flask is 323 kPa.
Use the ideal gas equation $pV = nRT$ to calculate the $M_r$ of the Period 3 chloride.
Deduce its formula.
$M_r = \quad\text{...........................}$
formula of Period 3 chloride = ...........................[3]
(e) (i) An excess of Cl$^-$(aq) is added to 1 cm$^3$ of Br$_2$(aq).
Describe what is observed. Explain your answer.
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[2]
(ii) SiCl$_2$ has $M_r = 103.1$ and is a liquid at room temperature. SBr$_2$ has $M_r = 191.9$ and is a gas at room temperature.
Explain the difference in the physical state of SiCl$_2$ and SBr$_2$. Give your answer in terms of intermolecular forces.
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[2]
(f) Bismuth is a dense metal in the same group as phosphorus.
(i) Draw a labelled diagram to show the bonding in bismuth metal.
[2]
(ii) Bismuth reacts with chlorine to form BiCl$_3$.
BiCl$_3$ is a solid at room temperature. It melts when heated gently.
BiCl$_3$ reacts vigorously with water at room temperature to form an acidic solution.
Suggest the type of bonding and structure shown by BiCl$_3$. Explain your answer.
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[2]
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(a) Table 3.1 shows four pairs of organic compounds.
Table 3.1
[Table_1]
(i) Complete Table 3.1 to:
• identify a reagent which can distinguish between the compounds in each pair
• give the positive result of the chemical test and identify which compound shows this result.
Use a different reagent for each test. [8]
(ii) $\textbf{A1}$ and $\textbf{A2}$ are structural isomers.
Define structural isomers. [1]
(iii) Give the systematic name of $\textbf{B2}$. [1]
(iv) Deduce the molecular formula of $\textbf{D1}$. [1]
(b) $\textbf{D2}$ forms polymer $\textbf{Z}$ when heated gently.
(i) Identify the type of polymer that forms from $\textbf{D2}$. [1]
(ii) Draw one repeat unit of polymer $\textbf{Z}$. [2]
(c) Organic compound $\textbf{E}$ contains three carbon atoms. $\textbf{E}$ reacts with cold dilute acidified $\text{KMnO}_4(aq)$ to form a single compound $\textbf{F}$ with $M_r = 154.9$.
Fig. 3.1 shows the infrared spectrum of $\textbf{E}$.
Fig. 3.2 shows the infrared spectrum of $\textbf{F}$.
Table 3.2
[Table_2]
(i) Use the two infrared spectra and Table 3.2 to identify the functional group present only in $\textbf{E}$.
Explain your answer, referring only to absorptions at frequencies greater than $1500 \text{cm}^{-1}$. [1]
(ii) Use the infrared spectrum of $\textbf{F}$ to identify the functional group formed when $\textbf{E}$ reacts with cold dilute acidified $\text{KMnO}_4(aq)$.
Explain your answer, referring only to absorptions at frequencies greater than $1500 \text{cm}^{-1}$. [1]
(iii) The mass spectrum of $\textbf{E}$ shows a molecular ion peak and an \(\text{M}+2\) peak of approximately equal abundance at \(m/e = 120\) and \(122\). Deduce the relative molecular mass, $M_r$, of $\textbf{E}$. [1]
(iv) Use the information in 3(c) to suggest a structure for $\textbf{E}$. [1]
(v) Complete the equation for the reaction of $\textbf{E}$ with cold dilute acidified $\text{KMnO}_4(aq)$ to form $\textbf{F}$. In the equation, $[O]$ represents cold dilute acidified $\text{KMnO}_4(aq)$.
$\text{H}_2\text{O} + [O] + \text{.....................} \rightarrow \text{...............................}$ [1]
(d) $\textbf{C2}$ can be synthesised using $\textbf{A1}$ as a single organic reactant.
Devise a multi-step synthetic route to form $\textbf{C2}$ from $\textbf{A1}$. Identify relevant reagents and conditions, and state the organic products of each step. [3]
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