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The reaction between acidified aqueous sodium thiosulfate and hydrochloric acid produces a cloudy precipitate of sulfur.

$$\text{Na}_2\text{S}_2\text{O}_3(\text{aq}) + 2\text{HCl}(\text{aq}) \rightarrow 2\text{NaCl}(\text{aq}) + \text{S}(\text{s}) + \text{SO}_2(\text{g}) + \text{H}_2\text{O}(\text{l})$$

If the temperature of the reaction mixture is decreased from \(50\ ^\circ\text{C}\) to \(20\ ^\circ\text{C}\), how do the activation energy, \(E_\text{a}\), and the proportion of colliding molecules with energy greater than or equal to \(E_\text{a}\) change?

An excess of water is added to two separate test-tubes, one containing liquid silicon(IV) chloride, \(\text{SiCl}_4\), and the other containing solid phosphorus(V) chloride, \(\text{PCl}_5\).

Which statement about the observations and the pH of the resulting solutions is correct?

A student added \(2.02\text{ g}\) of potassium nitrate (\(\text{KNO}_3\), \(M_\text{r} = 101.1\)) to \(50.0\text{ cm}^3\) of water in a polystyrene cup. The temperature of the water fell from \(21.4\ ^\circ\text{C}\) to \(18.2\ ^\circ\text{C}\).

Assume the mass of the resulting solution is \(50.0\text{ g}\) and its specific heat capacity is \(4.18\text{ J g}^{-1}\ ^\circ\text{C}^{-1}\).

What is the standard enthalpy change of solution, \(\Delta H_\text{sol}^\ominus\), of potassium nitrate?

How many stereoisomers (including both optical and cis-trans isomers) exist for the compound 4-methylhept-5-en-2-ol?

In the reaction between potassium dichromate(VI) and hydrogen sulfide in acidic solution, the chemical equation is:

$$\text{Cr}_2\text{O}_7^{2-}(\text{aq}) + 8\text{H}^+(\text{aq}) + 3\text{H}_2\text{S}(\text{aq}) \rightarrow 2\text{Cr}^{3+}(\text{aq}) + 3\text{S}(\text{s}) + 7\text{H}_2\text{O}(\text{l})$$

Which row correctly identifies the changes in the oxidation number of chromium and sulfur?

A mixture of \(1.00\text{ mol}\) of nitrogen gas and \(3.00\text{ mol}\) of hydrogen gas is allowed to reach equilibrium in a sealed vessel of volume \(2.00\text{ dm}^3\) at a constant temperature.

$$\text{N}_2(\text{g}) + 3\text{H}_2(\text{g}) \rightleftharpoons 2\text{NH}_3(\text{g})$$

At equilibrium, \(0.40\text{ mol}\) of ammonia is present in the mixture.

What is the value of the equilibrium constant, \(K_\text{c}\), at this temperature?

The standard enthalpy changes of formation, \(\Delta H_\text{f}^\ominus\), for some substances are given below:
- \(\text{CO}_2(\text{g}) = -393.5\text{ kJ mol}^{-1}\)
- \(\text{H}_2\text{O}(\text{l}) = -285.8\text{ kJ mol}^{-1}\)
- \(\text{CH}_3\text{OCH}_3(\text{g}) = -184.1\text{ kJ mol}^{-1}\)

What is the standard enthalpy change of combustion, \(\Delta H_\text{c}^\ominus\), of dimethyl ether, \(\text{CH}_3\text{OCH}_3(\text{g})\)?

Four different halogenoalkanes are heated separately with aqueous silver nitrate in ethanol at \(50\ ^\circ\text{C}\).

Which halogenoalkane reacts fastest to form a precipitate of silver halide?

The temperature of a reaction mixture is increased by \(10\,^\circ\text{C}\). What happens to the activation energy, \(E_a\), the total frequency of collisions, and the fraction of collisions with energy greater than or equal to \(E_a\)?

A white solid oxide of a Period 3 element, \(X\), reacts violently with water to form a strongly acidic solution. A different liquid chloride of a Period 3 element, \(Y\), also reacts violently with water to form a strongly acidic solution and white fumes.

What could be the identities of \(X\) and \(Y\)?

In a calorimetry experiment, \(50.0\text{ cm}^3\) of \(1.00\text{ mol dm}^{-3}\) \(NaOH(aq)\) is mixed with \(50.0\text{ cm}^3\) of \(1.00\text{ mol dm}^{-3}\) \(HCl(aq)\) in a polystyrene cup. The temperature of both solutions is initially \(22.0\,^\circ\text{C}\). After mixing, the maximum temperature reached is \(28.7\,^\circ\text{C}\).

Assuming the density of the final mixture is \(1.00\text{ g cm}^{-3}\) and its specific heat capacity is \(4.18\text{ J g}^{-1}\text{ K}^{-1}\), what is the enthalpy change of neutralisation, \(\Delta H_n\), in \(\text{kJ mol}^{-1}\)?

How many isomeric esters have the molecular formula \(\text{C}_4\text{H}_8\text{O}_2\)?

In acidic solution, manganate(VII) ions oxidize tin(II) ions to tin(IV) ions, and are themselves reduced to manganese(II) ions.

The unbalanced ionic equation is:
\(a\,\text{MnO}_4^-(aq) + b\,\text{Sn}^{2+}(aq) + c\,\text{H}^+(aq) \rightarrow d\,\text{Mn}^{2+}(aq) + e\,\text{Sn}^{4+}(aq) + f\,\text{H}_2\text{O}(l)\)

What is the ratio \(b : a\) in the balanced equation?

The following exothermic reaction is in a state of dynamic equilibrium in a closed vessel:

\(2\text{SO}_2(g) + \text{O}_2(g) \rightleftharpoons 2\text{SO}_3(g) \quad \Delta H = -197\text{ kJ mol}^{-1}\)

Which of the following changes will result in an increase in both the equilibrium constant, \(K_p\), and the equilibrium yield of \(\text{SO}_3(g)\)?

Using the standard enthalpy changes of formation provided in the table, what is the standard enthalpy change of combustion, \(\Delta H_c^\ominus\), of methane, \(\text{CH}_4(g)\), in \(\text{kJ mol}^{-1}\)?

| Substance | \(\Delta H_f^\ominus\text{ / kJ mol}^{-1}\) |
|---|---|
| \(\text{CH}_4(g)\) | \(-74.8\) |
| \(\text{CO}_2(g)\) | \(-393.5\) |
| \(\text{H}_2\text{O}(l)\) | \(-285.8\) |

The rates of hydrolysis of 1-chlorobutane, 1-bromobutane, and 1-iodobutane are compared by reacting them with aqueous silver nitrate in ethanol at \(50\,^\circ\text{C\)}.

Which of the following correctly describes the order of rate of reaction (from fastest to slowest) and identifies the correct reason for this trend?

The diagram shows a Maxwell-Boltzmann distribution of molecular energies for a gas-phase reaction. Which statement is correct when the temperature of the gas is increased at constant volume?

Two Period 3 elements, \(X\) and \(Y\), react separately with oxygen to form oxides. The oxide of \(X\) dissolves in water to form a solution with a pH of approximately 2. The oxide of \(Y\) is insoluble in water but reacts with both aqueous sodium hydroxide and dilute hydrochloric acid. Which elements are \(X\) and \(Y\)?

In a calorimetry experiment, \(100\text{ cm}^3\) of \(1.0\text{ mol dm}^{-3}\) \(\text{HCl(aq)}\) is mixed with \(100\text{ cm}^3\) of \(1.0\text{ mol dm}^{-3}\) \(\text{NaOH(aq)}\) in a polystyrene cup. The temperature rises by \(5.8\text{ }^{\circ}\text{C}\). Assume the density of the solution is \(1.0\text{ g cm}^{-3}\) and its specific heat capacity is \(4.2\text{ J g}^{-1}\text{ K}^{-1}\). What is the standard enthalpy change of neutralisation, \(\Delta H_{\text{neut}}\), for this reaction?

How many isomers with the molecular formula \(\text{C}_4\text{H}_8\) can decolourise a solution of bromine in an organic solvent?

When hot concentrated sulfuric acid reacts with solid potassium iodide, several products are formed including \(\text{I}_2\), \(\text{H}_2\text{S}\), \(\text{SO}_2\), and \(\text{S}\). In which product does sulfur have the lowest oxidation state?

The following equilibrium is established in a closed container at temperature \(T\):
\[\text{PCl}_5\text{(g)} \rightleftharpoons \text{PCl}_3\text{(g)} + \text{Cl}_2\text{(g)} \quad \Delta H = +88\text{ kJ mol}^{-1}\]
Which change will result in an increase in the value of the equilibrium constant, \(K_c\)?

Consider the following standard enthalpy changes of formation, \(\Delta H_{\text{f}}^{\ominus}\):
- \(\Delta H_{\text{f}}^{\ominus}[\text{CO}_2\text{(g)}] = -393.5\text{ kJ mol}^{-1}\)
- \(\Delta H_{\text{f}}^{\ominus}[\text{H}_2\text{O(l)}] = -285.8\text{ kJ mol}^{-1}\)
- \(\Delta H_{\text{f}}^{\ominus}[\text{C}_2\text{H}_5\text{OH(l)}] = -277.6\text{ kJ mol}^{-1}\)

What is the standard enthalpy change of combustion, \(\Delta H_{\text{c}}^{\ominus}\), of liquid ethanol, \(\text{C}_2\text{H}_5\text{OH(l)}\)?

Three different halogenoalkanes, 1-chlorobutane, 1-bromobutane, and 1-iodobutane, are reacted separately with aqueous silver nitrate in ethanol at \(50\text{ }^{\circ}\text{C}\). Which statement correctly explains the relative rates of these reactions?

Dilute hydrochloric acid reacts with excess marble chips (calcium carbonate) to produce carbon dioxide gas.

$$\text{CaCO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CaCl}_2(\text{aq}) + \text{CO}_2(\text{g}) + \text{H}_2\text{O}(\text{l})$$

Which of the following changes will increase the initial rate of the reaction while keeping the total volume of carbon dioxide gas collected constant?

An oxide of a Period 3 element, \(X\), dissolves in water to form a solution with a pH less than 3.

A chloride of a different Period 3 element, \(Y\), reacts vigorously with water to form a strongly acidic solution and a white precipitate.

What are the identities of elements \(X\) and \(Y\)?

A student carries out a calorimetry experiment to determine the enthalpy change of combustion of propan-1-ol, \(\text{CH}_3\text{CH}_2\text{CH}_2\text{OH}\) (\(M_r = 60.0\)).

A burner containing propan-1-ol is weighed before and after combustion.

- Mass of propan-1-ol burned = \(0.60\text{ g}\)
- Mass of water in the copper calorimeter = \(100.0\text{ g}\)
- Temperature rise of the water = \(12.0\text{ }^{\circ}\text{C}\)
- Specific heat capacity of water = \(4.18\text{ J g}^{-1}\text{ K}^{-1}\)

What is the experimental value of the standard enthalpy change of combustion, \(\Delta H_c\), of propan-1-ol from this experiment?

How many stereoisomers exist for 3-methylhex-4-en-3-ol?

In which of the following reactions does the oxidation number of the underlined carbon element increase by exactly 4?

The following reaction is in dynamic equilibrium in a closed vessel at temperature \(T\):

$$\text{PCl}_5(\text{g}) \rightleftharpoons \text{PCl}_3(\text{g}) + \text{Cl}_2(\text{g}) \quad \Delta H = +88\text{ kJ mol}^{-1}$$

Which of the following changes will increase the value of the equilibrium constant, \(K_c\)?

Using the following standard enthalpy changes:

- \(\Delta H_f^{\ominus}[\text{CO}_2(\text{g})] = -393.5\text{ kJ mol}^{-1}\)
- \(\Delta H_f^{\ominus}[\text{H}_2\text{O}(\text{l})] = -285.8\text{ kJ mol}^{-1}\)
- \(\Delta H_c^{\ominus}[\text{CH}_3\text{OCH}_3(\text{g})] = -1460.0\text{ kJ mol}^{-1}\)

What is the standard enthalpy change of formation, \(\Delta H_f^{\ominus}\), of dimethyl ether, \(\text{CH}_3\text{OCH}_3(\text{g})\)?

Four different halogenoalkanes are heated separately with aqueous silver nitrate in ethanol at \(50\text{ }^{\circ}\text{C}\).

Which halogenoalkane will produce a precipitate the fastest?

Which statement correctly explains why an increase in temperature increases the rate of a chemical reaction?

Two Period 3 elements, \(X\) and \(Y\), react separately with oxygen to form the oxides \(XO_2\) and \(Y_2O_3\) respectively. \(XO_2\) is a gas at room temperature that dissolves in water to form an acidic solution. \(Y_2O_3\) is a solid at room temperature that is insoluble in water.

Which statement is correct?

In an experiment to determine the enthalpy change of combustion of methanol, \(\text{CH}_3\text{OH}\), a student burned \(0.80\text{ g}\) of methanol. The heat released was used to raise the temperature of \(100.0\text{ g}\) of water from \(20.0\ ^\circ\text{C}\) to \(45.0\ ^\circ\text{C}\).

Only \(70\%\) of the heat released by the combustion was absorbed by the water.

[Specific heat capacity of water, \(c = 4.18\text{ J g}^{-1}\text{ K}^{-1}\); \(M_{\text{r}}\) of methanol = \(32.0\)]

What is the calculated experimental enthalpy change of combustion of methanol?

An acyclic organic compound \(W\) has the molecular formula \(\text{C}_4\text{H}_7\text{Cl}\) and contains a chiral carbon atom. When \(W\) reacts with hydrogen in the presence of a nickel catalyst, compound \(Z\) is formed.

Which statement about \(W\) and \(Z\) is correct?

An acidified solution containing \(0.020\text{ mol}\) of \(\text{XO}_4^-\) ions is completely reduced by \(0.050\text{ mol}\) of \(\text{SO}_3^{2-}\) ions. During this reaction, the sulfite ions are oxidized to sulfate ions, \(\text{SO}_4^{2-}\).

What is the final oxidation state of the element \(X\) after reduction?

The reversible reaction below is in dynamic equilibrium in a sealed container of fixed volume at \(250\ ^\circ\text{C}\):

\(\text{PCl}_5\text{(g)} \rightleftharpoons \text{PCl}_3\text{(g)} + \text{Cl}_2\text{(g)} \quad \Delta H = +88\text{ kJ mol}^{-1}\)

Which change would result in an increase in the partial pressure of \(\text{Cl}_2\text{(g)}\) at the new equilibrium?

The standard enthalpy changes of combustion, \(\Delta H_{\text{c}}^\theta\), of three substances are listed below:

- \(\text{C(s)}\): \(-394\text{ kJ mol}^{-1}\)
- \(\text{H}_2\text{(g)}\): \(-286\text{ kJ mol}^{-1}\)
- \(\text{CH}_3\text{CH}_2\text{COOH(l)}\): \(-1527\text{ kJ mol}^{-1}\)

What is the standard enthalpy change of formation of propanoic acid, \(\Delta H_{\text{f}}^\theta [\text{CH}_3\text{CH}_2\text{COOH(l)}]\)?

Equal amounts of \(1\)-chlorobutane, \(1\)-bromobutane, and \(1\)-iodobutane are heated separately with aqueous silver nitrate in ethanol under identical conditions.

Which row correctly identifies the fastest halogenoalkane to hydrolyze and the correct explanation?

This question is about reaction kinetics.

(a) Define the term *activation energy*, \(E_a\). [1]

(b) Describe and explain how an increase in temperature affects the rate of a chemical reaction using the Maxwell-Boltzmann distribution of molecular energies. Your response should describe how the shape of the curve changes at a higher temperature and how this relates to successful collisions. [5]

(c) Draw a mental picture or describe the positions on a Maxwell-Boltzmann energy distribution curve of the activation energy of an uncatalysed reaction, \(E_a\), compared to a catalysed reaction, \(E_c\).
Explain, in terms of activation energy and collision frequency, how a catalyst increases the rate of a chemical reaction. [4]

(d) The reaction between peroxodisulfate ions, \(\text{S}_2\text{O}_8^{2-}\), and iodide ions, \(\text{I}^-\), is very slow in the absence of a catalyst.
(i) Write an ionic equation for this reaction. [1]
(ii) Explain why this reaction has a high activation energy in the absence of a catalyst. [2]
(iii) Aqueous iron(II) ions, \(\text{Fe}^{2+}(\text{aq})\), act as a homogeneous catalyst for this reaction. Write two equations to show how \(\text{Fe}^{2+}(\text{aq})\) acts as a catalyst in this reaction. [2]

This question is about Period 3 elements and their oxides.

(a) Describe what is observed and write a balanced chemical equation when the following elements are heated and reacted with oxygen:
(i) Sodium [2]
(ii) Phosphorus [2]

(b) Sodium oxide, \(\text{Na}_2\text{O}\), and sulfur trioxide, \(\text{SO}_3\), are oxides of Period 3 elements.
(i) State the type of bonding present in each of these oxides. [2]
(ii) Write chemical equations for the separate reactions of sodium oxide and sulfur trioxide with water. State the approximate pH of the resulting solution in each case. [4]

(c) Aluminium oxide, \(\text{Al}_2\text{O}_3\), is amphoteric.
(i) State what is meant by the term *amphoteric*. [1]
(ii) Write ionic equations to demonstrate the amphoteric nature of aluminium oxide. Your equations must show its reaction with an acid and its reaction with a strong alkali. [4]

This question is about chemical energetics and Hess's law.

(a) Define the term *standard enthalpy change of formation*, \(\Delta H_f^\ominus\). [2]

(b) The standard enthalpy changes of combustion, \(\Delta H_c^\ominus\), at 298 K for carbon, hydrogen, and propanoic acid, \(\text{C}_2\text{H}_5\text{COOH}(\text{l})\), are given below:
- Carbon, \(\text{C}(\text{s})\): \(-393.5\text{ kJ mol}^{-1}\)
- Hydrogen, \(\text{H}_2(\text{g})\): \(-285.8\text{ kJ mol}^{-1}\)
- Propanoic acid, \(\text{C}_2\text{H}_5\text{COOH}(\text{l})\): \(-1527.3\text{ kJ mol}^{-1}\)

(i) Write the balanced chemical equation, including state symbols, for the reaction representing the standard enthalpy change of formation of propanoic acid. [2]
(ii) Draw a Hess's law cycle showing the relationship between these standard enthalpy changes of combustion and the standard enthalpy change of formation of propanoic acid. Label all enthalpy changes clearly. [2]
(iii) Calculate the standard enthalpy change of formation, \(\Delta H_f^\ominus\), of propanoic acid. [3]

(c) A student carried out a calorimetry experiment to determine the enthalpy change of neutralization.
\(50.0\text{ cm}^3\) of \(1.00\text{ mol dm}^{-3}\) \(\text{HCl}(\text{aq})\) was mixed with \(50.0\text{ cm}^3\) of \(1.00\text{ mol dm}^{-3}\) \(\text{NaOH}(\text{aq})\) in a polystyrene cup. The initial temperature of both solutions was \(21.4\ ^\circ\text{C}\) and the maximum temperature reached was \(28.1\ ^\circ\text{C}\).

(i) Calculate the heat energy, \(q\), in kJ, released during this neutralization reaction. Show your working and state one major assumption you made in your calculation. [Assume the density of the final mixture is \(1.00\text{ g cm}^{-3}\) and its specific heat capacity is \(4.18\text{ J g}^{-1}\ \text{K}^{-1}\)]. [3]
(ii) Calculate the standard enthalpy change of neutralization, \(\Delta H_{neu}\), in \(\text{kJ mol}^{-1}\), for this reaction. Include the appropriate sign. [3]

This question is about halogenoalkanes and their isomerism.

(a) Compound A is a halogenoalkane with the molecular formula \(\text{C}_4\text{H}_9\text{Br}\).
(i) Draw the skeletal structures of all four structural isomers of \(\text{C}_4\text{H}_9\text{Br}\). Underneath each structure, state its IUPAC name. [4]
(ii) Identify the structural isomer of \(\text{C}_4\text{H}_9\text{Br}\) that exhibits optical isomerism. Explain why this isomer is optically active, and describe how the structures of its two enantiomers are related. [4]

(b) When 2-bromo-2-methylpropane is heated with aqueous sodium hydroxide, 2-methylpropan-2-ol is formed.
(i) State the name of the reaction mechanism. [1]
(ii) Describe this reaction mechanism using curly arrows to show the movement of electron pairs. Show the structures of the organic reactant, intermediate, and product, as well as any inorganic ions involved. [4]
(iii) Explain why 2-bromo-2-methylpropane reacts via this mechanism rather than the alternative substitution mechanism favoured by primary halogenoalkanes. [2]

In this experiment, you will determine the value of \( x \) in the formula of hydrated sodium thiosulfate, \( \text{Na}_2\text{S}_2\text{O}_3 \cdot x\text{H}_2\text{O} \), by titrating a solution of this salt against iodine. Iodine is generated in situ by reacting a standard solution of potassium iodate(V), \( \text{KIO}_3 \), with excess potassium iodide, \( \text{KI} \), in acidic conditions. Equation 1: \( \text{IO}_3^-(\text{aq}) + 5\text{I}^-(\text{aq}) + 6\text{H}^+(\text{aq}) \rightarrow 3\text{I}_2(\text{aq}) + 3\text{H}_2\text{O}(\text{l}) \) and Equation 2: \( \text{I}_2(\text{aq}) + 2\text{S}_2\text{O}_3^{2-}(\text{aq}) \rightarrow 2\text{I}^-(\text{aq}) + \text{S}_4\text{O}_6^{2-}(\text{aq}) \). Chemicals provided: FB 1 is a solution containing \( 24.80\text{ g dm}^{-3} \) of hydrated sodium thiosulfate, \( \text{Na}_2\text{S}_2\text{O}_3 \cdot x\text{H}_2\text{O} \). FB 2 is \( 0.0150\text{ mol dm}^{-3} \) potassium iodate(V), \( \text{KIO}_3 \). FB 3 is \( 1.0\text{ mol dm}^{-3} \) sulfuric acid, \( \text{H}_2\text{SO}_4 \). FB 4 is \( 0.5\text{ mol dm}^{-3} \) potassium iodide, \( \text{KI} \). Starch indicator. Method: 1. Fill a burette with FB 1. 2. Pipette \( 25.0\text{ cm}^3 \) of FB 2 into a conical flask. 3. Use a measuring cylinder to add about \( 10\text{ cm}^3 \) of FB 3 and \( 10\text{ cm}^3 \) of FB 4 to the flask. The solution turns dark brown. 4. Titrate the mixture with FB 1 until the brown color fades to light yellow. 5. Add a few drops of starch indicator to turn the solution blue-black. 6. Continue adding FB 1 dropwise until the blue-black color disappears, leaving a colorless solution. (a) Prepare a table for your titration results, showing clearly the initial and final burette readings, and the volume of FB 1 added for each titration. State the volume of FB 1 to be used in your calculations. (b) Calculate the number of moles of iodate(V) ions, \( \text{IO}_3^- \), in \( 25.0\text{ cm}^3 \) of FB 2. (c) Show that \( 1.00\text{ mol} \) of \( \text{IO}_3^- \) reacts to produce iodine that requires \( 6.00\text{ mol} \) of \( \text{S}_2\text{O}_3^{2-} \) for complete reaction. (d) Calculate the concentration of sodium thiosulfate in FB 1 in \( \text{mol dm}^{-3} \), assuming a mean titre of \( 22.50\text{ cm}^3 \). (e) Using the concentration calculated in (d) and the mass concentration of FB 1 (\( 24.80\text{ g dm}^{-3} \)), calculate the experimental relative formula mass of \( \text{Na}_2\text{S}_2\text{O}_3 \cdot x\text{H}_2\text{O} \) and determine the value of \( x \). [\( A_r \): \( \text{Na} = 23.0 \), \( \text{S} = 32.1 \), \( \text{O} = 16.0 \), \( \text{H} = 1.0 \)] (f) Identify one potential source of systematic error in this practical procedure and suggest an improvement to minimize it.

In this experiment, you will determine the enthalpy change of hydration of anhydrous copper(II) sulfate, \( \text{CuSO}_4 \), by applying Hess's Law. You will measure the temperature changes that occur when anhydrous copper(II) sulfate and hydrated copper(II) sulfate are separately dissolved in water. Chemicals and apparatus provided: FB 1 is anhydrous copper(II) sulfate powder, \( \text{CuSO}_4 \). FB 2 is hydrated copper(II) sulfate crystals, \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} \). Plastic cup (calorimeter) and thermometer. Method: Experiment 1: Dissolving FB 1. 1. Support the plastic cup in a beaker. Transfer \( 50.0\text{ cm}^3 \) of distilled water into the cup. 2. Record the temperature of the water every minute for 3 minutes. 3. At \( t = 4\text{ minutes} \), add \( 3.99\text{ g} \) of FB 1. Stir continuously. 4. Record the temperature of the solution every minute from \( t = 5\text{ minutes} \) to \( t = 10\text{ minutes} \). Experiment 2: Dissolving FB 2. Repeat the procedure but use \( 45.0\text{ cm}^3 \) of water and add \( 6.24\text{ g} \) of FB 2 at \( t = 4\text{ minutes} \). (a) Use your extrapolated temperature-time values to determine the corrected maximum temperature change, \( \Delta T_1 \), for Experiment 1 and the corrected minimum temperature change, \( \Delta T_2 \), for Experiment 2. Assume experimental values of \( \Delta T_1 = +11.5\text{ }^\circ\text{C} \) and \( \Delta T_2 = -1.5\text{ }^\circ\text{C} \). (b) Calculate the heat energy change, \( q_1 \), in joules, when FB 1 dissolves in Experiment 1. [Assume the specific heat capacity of the solution is \( 4.18\text{ J g}^{-1}\text{ }^\circ\text{C}^{-1} \) and the mass of the solution is \( 50.0\text{ g} \)]. (c) Calculate the enthalpy change of solution for anhydrous copper(II) sulfate, \( \Delta H_1 \), in \( \text{kJ mol}^{-1} \). [\( M_r \) of \( \text{CuSO}_4 = 159.6 \)]. (d) Calculate the enthalpy change of solution for hydrated copper(II) sulfate, \( \Delta H_2 \), in \( \text{kJ mol}^{-1} \). [\( M_r \) of \( \text{CuSO}_4 \cdot 5\text{H}_2\text{O} = 249.6 \); assume mass of solution is \( 50.0\text{ g} \)]. (e) Use Hess's Law to construct an energy cycle and calculate the enthalpy change of hydration, \( \Delta H_{\text{hyd}} \), of anhydrous copper(II) sulfate: \( \text{CuSO}_4(\text{s}) + 5\text{H}_2\text{O}(\text{l}) \rightarrow \text{CuSO}_4 \cdot 5\text{H}_2\text{O}(\text{s}) \). (f) State one source of heat loss in this experiment and suggest a practical improvement to minimize it.

In this experiment, you will investigate how the concentration of hydrochloric acid affects the rate of its reaction with magnesium. Equation: \( \text{Mg}(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{MgCl}_2(\text{aq}) + \text{H}_2(\text{g}) \). The rate of reaction is measured by timing how long it takes for a fixed length of magnesium ribbon to completely dissolve. Chemicals provided: FB 1 is \( 2.00\text{ mol dm}^{-3} \) hydrochloric acid, \( \text{HCl} \). FB 2 is distilled water. Five \( 2.0\text{ cm} \) pieces of magnesium ribbon. Method: 1. Prepare 5 reaction mixtures with total volume \( 10.0\text{ cm}^3 \) in five test-tubes: Tube 1 (\( 10.0\text{ cm}^3 \) FB 1, \( 0.0\text{ cm}^3 \) FB 2); Tube 2 (\( 8.0\text{ cm}^3 \) FB 1, \( 2.0\text{ cm}^3 \) FB 2); Tube 3 (\( 6.0\text{ cm}^3 \) FB 1, \( 4.0\text{ cm}^3 \) FB 2); Tube 4 (\( 4.0\text{ cm}^3 \) FB 1, \( 6.0\text{ cm}^3 \) FB 2); Tube 5 (\( 2.0\text{ cm}^3 \) FB 1, \( 8.0\text{ cm}^3 \) FB 2). 2. Add one piece of Mg ribbon to Tube 1 and record the time, \( t \), in seconds for the magnesium to completely disappear. 3. Repeat for tubes 2 to 5. (a) Prepare a table to record your results, showing the volumes of FB 1 and FB 2, the concentration of HCl, the reaction time \( t \), and the rate of reaction represented by \( 1/t \). (b) Assume that for Tube 1, \( t = 24\text{ s} \), and for Tube 3, \( t = 67\text{ s} \). Calculate the concentration of \( \text{HCl} \) in Tube 1 and Tube 3. (c) Briefly describe the shape of the graph obtained when plotting \( 1/t \) against the concentration of \( \text{HCl} \). (d) Deduce the order of reaction with respect to hydrochloric acid based on the relationship between rate (\( 1/t \)) and concentration. (e) A student suggests that using a larger volume of the reaction mixture (e.g., doubling the volume of both FB 1 and FB 2, keeping the concentration the same) would decrease the reaction time. State whether the student is correct and explain your answer.