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How many stereoisomers exist for the organic compound 4-methylhex-2-ene?

A buffer solution is prepared by mixing \(50.0\text{ cm}^3\) of \(0.100\text{ mol dm}^{-3}\) propanoic acid (\(K_a = 1.35 \times 10^{-5}\text{ mol dm}^{-3}\)) and \(25.0\text{ cm}^3\) of \(0.120\text{ mol dm}^{-3}\) sodium propanoate. What is the pH of this buffer solution?

For the reaction \(2A + B + C \rightarrow D\), the following initial rates were measured at different starting concentrations: Experiment 1: \([A] = 0.10\text{ mol dm}^{-3}\), \([B] = 0.10\text{ mol dm}^{-3}\), \([C] = 0.10\text{ mol dm}^{-3}\), Initial Rate = \(1.2 \times 10^{-3}\text{ mol dm}^{-3}\text{ s}^{-1}\); Experiment 2: \([A] = 0.20\text{ mol dm}^{-3}\), \([B] = 0.10\text{ mol dm}^{-3}\), \([C] = 0.10\text{ mol dm}^{-3}\), Initial Rate = \(2.4 \times 10^{-3}\text{ mol dm}^{-3}\text{ s}^{-1}\); Experiment 3: \([A] = 0.10\text{ mol dm}^{-3}\), \([B] = 0.20\text{ mol dm}^{-3}\), \([C] = 0.10\text{ mol dm}^{-3}\), Initial Rate = \(4.8 \times 10^{-3}\text{ mol dm}^{-3}\text{ s}^{-1}\); Experiment 4: \([A] = 0.10\text{ mol dm}^{-3}\), \([B] = 0.10\text{ mol dm}^{-3}\), \([C] = 0.20\text{ mol dm}^{-3}\), Initial Rate = \(1.2 \times 10^{-3}\text{ mol dm}^{-3}\text{ s}^{-1}\). What is the unit of the rate constant, \(k\)?

Calculate the standard enthalpy of formation of liquid hydrazine, \(N_2H_4(l)\), given the following standard enthalpy of combustion data: \(\Delta H_c^\theta[H_2(g)] = -286\text{ kJ mol}^{-1}\), \(\Delta H_c^\theta[N_2H_4(l)] = -622\text{ kJ mol}^{-1}\).

Which set of reagents and reaction conditions is required to synthesize 4-hydroxyazobenzene starting from phenylamine?

Which statement correctly describes and explains a trend in the melting points of the elements across Period 3 (from sodium to argon)?

A \(10\text{ cm}^3\) sample of a gaseous hydrocarbon, X, is completely combusted in \(80\text{ cm}^3\) of oxygen (an excess). After cooling to room temperature, the remaining gas volume is \(65\text{ cm}^3\). When this gas mixture is passed through aqueous sodium hydroxide, the volume decreases to \(25\text{ cm}^3\). What is the molecular formula of hydrocarbon X?

Using the standard electrode potentials below, which species can be oxidised by aqueous bromine, \(Br_2(aq)\), under standard conditions, but cannot be oxidised by aqueous iodine, \(I_2(aq)\)? \(I_2(aq) + 2e^- \rightleftharpoons 2I^-(aq) \quad E^\theta = +0.54\text{ V}\); \(Fe^{3+}(aq) + e^- \rightleftharpoons Fe^{2+}(aq) \quad E^\theta = +0.77\text{ V}\); \(Br_2(aq) + 2e^- \rightleftharpoons 2Br^-(aq) \quad E^\theta = +1.07\text{ V}\).

A mixture containing 1.50 g of magnesium carbonate and 1.50 g of calcium carbonate is heated strongly until no further change occurs and both carbonates are completely decomposed. What is the total volume of carbon dioxide gas, in \(cm^3\), released when measured at room temperature and pressure (r.t.p.)? [Take the molar volume of a gas at r.t.p. as 24.0 \(dm^3\) \(mol^{-1}\); Ar: Mg = 24.3, Ca = 40.1, C = 12.0, O = 16.0]

How many stereoisomers exist for the organic compound 4-chlorohex-2-ene?

The gas-phase reaction \(\text{PCl}_5\text{(g)} \rightleftharpoons \text{PCl}_3\text{(g)} + \text{Cl}_2\text{(g)}\) is allowed to reach equilibrium in a closed vessel at a constant temperature T. At equilibrium, the total pressure is \(2.00 \times 10^5\text{ Pa}\) and the mole fraction of \(\text{Cl}_2\) is 0.30. What is the value of the equilibrium constant \(K_p\) at this temperature?

The kinetics of the reaction \(2\text{NO(g)} + 2\text{H}_2\text{(g)} \rightarrow \text{N}_2\text{(g)} + 2\text{H}_2\text{O(g)}\) was investigated at a constant temperature, and the following initial rate data was obtained. Expt 1: \([\text{NO}] = 0.10\text{ mol dm}^{-3}\), \([\text{H}_2] = 0.10\text{ mol dm}^{-3}\), Initial rate = \(1.20 \times 10^{-3}\text{ mol dm}^{-3}\text{ s}^{-1}\). Expt 2: \([\text{NO}] = 0.20\text{ mol dm}^{-3}\), \([\text{H}_2] = 0.10\text{ mol dm}^{-3}\), Initial rate = \(4.80 \times 10^{-3}\text{ mol dm}^{-3}\text{ s}^{-1}\). Expt 3: \([\text{NO}] = 0.10\text{ mol dm}^{-3}\), \([\text{H}_2] = 0.20\text{ mol dm}^{-3}\), Initial rate = \(2.40 \times 10^{-3}\text{ mol dm}^{-3}\text{ s}^{-1}\). What is the value and units of the rate constant, k, for this reaction?

The standard enthalpy change of combustion of liquid hydrazine, \(\text{N}_2\text{H}_4\text{(l)}\), is \(-622\text{ kJ mol}^{-1}\), forming nitrogen gas and liquid water. The standard enthalpy change of formation of liquid water is \(-286\text{ kJ mol}^{-1}\). What is the standard enthalpy change of formation of liquid hydrazine?

In the synthesis of an azo dye, phenylamine is first converted to the benzenediazonium ion in Step 1, which is then coupled with phenol in Step 2. Which set of reagents and conditions is correct for these two steps?

Which of the following lists the species \(\text{Na}^+\), \(\text{Mg}^{2+}\), \(\text{P}^{3-}\), and \(\text{S}^{2-}\) in order of decreasing ionic radius?

Using the standard electrode potential values provided, which reaction is thermodynamically feasible under standard conditions? \(\text{Fe}^{3+}\text{(aq)} + \text{e}^- \rightleftharpoons \text{Fe}^{2+}\text{(aq)} \quad (E^\theta = +0.77\text{ V})\); \(\text{I}_2\text{(aq)} + 2\text{e}^- \rightleftharpoons 2\text{I}^-\text{(aq)} \quad (E^\theta = +0.54\text{ V})\); \(\text{Br}_2\text{(aq)} + 2\text{e}^- \rightleftharpoons 2\text{Br}^-\text{(aq)} \quad (E^\theta = +1.07\text{ V})\); \(\text{S}_4\text{O}_6^{2-}\text{(aq)} + 2\text{e}^- \rightleftharpoons 2\text{S}_2\text{O}_3^{2-}\text{(aq)} \quad (E^\theta = +0.09\text{ V})\)

A sample of a bioactive peptide is hydrolysed to yield an amino acid with the molecular formula \(\text{C}_4\text{H}_9\text{NO}_3\). This amino acid has the IUPAC name 2-amino-3-hydroxybutanoic acid. How many chiral centres are present in one molecule of this amino acid?

How many stereoisomers exist for the compound 4-chlorohex-2-ene?

At 298 K, the solubility product, \(K_{sp}\), of calcium sulfate, \(\text{CaSO}_4\), is \(2.4 \times 10^{-5}\text{ mol}^2\text{dm}^{-6}\). A student mixes equal volumes of \(0.010\text{ mol dm}^{-3}\) \(\text{CaCl}_2\text{(aq)}\) and \(0.010\text{ mol dm}^{-3}\) \(\text{Na}_2\text{SO}_4\text{(aq)}\). What is the ionic product of \(\text{CaSO}_4\) in this mixture, and does a precipitate form?

At 298 K, the standard electrode potential for the copper half-cell is given by: \(\text{Cu}^{2+}(\text{aq}) + 2\text{e}^- \rightleftharpoons \text{Cu}(\text{s}) \quad E^\theta = +0.34\text{ V}\). Using the Nernst equation, \(E = E^\theta + \frac{0.059}{z} \log [\text{Cu}^{2+}(\text{aq})]\), what is the electrode potential, \(E\), of a copper electrode immersed in a \(1.0 \times 10^{-4}\text{ mol dm}^{-3}\) solution of \(\text{Cu}^{2+}(\text{aq})\)?

Using the average bond energies given below, what is the enthalpy change, \(\Delta H\), for the gas-phase reaction: \(\text{CH}_4(\text{g}) + \text{Cl}_2(\text{g}) \rightarrow \text{CH}_3\text{Cl}(\text{g}) + \text{HCl}(\text{g})\)? Bond energies: \(\text{C-H} = 410\text{ kJ mol}^{-1}\); \(\text{Cl-Cl} = 242\text{ kJ mol}^{-1}\); \(\text{C-Cl} = 340\text{ kJ mol}^{-1}\); \(\text{H-Cl} = 431\text{ kJ mol}^{-1}\).

Which of the following correctly ranks the four nitrogen-containing compounds in order of decreasing basic strength (most basic first)?

Which statement correctly explains the trend in electrical conductivity across the Period 3 metals (sodium, magnesium, and aluminium)?

An organic compound contains only carbon, hydrogen, and oxygen. Complete combustion of \(0.150\text{ g}\) of this compound produced \(0.220\text{ g}\) of \(\text{CO}_2\) and \(0.090\text{ g}\) of \(\text{H}_2\text{O}\). What is the empirical formula of this compound?

Four different halogenoalkanes are heated separately with aqueous silver nitrate in ethanol at 50 °C. Which halogenoalkane will produce a precipitate the fastest?

An organic compound has the following structural formula:

\(\text{CH}_3-\text{CH(OH)}-\text{CH}=\text{CH}-\text{CH(CH}_3)-\text{CH}_2-\text{CH}_3\)

How many stereoisomers exist for this compound?

A sample of pure gas A is placed in a sealed container at a constant temperature. It establishes the following equilibrium:

\[2\text{A(g)} \rightleftharpoons 2\text{B(g)} + \text{C(g)}\]

The initial partial pressure of A is \(1.00\text{ atm}\). At equilibrium, the total pressure in the container is found to be \(1.30\text{ atm}\).

What is the value of the equilibrium constant, \(K_p\), for this reaction?

The table below shows initial rate data for the reaction between reactants X, Y, and Z:

\[\text{X} + \text{Y} + \text{Z} \rightarrow \text{Products}\]

| Run | \([\text{X}] / \text{mol dm}^{-3}\) | \([\text{Y}] / \text{mol dm}^{-3}\) | \([\text{Z}] / \text{mol dm}^{-3}\) | Initial Rate / \(10^{-3}\text{ mol dm}^{-3}\text{ s}^{-1}\) |
|---|---|---|---|---|
| 1 | 0.10 | 0.10 | 0.10 | 1.2 |
| 2 | 0.20 | 0.10 | 0.10 | 2.4 |
| 3 | 0.10 | 0.20 | 0.10 | 4.8 |
| 4 | 0.10 | 0.10 | 0.20 | 1.2 |

What is the value and correct unit of the rate constant, \(k\), for this reaction?

The dry reforming of methane is represented by the following chemical equation:

\[\text{CH}_4\text{(g)} + \text{CO}_2\text{(g)} \rightarrow 2\text{CO(g)} + 2\text{H}_2\text{(g)}\]

Using the standard enthalpies of combustion, \(\Delta H^\ominus_c\), given below, what is the standard enthalpy change of this reaction, \(\Delta H^\ominus_r\)?

- \(\Delta H^\ominus_c [\text{CH}_4\text{(g)}] = -890\text{ kJ mol}^{-1}\)
- \(\Delta H^\ominus_c [\text{CO(g)}] = -283\text{ kJ mol}^{-1}\)
- \(\Delta H^\ominus_c [\text{H}_2\text{(g)}] = -286\text{ kJ mol}^{-1}\)

Which option lists the following nitrogen-containing compounds in order of increasing pH of their \(0.10\text{ mol dm}^{-3}\) aqueous solutions?

- Ammonia, \(\text{NH}_3\)
- Diethylamine, \((\text{CH}_3\text{CH}_2)_2\text{NH}\)
- Ethylamine, \(\text{CH}_3\text{CH}_2\text{NH}_2\)
- Phenylamine, \(\text{C}_6\text{H}_5\text{NH}_2\)

Equal amounts (in moles) of four Period 3 chlorides are separately added to equal volumes of water.

Which chloride produces the solution with the lowest pH?

A \(10\text{ cm}^3\) sample of a gaseous hydrocarbon, \(\text{C}_x\text{H}_y\), was reacted with \(80\text{ cm}^3\) of oxygen (an excess).

After complete combustion and cooling to room temperature and pressure, the remaining gas volume was \(60\text{ cm}^3\). When this remaining gas was passed through aqueous sodium hydroxide, the volume decreased to \(30\text{ cm}^3\).

What is the molecular formula of the hydrocarbon?

When excess aqueous ammonia is added to aqueous copper(II) sulfate, the light blue precipitate initially formed dissolves to give a deep blue solution containing the complex ion \([\text{Cu}(\text{NH}_3)_4(\text{H}_2\text{O})_2]^{2+}\).

Which statement correctly explains the shift in light absorption that occurs when the coordinated water ligands are replaced by ammonia ligands?

A student carries out an experiment to determine the formula of a hydrated magnesium carbonate, \(\text{MgCO}_3 \cdot n\text{H}_2\text{O}\).

A \(4.149\text{ g}\) sample of \(\text{MgCO}_3 \cdot n\text{H}_2\text{O}\) is heated gently in a crucible to drive off all the water of crystallisation. The mass of the anhydrous residue, \(\text{MgCO}_3\), is \(2.529\text{ g}\).

(a) Define the term *relative formula mass*. [1]

(b) (i) Calculate the value of \(n\) in \(\text{MgCO}_3 \cdot n\text{H}_2\text{O}\). Show your working. [3]

(ii) Write an equation, including state symbols, for the thermal decomposition of anhydrous magnesium carbonate. [2]

(iii) Calculate the volume, in \(\text{cm}^3\), of carbon dioxide gas produced when the \(2.529\text{ g}\) of anhydrous magnesium carbonate is completely decomposed. Assume \(1\text{ mol}\) of gas occupies \(24.0\text{ dm}^3\) under these conditions. [2]

(c) (i) State and explain the trend in the thermal stability of the Group 2 carbonates down the group. [3]

(ii) State how the thermal stability of calcium nitrate compares to that of magnesium nitrate. [1]

The molecular formula \(\text{C}_3\text{H}_5\text{Cl}\) represents several structural and stereoisomers.

(a) Draw the skeletal structures of three acyclic (no rings) structural isomers with the formula \(\text{C}_3\text{H}_5\text{Cl}\). [3]

(b) One of these structural isomers exhibits stereoisomerism.

(i) Identify this isomer by its IUPAC name. [1]

(ii) Name and explain the type of stereoisomerism shown by this isomer. [3]

(iii) Draw the stereochemical structures of the two stereoisomers of this compound and label them clearly. [2]

(c) Another structural isomer of \(\text{C}_3\text{H}_5\text{Cl}\), 3-chloroprop-1-ene, reacts with cold dilute acidified potassium manganate(VII).

(i) Describe the observation for this reaction. [1]

(ii) Draw the structure of the organic product of this reaction. [2]

The standard enthalpy change of formation of liquid propan-1-ol, \(\text{C}_3\text{H}_7\text{OH(l)}\), can be calculated using standard enthalpy changes of combustion.

Standard enthalpy changes of combustion, \(\Delta H_{\text{c}}^\ominus\):
- \(\Delta H_{\text{c}}^\ominus[\text{C(s)}] = -393.5\text{ kJ mol}^{-1}\)
- \(\Delta H_{\text{c}}^\ominus[\text{H}_2\text{(g)}] = -285.8\text{ kJ mol}^{-1}\)
- \(\Delta H_{\text{c}}^\ominus[\text{C}_3\text{H}_7\text{OH(l)}] = -2021.0\text{ kJ mol}^{-1}\)

(a) Define *standard enthalpy change of combustion*. [2]

(b) (i) Write the chemical equation, including state symbols, for the reaction representing the standard enthalpy change of formation of liquid propan-1-ol, \(\text{C}_3\text{H}_7\text{OH}\). [2]

(ii) Draw a Hess's law cycle showing the relationship between the standard enthalpy change of formation of propan-1-ol and the standard enthalpy changes of combustion of carbon, hydrogen, and propan-1-ol. [2]

(iii) Calculate the standard enthalpy change of formation of liquid propan-1-ol, \(\Delta H_{\text{f}}^\ominus\). [2]

(c) The enthalpy change of combustion of propan-1-ol can be determined experimentally using a simple calorimeter. In an experiment, \(0.820\text{ g}\) of propan-1-ol is burned to heat \(150.0\text{ g}\) of water. The temperature of the water increases by \(28.4\ ^\circ\text{C}\).
(Specific heat capacity of water = \(4.18\text{ J g}^{-1}\ ^\circ\text{C}^{-1}\); \(M_{\text{r}}\) of propan-1-ol = \(60.0\))

(i) Calculate the heat energy absorbed by the water, in \(\text{kJ}\). [1]

(ii) Calculate the experimental enthalpy change of combustion of propan-1-ol, in \(\text{kJ mol}^{-1}\). [2]

(iii) Suggest why this experimental value is significantly less exothermic than the standard value. [1]

The physical properties of the elements in Period 3 show periodic trends.

(a) The first ionisation energies of the elements in Period 3 show a general increase from sodium to argon.

(i) Explain this general increase in first ionisation energy across Period 3. [3]

(ii) Explain why the first ionisation energy of aluminium is lower than that of magnesium. [2]

(iii) Explain why the first ionisation energy of sulfur is lower than that of phosphorus. [2]

(b) The melting points of the elements in Period 3 vary significantly.

(i) Describe the differences in the structures and bonding of silicon and phosphorus. [3]

(ii) State and explain how the electrical conductivity of silicon compares to that of sodium. [2]

Halogenoalkanes undergo nucleophilic substitution reactions.

(a) The rate of hydrolysis of halogenoalkanes can be determined by reacting them with aqueous silver nitrate in ethanol.

(i) Write an ionic equation, including state symbols, for the reaction that forms a precipitate when 1-bromobutane is hydrolysed in the presence of silver nitrate. [1]

(ii) State the color of the precipitate formed in (a)(i). [1]

(iii) State and explain the relative rates of hydrolysis of 1-chlorobutane, 1-bromobutane, and 1-iodobutane. [3]

(b) 2-bromo-2-methylpropane undergoes hydrolysis via an \(S_{\text{N}}1\) mechanism.

(i) Write the mechanism for this reaction with aqueous hydroxide ions. Draw the structures of the organic reactant, intermediate, and product, and use curly arrows to show the movement of electron pairs. [4]

(ii) Draw the reaction pathway diagram for this \(S_{\text{N}}1\) reaction. Label the axes, the reactants, products, activation energy (\(E_{\text{a}}\)), and the enthalpy change of the reaction (\(\Delta H\)), assuming the reaction is exothermic. [3]

Section instructions: Carry out the practical experiments in the laboratory as detailed, recording all observations, data tables, and subsequent quantitative analysis.

In this experiment, you will determine the relative molecular mass of a dibasic organic acid, \(H_2A\), by titrating its solution with standard sodium hydroxide solution.

FB 1 is a solution containing 4.50 g of the dibasic acid \(H_2A\) per \(dm^3\).
FB 2 is 0.100 \(mol\\,dm^{-3}\) sodium hydroxide, \(NaOH\).
Phenolphthalein is provided as an indicator.

(a) Pipette 25.0 \(cm^3\) of FB 1 into a conical flask. Titrate with FB 2 from the burette using phenolphthalein indicator until a permanent pale pink colour is obtained. Record your titration results in a suitable tabular format to find the average titre.

(b) Show your working to calculate the concentration of \(H_2A\) in \(mol\\,dm^{-3}\) and determine the relative molecular mass, \(M_r\), of \(H_2A\). (The reaction ratio is 1 mole of \(H_2A\) reacts with 2 moles of \(NaOH\).)

Section instructions: Carry out the practical experiments in the laboratory as detailed, recording all observations, data tables, and subsequent quantitative analysis.

In this experiment, you will determine the enthalpy change of solution of anhydrous sodium carbonate, \(Na_2CO_3\).

FB 3 is anhydrous sodium carbonate.
FB 4 is 2.00 \(mol\\,dm^{-3}\) hydrochloric acid, \(HCl\).

(a) Weigh a dry plastic cup. Record its mass. Add approximately 3.00 g of FB 3 into the cup and record the exact mass of the cup + FB 3.
(b) Using a measuring cylinder, transfer 50.0 \(cm^3\) of FB 4 into a second plastic cup. Measure and record its initial temperature every minute for 3 minutes. At the 4th minute, add the weighed FB 3, stir continuously, and record the temperature at minutes 5, 6, 7, 8, 9, and 10.
(c) Plot a graph of temperature against time, extrapolate to find the theoretical maximum temperature change (\(\Delta T\)).
(d) Calculate the heat energy change (\(q\)) and the molar enthalpy change of the reaction (\(\Delta H\)) in \(kJ\\,mol^{-1}\). (Assume specific heat capacity of the solution is 4.18 \(J\\,g^{-1}\\,K^{-1}\) and density is 1.00 \(g\\,cm^{-3}\).)

Section instructions: Carry out the practical experiments in the laboratory as detailed, recording all observations, data tables, and subsequent quantitative analysis.

In this experiment, you will identify the cations and anions present in two unknown solutions, FB 5 and FB 6, by performing qualitative analysis tests.

Perform the following tests on FB 5 and FB 6 and record your observations:

Test 1: Add aqueous sodium hydroxide dropwise, then in excess, to separate 2 \(cm^3\) portions of FB 5 and FB 6.
Test 2: Add aqueous ammonia dropwise, then in excess, to separate 2 \(cm^3\) portions of FB 5 and FB 6.
Test 3: Add acidified silver nitrate solution to separate 2 \(cm^3\) portions of FB 5 and FB 6.
Test 4: Add acidified barium chloride solution to separate 2 \(cm^3\) portions of FB 5 and FB 6.

Use your observations to identify the ions in FB 5 and FB 6.

The reaction between reactants X, Y, and Z was investigated at 298 K: 2X + Y + Z -> Products. The initial rates of reaction were measured under different concentration conditions: (1) [X] = 0.10, [Y] = 0.10, [Z] = 0.10 mol dm-3; Initial rate = 1.2 x 10^-3 mol dm-3 s-1. (2) [X] = 0.20, [Y] = 0.10, [Z] = 0.10 mol dm-3; Initial rate = 2.4 x 10^-3 mol dm-3 s-1. (3) [X] = 0.10, [Y] = 0.20, [Z] = 0.10 mol dm-3; Initial rate = 4.8 x 10^-3 mol dm-3 s-1. (4) [X] = 0.10, [Y] = 0.10, [Z] = 0.20 mol dm-3; Initial rate = 1.2 x 10^-3 mol dm-3 s-1. (a) Deduce the order of reaction with respect to X, Y, and Z, explaining your reasoning. (b) Write the rate equation for this reaction. (c) Calculate the rate constant, k, using the data from experiment 1, including its units. (d) State and explain how the rate constant, k, is affected by an increase in temperature, referencing activation energy and the Maxwell-Boltzmann distribution. (e) Propose a two-step mechanism for this reaction where the first step is the rate-determining step.

(a) Define the term optical isomers and explain the structural feature required for an organic compound to show optical isomerism. (b) 2-bromopropanoic acid, CH3CH(Br)COOH, is optically active. Draw three-dimensional structures of the two optical isomers. (c) The complex ion [Co(en)2Cl2]+ (where en is ethane-1,2-diamine) exhibits both geometrical and optical isomerism. (i) Draw the structures of the cis and trans geometrical isomers of [Co(en)2Cl2]+, using a simplified curve to represent the en ligand. (ii) State which geometrical isomer exhibits optical isomerism and draw 3D diagrams of its optical isomers.

An electrochemical cell consists of a Fe3+/Fe2+ half-cell and a Ag+/Ag half-cell. Standard electrode potentials: Fe3+(aq) + e- <=> Fe2+(aq) (E^o = +0.77 V) and Ag+(aq) + e- <=> Ag(s) (E^o = +0.80 V). (a) State which species is the anode, which is the cathode, and write the overall cell equation. (b) Calculate the standard cell potential. (c) The concentration of Ag+(aq) is reduced to 0.050 mol dm-3 while other species remain at 1.00 mol dm-3. (i) Use the Nernst equation E = E^o + (0.059/z)log[oxidised] to calculate the electrode potential of the silver half-cell. (ii) Calculate the new cell potential and state if the overall reaction is more or less thermodynamically feasible. (d) Describe the role and working of a salt bridge.

(a) Explain what is meant by a buffer solution. (b) A buffer is prepared by mixing 50.0 cm3 of 0.200 mol dm-3 propanoic acid (CH3CH2COOH) with 50.0 cm3 of 0.100 mol dm-3 NaOH. Ka of propanoic acid is 1.35 x 10^-5 mol dm-3. (i) Write the equation for the neutralization reaction. (ii) Calculate the concentrations of CH3CH2COOH and CH3CH2COO- in the buffer. (iii) Calculate the pH of the buffer. (c) Write chemical equations to show how this buffer controls pH when a small amount of strong acid is added.

(a) Describe the reaction pathway to synthesise phenylamine starting from benzene, including reagents, conditions, and the structure of the intermediate compound. (b) Phenylamine is converted into a diazonium salt, which is then coupled with phenol to form an azo dye. (i) State the reagents and conditions to convert phenylamine to benzenediazonium chloride. (ii) State the reagents, conditions, and draw the structure of the azo dye formed by coupling benzenediazonium chloride with phenol. (c) Compare the basicity of phenylamine and ethylamine, explaining your answer.

(a) Explain what is meant by a coordinate bond and why transition metals form them. (b)(i) Draw a dot-and-cross diagram of a water molecule showing all outer shell electrons. (ii) Describe the shape and bond angles of the [Cu(H2O)6]2+ complex ion. (c) When excess concentrated HCl is added to [Cu(H2O)6]2+, a yellow-green solution of [CuCl4]2- is formed. (i) Write the equation for this reaction. (ii) State the shape and bond angles of [CuCl4]2-. (d) Explain the origin of color in transition metal complexes.

(a) Define the term lattice energy of an ionic solid. (b) Use the following data to calculate the lattice energy of calcium oxide, CaO(s): Enthalpy of formation of CaO(s) = -635 kJ mol-1; Enthalpy of atomisation of Ca(s) = +178 kJ mol-1; First ionisation energy of Ca(g) = +590 kJ mol-1; Second ionisation energy of Ca(g) = +1145 kJ mol-1; Enthalpy of atomisation of O2(g) (0.5 * O-O bond enthalpy) = +249 kJ mol-1; First electron affinity of O(g) = -141 kJ mol-1; Second electron affinity of O(g) = +798 kJ mol-1. (c) Compare and explain the difference between the lattice energy of CaO and NaCl (-787 kJ mol-1). (d) Explain why the second electron affinity of oxygen is endothermic while the first is exothermic.

(a) Describe and explain the trend in electrical conductivity of the elements across Period 3 from sodium to silicon. (b) The first ionisation energies of Period 3 elements generally increase from left to right, but there are two notable drops. (i) Identify the two elements where these drops occur (compared to the preceding element). (ii) Explain the drop in first ionisation energy between magnesium and aluminium. (iii) Explain the drop in first ionisation energy between phosphorus and sulfur.

An electrochemical cell is set up to study the effect of concentration on electrode potential. (a) Define standard electrode potential, \(E^\theta\). [2 marks] (b) Describe the components and conditions required to set up the standard \(\text{Fe}^{3+}(\text{aq}) / \text{Fe}^{2+}(\text{aq})\) half-cell, and state the reference electrode it must be connected to in order to measure its standard electrode potential. [3 marks] (c) A student sets up an electrochemical cell consisting of a standard \(\text{Ag}^{+}(\text{aq}) / \text{Ag}(\text{s})\) half-cell (\(E^\theta = +0.80\text{ V}\)) and a non-standard \(\text{Fe}^{3+}(\text{aq}) / \text{Fe}^{2+}(\text{aq})\) half-cell. In the non-standard half-cell, \([\text{Fe}^{3+}] = 0.050\text{ mol dm}^{-3}\) and \([\text{Fe}^{2+}] = 0.85\text{ mol dm}^{-3}\) at \(298\text{ K}\). The standard electrode potential for the iron system is: \(\text{Fe}^{3+}(\text{aq}) + e^{-} \rightleftharpoons \text{Fe}^{2+}(\text{aq})\quad E^\theta = +0.77\text{ V}\). (i) Write the Nernst equation for the \(\text{Fe}^{3+}/\text{Fe}^{2+}\) half-cell. [1 mark] (ii) Calculate the electrode potential, \(E\), of this non-standard \(\text{Fe}^{3+}/\text{Fe}^{2+}\) half-cell at \(298\text{ K}\). Show your working. [2 marks] (iii) Calculate the cell potential, \(E_{\text{cell}}\), of the combined cell under these conditions and state the direction of electron flow in the external circuit. [1 mark] (d) Predict and explain the effect on the electrode potential of the \(\text{Fe}^{3+}/\text{Fe}^{2+}\) half-cell if sodium hydroxide solution is added to it, forming a precipitate of \(\text{Fe(OH)}_3\). [2 marks]

An experiment is carried out to find the formula of the complex formed between copper(II) ions, \(Cu^{2+}\), and a bidentate ligand, L, using the method of continuous variation. Solutions of \(Cu^{2+}(aq)\) and L(aq) are prepared, both having a concentration of \(0.100\text{ mol dm}^{-3}\). Varying volumes of these two solutions are mixed such that the total volume is always \(10.0\text{ cm}^3\). The absorbance of each mixture is measured using a colorimeter. The results are shown below:

- Mixture 1: \(V(Cu^{2+}) = 9.0\text{ cm}^3, V(L) = 1.0\text{ cm}^3\), Absorbance = 0.12
- Mixture 2: \(V(Cu^{2+}) = 8.0\text{ cm}^3, V(L) = 2.0\text{ cm}^3\), Absorbance = 0.24
- Mixture 3: \(V(Cu^{2+}) = 7.0\text{ cm}^3, V(L) = 3.0\text{ cm}^3\), Absorbance = 0.36
- Mixture 4: \(V(Cu^{2+}) = 6.0\text{ cm}^3, V(L) = 4.0\text{ cm}^3\), Absorbance = 0.48
- Mixture 5: \(V(Cu^{2+}) = 5.0\text{ cm}^3, V(L) = 5.0\text{ cm}^3\), Absorbance = 0.41
- Mixture 6: \(V(Cu^{2+}) = 4.0\text{ cm}^3, V(L) = 6.0\text{ cm}^3\), Absorbance = 0.72
- Mixture 7: \(V(Cu^{2+}) = 3.0\text{ cm}^3, V(L) = 7.0\text{ cm}^3\), Absorbance = 0.72
- Mixture 8: \(V(Cu^{2+}) = 2.0\text{ cm}^3, V(L) = 8.0\text{ cm}^3\), Absorbance = 0.48
- Mixture 9: \(V(Cu^{2+}) = 1.0\text{ cm}^3, V(L) = 9.0\text{ cm}^3\), Absorbance = 0.24

(a) Identify the independent variable and the dependent variable in this experiment. [2]

(b) Describe how a student would prepare 100 cm³ of the \(0.100\text{ mol dm}^{-3}\) solution of \(Cu^{2+}\) starting from solid copper(II) sulfate pentahydrate, \(CuSO_4 \cdot 5H_2O\). Show your working. [\(M_r = 249.6\)] [3]

(c) Analyze the experimental data:
(i) Identify which mixture has an anomalous absorbance value. Suggest a practical error that could account for this anomaly. [2]
(ii) Describe how the student should use a plotted graph of Absorbance (y-axis) against Volume of L (x-axis) to find the formula of the complex. [2]
(iii) The ideal lines of best fit are described by the equations:
\(A = 0.12 V_L\)
\(A = 2.40 - 0.24 V_L\)
Calculate the coordinates of the intersection point of these two lines, and determine the formula of the complex, \([CuL_n]^{2+}\). [3]

(d) Copper(II) ions in aqueous solution are pale blue, and the complex formed is deep purple-blue. Explain why a colorimeter is suitable for this experiment and state which color filter (or approximate wavelength of light) should be used. [2]

(e) Suggest one precaution the student must take when using a colorimeter to ensure that the measured absorbance values are reliable. [1]

A student wants to determine the partition coefficient, \(K_{pc}\), of ethanoic acid between water and butan-1-ol. The equation for the partition coefficient is:
\(K_{pc} = \frac{[CH_3COOH]_{organic}}{[CH_3COOH]_{aqueous}}\)

Procedure:
1. Mix \(50.0\text{ cm}^3\) of \(1.00\text{ mol dm}^{-3}\) aqueous ethanoic acid with \(50.0\text{ cm}^3\) of butan-1-ol in a separating funnel.
2. Shake the mixture thoroughly at intervals over 15 minutes, releasing pressure periodically.
3. Allow the mixture to stand until the two layers separate completely.
4. Run off the lower aqueous layer into a flask.
5. Pipette a \(10.00\text{ cm}^3\) sample of the aqueous layer into a conical flask and titrate against \(0.500\text{ mol dm}^{-3}\) aqueous sodium hydroxide, \(NaOH(aq)\), using phenolphthalein indicator.
6. Pipette a \(10.00\text{ cm}^3\) sample of the organic layer into a conical flask and titrate against \(0.500\text{ mol dm}^{-3}\) \(NaOH(aq)\).

Results:
- Titration of \(10.00\text{ cm}^3\) of the aqueous layer:
Initial burette reading = \(0.15\text{ cm}^3\); Final burette reading = \(14.45\text{ cm}^3\)
- Titration of \(10.00\text{ cm}^3\) of the organic layer:
Initial burette reading = \(1.20\text{ cm}^3\); Final burette reading = \(6.90\text{ cm}^3\)

(a) State why the separating funnel must be shaken thoroughly and then allowed to stand before separating the layers. [2]

(b) The density of water is \(1.00\text{ g cm}^{-3}\) and the density of butan-1-ol is \(0.81\text{ g cm}^{-3}\). Identify which layer is the upper layer. Explain your answer. [2]

(c) Phenolphthalein is used as the indicator. State the color change at the end-point of each titration. [2]

(d) (i) Calculate the concentration of ethanoic acid in both the aqueous and organic layers. Show your working. [3]
(ii) Calculate the partition coefficient, \(K_{pc}\), of ethanoic acid between butan-1-ol and water. [1]

(e) The student repeated the experiment but used \(100.0\text{ cm}^3\) of butan-1-ol instead of \(50.0\text{ cm}^3\). State and explain the effect, if any, of this change on:
(i) the value of the partition coefficient, \(K_{pc}\). [2]
(ii) the concentration of ethanoic acid remaining in the aqueous layer. [3]