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(a) (i) Explain the lack of reactivity of nitrogen gas, $N_2(g)$.
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(ii) Covalent bonds can be $\sigma$ bonds or $\pi$ bonds.
Complete Table 1.1 to show the number of $\sigma$ and $\pi$ bonds in a molecule of $N_2$ and to describe how the orbitals overlap to form $\sigma$ and $\pi$ bonds.
\[ \text{Table 1.1} \]
\[ \begin{array}{|c|c|c|} \hline \text{} & \sigma \text{ bond} & \pi \text{ bond} \\ \hline \text{number of bonds in } N_2 & & \\ \hline \text{how the orbitals overlap} & & \\ \hline \end{array} \]
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(b) (i) A sample of $Al$ reacts with an excess of $Cl_2$.
State the oxidation number of $Al$ in the product of the reaction.
oxidation number of $Al$ .............................................. [1]
(ii) State what determines the maximum oxidation number of the Period 3 elements in their oxides.
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(c) Separate samples of aluminium oxide, $Al_2O_3$, and phosphorus(V) oxide, $P_4O_{10}$, react with an excess of $NaOH(aq)$ at room temperature.
(i) Give the state of $Al_2O_3$ and $P_4O_{10}$ at room temperature.
$Al_2O_3$ ...........................................................
$P_4O_{10}$ ............................................................. [1]
(ii) Write an equation for the reaction of each oxide with an excess of $NaOH(aq)$ at room temperature.
$Al_2O_3$ + ................................................................................
$P_4O_{10}$ + ............................................................................. [2]
(d) The oxide of silicon reacts with calcium oxide in an addition reaction to produce calcium silicate, $CaSiO_3$. The oxidation number of calcium in $CaSiO_3$ is +II.
(i) Deduce the oxidation number of silicon in calcium silicate.
oxidation number of silicon ......................................... [1]
(ii) Calcium oxide can be made from calcium carbonate in a single-step reaction.
Identify the type of reaction that occurs.
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(a) Describe and explain the change, if any, to the percentage yield of NH$_3$(g) produced in B compared to A.
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(b) (i) Describe and explain the change, if any, to the percentage yield of NH$_3$(g) produced in C compared to A.
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(ii) Describe and explain the change to the rate of the forward reaction that occurs to establish the equilibrium in C compared to A.
You do not need to refer to the Boltzmann distribution in your answer.
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(c) (i) Write an expression for the equilibrium constant, K$_p$, for reaction 1. State the units.
K$_p$ =
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(ii) Equilibrium mixture D is made when 1.0 mol of N$_2$(g) and 3.0 mol of H$_2$(g) are added to a sealed container at 750°C and 1000 atm and left to reach equilibrium. This mixture contains 1.16 mol of NH$_3$(g).
Calculate the mole fraction of NH$_3$(g) in D.
mole fraction of NH$_3$(g) = ..............................[2]
(iii) The mole fraction of N$_2$(g) is 0.625 in a new equilibrium mixture, E.
Calculate the partial pressure of N$_2$(g) in E when the total pressure is 1000 atm.
partial pressure of N$_2$(g) = .............................. atm [1]
(d) When oxides of nitrogen escape into the atmosphere they may be involved in:
• formation of acid rain from sulfur dioxide
• formation of photochemical smog.
(i) Identify the role of NO and NO$_2$ in the formation of H$_2$SO$_4$ from SO$_2$ in the atmosphere to produce acid rain.
Use relevant equations to support your answer.
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(ii) Outline how NO and NO$_2$ may contribute to the formation of photochemical smog.
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(a) Write an equation to show the reaction for the standard enthalpy change of formation of $\text{H}_2\text{O}$. Include state symbols.
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(b) Water is one of the products in the reaction of $\text{B}_2\text{O}_3$ and $\text{NH}_3$, as shown in reaction 2.
reaction 2 $\text{B}_2\text{O}_3 + 2\text{NH}_3 \rightarrow 2\text{BN} + 3\text{H}_2\text{O}$
Table 3.1 shows information about the standard enthalpy change of formation, $\Delta H_f^{\ominus}$, of some substances.
[Table_1]
Calculate the enthalpy change, $\Delta H$, for reaction 2 using the data from Table 3.1.
$\Delta H = \text{........................................................} \text{kJ mol}^{-1}$ [2]
(c) Boron carbide is a hard crystalline solid that has a melting point greater than 2000 °C.
(i) Suggest the structure and bonding in boron carbide.
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(ii) 100 g of pure boron carbide contains 78.26 g of boron.
Calculate the empirical formula of boron carbide.
Show your working.
empirical formula of boron carbide ........................... [2]
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(a) \( NH_3(g) \) reacts with \( HCl(g) \) to produce \( NH_4Cl(s) \), as shown.
\[ NH_3(g) + HCl(g) \rightarrow NH_4Cl(s) \]
Draw a diagram to show the ionic, covalent and coordinate bonding present in a formula unit of \( NH_4Cl \).
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(b) An exothermic reaction occurs when \( NH_4^+(aq) \) is added to \( OH^-(aq) \).
(i) Identify the type of reaction.
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(ii) Construct an ionic equation for the reaction of \( NH_4^+ \) and \( OH^- \).
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(c) Substitution reactions of \( NH_3 \) and \( OH^- \) with halogenoalkanes both involve a lone pair of electrons.
(i) Name the role of \( NH_3 \) and \( OH^- \) in these reactions.
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(ii) Suggest which species, \( NH_3 \) or \( OH^- \), is more reactive during these reactions. Explain your answer.
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(d) When 2-bromo-2-methylpropane reacts with \( OH^- \), two mechanisms, \( S_N1 \) and \( S_N2 \), both occur. The \( S_N2 \) mechanism has a slower rate.
Fig. 4.1 shows the reaction pathway diagram for the \( S_N1 \) mechanism.
Sketch a graph on Fig. 4.1 to show the reaction pathway for the \( S_N2 \) mechanism. [2]
[Image_Fig_4.1]
(e) (i) Complete Fig. 4.2 to show the mechanism for the \( S_N1 \) reaction that occurs when \( CH_3CHBrC_2H_5 \) reacts with \( NH_3 \) to produce \( CH_3CH(NH_2)C_2H_5 \). Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate.
[Image_Fig_4.2] [3]
(ii) Identify the inorganic product that forms in the reaction in Fig. 4.2.
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(iii) Give the systematic name for the organic product \( CH_3CH(NH_2)C_2H_5 \).
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(f) (i) Complete Table 4.1 by drawing the structural formula of the intermediate that is formed when 2-bromo-2-methylpropane reacts in an \( S_N1 \) reaction.
[Table_Table_4.1] [1]
(ii) Identify the halogenoalkane in Table 4.1 that has the greater tendency to react using the \( S_N1 \) mechanism. Explain your answer.
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(a) M reacts to form R by the addition of one reagent, as shown in Fig. 5.1.
Identify the reagent and conditions for this reaction.
(b) R is also made from M by two steps, as shown in Fig. 5.2.
(i) Identify the reagents and conditions for steps 1 and 2 in Fig. 5.2.
step 1 ................................................................................................................................................
step 2 ................................................................................................................................................
(ii) Name the mechanism for step 1 in Fig. 5.2.
(c) The infrared spectrum of R is shown in Fig. 5.3.
Use the absorptions in the region above $1500 \text{cm}^{-1}$ in Table 5.1 when answering this question.
• Add F to Fig. 5.3 to identify the peak that is present in an infrared spectrum of both Q and R. Identify the bond that corresponds to the absorption for F.
• Add G to Fig. 5.3 to identify the peak that is not present in an infrared spectrum of Q. Identify the bond that corresponds to the absorption for G.
(d) Y is made from Q in a three-step reaction.
(i) Draw the structure of W in the box in Fig. 5.4.
(ii) In step 2, W is heated with HCl(aq) to produce X and an inorganic product.
Identify the formula of the inorganic product.
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(iii) In step 3, X reacts with reducing agent Z to produce Y.
Complete the equation for the reaction of X with Z.
Use a molecular formula to represent the organic product.
Use [H] to represent one atom of hydrogen from Z.
…… $C_8H_{12}O_4$ + ……[H] $\rightarrow$ ..............................................................................................................
(iv) Identify Z.
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