A Level Chemistry 9701 Paper 23, May/June 2024

Explain the lack of reactivity of nitrogen gas, ${\mathrm{N}}_2(\mathrm{g})$.

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 ${\mathrm{N}}_2$ and to describe how the orbitals overlap to form $\sigma$ and $\pi$ bonds. Table 1.1

A sample of $\mathrm{A}\mathrm{l}$ reacts with an excess of $\mathrm{C}{\mathrm{l}}_2$. State the oxidation number of $\mathrm{A}\mathrm{l}$ in the product of the reaction. oxidation number of $\mathrm{A}\mathrm{l}$ ................................................................................................

State what determines the maximum oxidation number of the Period 3 elements in their oxides.

Separate samples of aluminium oxide, $\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$, and phosphorus(V) oxide, ${\mathrm{P}}_4{\mathrm{O}}_{10}$, react with an excess of $\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}(\mathrm{a}\mathrm{q})$ at room temperature. Give the state of $\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ and ${\mathrm{P}}_4{\mathrm{O}}_{10}$ at room temperature. $\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ ................................................................................................................................. ${\mathrm{P}}_4{\mathrm{O}}_{10}$ .................................................................................................................................

Write an equation for the reaction of each oxide with an excess of $\mathrm{N}\mathrm{a}\mathrm{O}\mathrm{H}(\mathrm{a}\mathrm{q})$ at room temperature. $\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3+$ ............................................................................................................................ ${\mathrm{P}}_4{\mathrm{O}}_{10}+$ ...........................................................................................................................

The oxide of silicon reacts with calcium oxide in an addition reaction to produce calcium silicate, $\mathrm{C}\mathrm{a}\mathrm{S}\mathrm{i}{\mathrm{O}}_3$. The oxidation number of calcium in $\mathrm{C}\mathrm{a}\mathrm{S}\mathrm{i}{\mathrm{O}}_3$ is +II. Deduce the oxidation number of silicon in calcium silicate. oxidation number of silicon ..........................................................................................

Calcium oxide can be made from calcium carbonate in a single-step reaction. Identify the type of reaction that occurs.

Describe and explain the change, if any, to the percentage yield of $\mathrm{N}{\mathrm{H}}_3(\mathrm{g})$ produced in B compared to A.

Describe and explain the change, if any, to the percentage yield of $\mathrm{N}{\mathrm{H}}_3(\mathrm{g})$ produced in C compared to A.

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.

Write an expression for the equilibrium constant, $K_{\mathrm{p}}$, for reaction 1. State the units. $K_{\mathrm{p}}=$ units ..............................

Equilibrium mixture D is made when $1.0\text{ mol}$ of ${\mathrm{N}}_2(\mathrm{g})$ and $3.0\text{ mol}$ of ${\mathrm{H}}_2(\mathrm{g})$ are added to a sealed container at $750{}^{\circ }\mathrm{C}$ and $1000\text{ atm}$ and left to reach equilibrium. This mixture contains $1.16\text{ mol}$ of $\mathrm{N}{\mathrm{H}}_3(\mathrm{g})$. Calculate the mole fraction of $\mathrm{N}{\mathrm{H}}_3(\mathrm{g})$ in D. mole fraction of $\mathrm{N}{\mathrm{H}}_3(\mathrm{g})=$ ..............................

The mole fraction of ${\mathrm{N}}_2(\mathrm{g})$ is 0.625 in a new equilibrium mixture, E. Calculate the partial pressure of ${\mathrm{N}}_2(\mathrm{g})$ in E when the total pressure is $1000\text{ atm}$. partial pressure of ${\mathrm{N}}_2(\mathrm{g})=$ .............................. atm

When oxides of nitrogen escape into the atmosphere they may be involved in: • formation of acid rain from sulfur dioxide • formation of photochemical smog. Identify the role of $\mathrm{N}\mathrm{O}$ and $\mathrm{N}{\mathrm{O}}_2$ in the formation of ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ from $\mathrm{S}{\mathrm{O}}_2$ in the atmosphere to produce acid rain. Use relevant equations to support your answer.

Outline how $\mathrm{N}\mathrm{O}$ and $\mathrm{N}{\mathrm{O}}_2$ may contribute to the formation of photochemical smog.

Write an equation to show the reaction for the standard enthalpy change of formation of ${\mathrm{H}}_2\mathrm{O}$. Include state symbols.

Water is one of the products in the reaction of ${\mathrm{B}}_2{\mathrm{O}}_3$ and $\mathrm{N}{\mathrm{H}}_3$, as shown in reaction 2. reaction 2 ${\mathrm{B}}_2{\mathrm{O}}_3+2\mathrm{N}{\mathrm{H}}_3\to 2\mathrm{B}\mathrm{N}+3{\mathrm{H}}_2\mathrm{O}$ Table 3.1 shows information about the standard enthalpy change of formation, $\mathrm{\Delta }{H}_{\mathrm{f}}^{\ominus }$, of some substances. Table 3.1

Calculate the enthalpy change, $\mathrm{\Delta }H$, for reaction 2 using the data from Table 3.1. $\mathrm{\Delta }H=$ .............................. ${\text{kJ}\text{mol}}^{-1}$

Boron carbide is a hard crystalline solid that has a melting point greater than $2000{}^{\circ }\mathrm{C}$. Suggest the structure and bonding in boron carbide.

$100\text{ g}$ of pure boron carbide contains $78.26\text{ g}$ of boron. Calculate the empirical formula of boron carbide. Show your working. empirical formula of boron carbide ..............................

$\mathrm{N}{\mathrm{H}}_3(\mathrm{g})$ reacts with $\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{g})$ to produce $\mathrm{N}{\mathrm{H}}_4\mathrm{C}\mathrm{l}(\mathrm{s})$, as shown. $$\mathrm{N}{\mathrm{H}}_3(\mathrm{g})+\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{g})\to \mathrm{N}{\mathrm{H}}_4\mathrm{C}\mathrm{l}(\mathrm{s})$$ Draw a diagram to show the ionic, covalent and coordinate bonding present in a formula unit of $\mathrm{N}{\mathrm{H}}_4\mathrm{C}\mathrm{l}$.

An exothermic reaction occurs when $\mathrm{N}{\mathrm{H}}_4^{+}(\mathrm{a}\mathrm{q})$ is added to $\mathrm{O}{\mathrm{H}}^{-}(\mathrm{a}\mathrm{q})$. Identify the type of reaction.

Construct an ionic equation for the reaction of $\mathrm{N}{\mathrm{H}}_4^{+}$ and $\mathrm{O}{\mathrm{H}}^{-}$.

Substitution reactions of $\mathrm{N}{\mathrm{H}}_3$ and $\mathrm{O}{\mathrm{H}}^{-}$ with halogenoalkanes both involve a lone pair of electrons. Name the role of $\mathrm{N}{\mathrm{H}}_3$ and $\mathrm{O}{\mathrm{H}}^{-}$ in these reactions.

Suggest which species, $\mathrm{N}{\mathrm{H}}_3$ or $\mathrm{O}{\mathrm{H}}^{-}$, is more reactive during these reactions. Explain your answer.

When 2-bromo-2-methylpropane reacts with $\mathrm{O}{\mathrm{H}}^{-}$, two mechanisms, ${\mathrm{S}}_{\mathrm{N}}1$ and ${\mathrm{S}}_{\mathrm{N}}2$, both occur. The ${\mathrm{S}}_{\mathrm{N}}2$ mechanism has a slower rate. Fig. 4.1 shows the reaction pathway diagram for the ${\mathrm{S}}_{\mathrm{N}}1$ mechanism. Sketch a graph on Fig. 4.1 to show the reaction pathway for the ${\mathrm{S}}_{\mathrm{N}}2$ mechanism.

Complete Fig. 4.2 to show the mechanism for the ${\mathrm{S}}_{\mathrm{N}}1$ reaction that occurs when $\mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{H}\mathrm{B}\mathrm{r}{\mathrm{C}}_2{\mathrm{H}}_5$ reacts with $\mathrm{N}{\mathrm{H}}_3$ to produce $\mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{H}(\mathrm{N}{\mathrm{H}}_2){\mathrm{C}}_2{\mathrm{H}}_5$. Include charges, dipoles, lone pairs of electrons and curly arrows, as appropriate.

Identify the inorganic product that forms in the reaction in Fig. 4.2.

Give the systematic name for the organic product $\mathrm{C}{\mathrm{H}}_3\mathrm{C}\mathrm{H}(\mathrm{N}{\mathrm{H}}_2){\mathrm{C}}_2{\mathrm{H}}_5$.

Complete Table 4.1 by drawing the structural formula of the intermediate that is formed when 2-bromo-2-methylpropane reacts in an ${\mathrm{S}}_{\mathrm{N}}1$ reaction. Table 4.1

Identify the halogenoalkane in Table 4.1 that has the greater tendency to react using the ${\mathrm{S}}_{\mathrm{N}}1$ mechanism. Explain your answer.

M reacts to form R by the addition of one reagent, as shown in Fig. 5.1. Fig. 5.1 Identify the reagent and conditions for this reaction.

R is also made from M by two steps, as shown in Fig. 5.2. Fig. 5.2 Identify the reagents and conditions for steps 1 and 2 in Fig. 5.2. step 1 ................................................................................................................................ step 2 ................................................................................................................................

Name the mechanism for step 1 in Fig. 5.2.

The infrared spectrum of R is shown in Fig. 5.3. Fig. 5.3 Table 5.1

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. ...........................................................................................................................................

Y is made from Q in a three-step reaction. Fig. 5.4 Draw the structure of W in the box in Fig. 5.4.

In step 2, W is heated with $\mathrm{H}\mathrm{C}\mathrm{l}(\mathrm{a}\mathrm{q})$ to produce X and an inorganic product. Identify the formula of the inorganic product.

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. ...... ${\mathrm{C}}_8{\mathrm{H}}_{12}{\mathrm{O}}_4+$ ......[H] $\to$ .........................................................................................

Identify Z.