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Propene reacts with steam in the presence of an acid catalyst to form propanol. Under which conditions does this reaction occur, and what is the change in the color of aqueous bromine when it is added to propene?

A student wants to investigate the rate of reaction between calcium carbonate and dilute hydrochloric acid by measuring the volume of carbon dioxide gas released over time. Which pieces of apparatus are most suitable to measure the volume of gas and the time taken?

A solid X is dissolved in water to make an aqueous solution. Portions of this solution are tested as follows:
1. Addition of aqueous sodium hydroxide produces a green precipitate that is insoluble in excess.
2. Addition of dilute nitric acid followed by aqueous barium nitrate produces a white precipitate.
What is the identity of compound X?

Which statement about endothermic reactions is correct?

Metal M is heated with the oxides of three other metals: copper, iron, and zinc. The results are shown below:
- M + copper(II) oxide \(\rightarrow\) reaction occurs
- M + iron(II) oxide \(\rightarrow\) no reaction
- M + zinc oxide \(\rightarrow\) no reaction
What is a possible identity of metal M?

Chlorine has two naturally occurring isotopes: \(^{35}\text{Cl}\) and \(^{37}\text{Cl}\). Which statement about these isotopes is correct?

A mixture contains copper(II) sulfate (soluble in water) and sand (insoluble in water). A student wants to obtain pure, dry crystals of copper(II) sulfate and dry sand from this mixture. In which order should the student carry out the processes?

Which statement about the giant covalent structures of diamond, graphite, and silicon(IV) oxide is correct?

An atom of element X has 19 protons and 20 neutrons. An atom of element Y has 17 protons and 18 neutrons. Which statement about X and Y is correct?

Dilute sulfuric acid is electrolysed using inert platinum electrodes. Which statement describes the reaction at the anode (positive electrode)?

What is the total number of shared pairs of electrons in one molecule of methanol, \(CH_3OH\)?

Ethene is reacted with steam to manufacture ethanol. Which set of conditions is used for this industrial process?

A student investigates the rate of reaction between excess calcium carbonate chips and dilute hydrochloric acid by measuring the volume of gas produced. Which set of apparatus is essential to collect the data needed to plot a rate graph?

An aqueous solution contains \(Cr^{3+}\) ions. What is observed when aqueous sodium hydroxide is added dropwise and then in excess to this solution?

The reaction between nitrogen and hydrogen to form ammonia is exothermic: \(N_2(g) + 3H_2(g) \rightarrow 2NH_3(g)\). Which statement explains why this reaction is exothermic?

A student wants to obtain a pure sample of liquid water from aqueous sodium chloride. Which experimental method should the student use?

An atom of element X has 17 protons and 18 neutrons. An atom of element Y has 17 protons and 20 neutrons. Which statement about X and Y is correct?

The electrolysis of concentrated aqueous sodium chloride is carried out using inert electrodes. Which row correctly identifies the products at each electrode and the change in pH of the electrolyte during the electrolysis? Row A: cathode product is hydrogen, anode product is chlorine, pH increases. Row B: cathode product is sodium, anode product is chlorine, pH decreases. Row C: cathode product is hydrogen, anode product is oxygen, pH has no change. Row D: cathode product is sodium, anode product is oxygen, pH increases.

Hydrocarbon W reacts with steam in the presence of an acid catalyst to form an alcohol with the molecular formula \(C_4H_{10}O\). Which statement about hydrocarbon W is correct?

Which statement about the macromolecular structure of silicon(IV) oxide, \(SiO_2\), is correct?

A student wants to investigate the rate of reaction between calcium carbonate (marble chips) and dilute hydrochloric acid by measuring the volume of gas produced over time. Which set of apparatus is most suitable for this investigation?

A pale green or colorless solution is tested. When aqueous sodium hydroxide is added, a green precipitate is formed which is insoluble in excess. When dilute nitric acid followed by aqueous barium nitrate is added, a white precipitate is formed. Which compound is present in the solution?

A chemical reaction has a reaction pathway diagram where the energy level of the products is higher than the energy level of the reactants. Which row correctly describes this reaction? Row A: reaction is endothermic, sign of enthalpy change is positive (+), reactants have less energy than products. Row B: reaction is exothermic, sign of enthalpy change is negative (-), reactants have more energy than products. Row C: reaction is endothermic, sign of enthalpy change is negative (-), reactants have more energy than products. Row D: reaction is exothermic, sign of enthalpy change is positive (+), reactants have less energy than products.

Four metals, P, Q, R, and S, were tested under different conditions. Metal P reacts rapidly with cold water to produce hydrogen gas. The oxide of metal Q can be reduced to the metal when heated with carbon. Metal R does not react with dilute hydrochloric acid, but its oxide cannot be decomposed by heating alone. Metal S is obtained by heating its oxide alone. What is the order of reactivity of the metals, from most reactive to least reactive?

A student wants to obtain a pure sample of solid cobalt(II) chloride from an aqueous solution of cobalt(II) chloride. Which sequence of steps should the student carry out?

An ion of an isotope of element \(X\) is represented as \({}_{34}^{79}X^{2-}\). Which row in the table shows the correct number of protons, neutrons, and electrons in this ion?

$$\begin{array}{|c|c|c|c|} \hline & \text{protons} & \text{neutrons} & \text{electrons} \\ \hline \text{A} & 34 & 45 & 32 \\ \hline \text{B} & 34 & 45 & 36 \\ \hline \text{C} & 34 & 79 & 36 \\ \hline \text{D} & 36 & 45 & 34 \\ \hline \end{array}$$

Methanol, \(\text{CH}_3\text{OH}\), is a simple covalent molecule. What is the total number of shared pairs of electrons (bonding pairs) in one molecule of methanol?

An organic compound \(Y\) reacts with steam in the presence of an acid catalyst to produce an alcohol with the molecular formula \(\text{C}_4\text{H}_{10}\text{O}\). What is a possible structure for compound \(Y\)?

A student investigates the rate of reaction between dilute hydrochloric acid and excess calcium carbonate lumps:

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

Which piece of apparatus, when used with a stopwatch, is **least** suitable for measuring the rate of this reaction?

Aqueous copper(II) sulfate is electrolysed using inert carbon (graphite) electrodes. What are the products formed at the anode and cathode?

The reaction between nitrogen and hydrogen to form ammonia is exothermic:

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

Which statement about this reaction is correct?

Three metals, \(W\), \(X\), and \(Y\), are tested to determine their relative reactivity.

- Only metal \(Y\) reacts with cold water to produce a gas.
- Metal \(W\) does not react with dilute hydrochloric acid, but metal \(X\) does react with dilute hydrochloric acid.
- When the oxide of metal \(W\) is heated with metal \(X\), a displacement reaction occurs.

What is the order of reactivity of these three metals, starting with the **most** reactive?

A solid mixture contains sodium chloride, sulfur, and sand. Sodium chloride is soluble in water but insoluble in hexane. Sulfur is insoluble in water but soluble in hexane. Sand is insoluble in both water and hexane. Which sequence of steps can be used to obtain a pure, dry sample of sand from this mixture?

What is the total number of bonding pairs of electrons and lone pairs of electrons (non-bonding outer-shell electrons) in one molecule of methanol, \(\text{CH}_3\text{OH}\)?

An organic compound \(Y\) has the molecular formula \(\text{C}_4\text{H}_8\). It reacts with bromine water to decolourise it. Which structure could represent the product of this reaction?

A student wants to investigate how the rate of reaction between zinc and dilute sulfuric acid changes with temperature. Which variables must be kept constant to ensure a fair test?

1. The mass of the zinc
2. The concentration of the sulfuric acid
3. The temperature of the sulfuric acid
4. The volume of the sulfuric acid

An aqueous solution of salt \(Z\) is tested using two separate reactions:

- When aqueous sodium hydroxide is added, a green precipitate is formed which is insoluble in excess.
- When dilute nitric acid is added followed by aqueous barium nitrate, a white precipitate is formed.

What is the identity of salt \(Z\)?

The table shows some bond energies.

| Bond | Bond energy in kJ/mol |
| :--- | :--- |
| \(\text{C–H}\) | 413 |
| \(\text{Cl–Cl}\) | 242 |
| \(\text{C–Cl}\) | 339 |
| \(\text{H–Cl}\) | 431 |

The equation for the chlorination of methane is:

\(\text{CH}_4 + \text{Cl}_2 \rightarrow \text{CH}_3\text{Cl} + \text{HCl}\)

What is the energy change, in kJ/mol, for this reaction?

Three metals, \(P\), \(Q\), and \(R\), have the following properties:

- Metal \(P\) reacts vigorously with cold water.
- Metal \(Q\) does not react with steam, but its oxide can be reduced to the metal by heating with carbon.
- Metal \(R\) reacts with steam but does not react with cold water.

What is the order of reactivity of these metals, from most reactive to least reactive?

An imaginary element \(X\) has two isotopes, \(^{79}X\) and \(^{81}X\).

The relative abundance of \(^{79}X\) is 60% and the relative abundance of \(^{81}X\) is 40%.

What is the relative atomic mass of element \(X\)?

An aqueous solution of copper(II) sulfate, \(\text{CuSO}_4(\text{aq})\), can be electrolyzed using different sets of electrodes.

(a) In Experiment 1, inert carbon electrodes are used.
(i) State what is observed at the anode (positive electrode). [1]
(ii) Write the ionic half-equation, including state symbols, for the reaction occurring at the anode. [2]
(iii) Describe and explain the change in color of the electrolyte during this electrolysis. [2]

(b) In Experiment 2, copper electrodes are used instead of carbon.
(i) Describe how the masses of the anode and cathode change during this experiment. [2]
(ii) State one industrial application of the electrolysis of copper(II) sulfate using copper electrodes. [1]

(c) Molten sodium chloride, \(\text{NaCl}(\text{l})\), is also electrolyzed.
(i) State the names of the products formed at each electrode:
Anode: [1]
Cathode: [1]
(ii) Explain, in terms of particles, why solid sodium chloride does not conduct electricity, but molten sodium chloride does. [2]
(iii) State the type of chemical bonding present in sodium chloride. [1.33]

Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond.

(a) Ethene, \(\text{C}_2\text{H}_4\), can be produced by cracking long-chain alkanes like decane, \(\text{C}_{10}\text{H}_{22}\).
(i) Write a balanced chemical equation for the cracking of one molecule of decane to produce one molecule of ethene and one other hydrocarbon. [1]
(ii) State the catalyst and temperature range used in industrial catalytic cracking. [2]

(b) Ethene reacts with different reagents in addition reactions.
(i) Describe a test to distinguish ethene from ethane. Include the reagent and the observations for both compounds.
Reagent: [1]
Observation with ethene: [1]
Observation with ethane: [1]
(ii) Ethene reacts with steam at high temperature and pressure in the presence of an acid catalyst.
Draw the displayed formula of the organic product formed, showing all atoms and all bonds. [2]
(iii) State the name of this organic product. [1]

(c) Butene, \(\text{C}_4\text{H}_8\), has several structural isomers.
(i) Draw the displayed structures of two structural isomers of butene. Show all atoms and bonds. [2]
(ii) Define the term structural isomers. [2.33]

A student investigates the rate of reaction between calcium carbonate (marble chips) and dilute hydrochloric acid:

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

(a)(i) Draw a labeled diagram of the assembled apparatus that can be used to measure the volume of gas produced over time. [3]
(ii) State one other physical quantity, other than the volume of gas, that could be measured to follow the rate of this reaction. [1]

(b) The student performs two experiments at 20 °C, using excess dilute hydrochloric acid of the same concentration:
- Experiment A: 5.0 g of large marble chips
- Experiment B: 5.0 g of small marble chips
(i) On a single set of axes, sketch curves to show how the volume of gas changes with time for Experiment A and Experiment B. Label each curve clearly. [3]
(ii) Explain, using collision theory, why the rate of reaction is faster in Experiment B than in Experiment A. [3]

(c) The student repeats the experiment using 5.0 g of small marble chips but at a higher temperature of 40 °C (Experiment C).
Explain, in terms of the kinetic particle theory and collision energy, why the rate of reaction is higher in Experiment C than in Experiment B. [3.33]

This question is about stoichiometry and chemical calculations.

(a) Crystals of hydrated magnesium sulfate have the formula \(\text{MgSO}_4 \cdot x\text{H}_2\text{O}\).
A student heated a sample of 4.92 g of these crystals to constant mass to drive off all the water of crystallization. The mass of anhydrous magnesium sulfate, \(\text{MgSO}_4\), remaining was 2.40 g.
(i) Calculate the mass of water lost from the crystals. [1]
(ii) Calculate the number of moles of anhydrous \(\text{MgSO}_4\) remaining.
[Relative formula mass, \(M_{\text{r}}\): \(\text{MgSO}_4 = 120\)] [1]
(iii) Calculate the number of moles of water lost.
[Relative formula mass, \(M_{\text{r}}\): \(\text{H}_2\text{O} = 18\)] [1]
(iv) Determine the value of \(x\) in \(\text{MgSO}_4 \cdot x\text{H}_2\text{O}\). [1.33]

(b) Dilute sulfuric acid reacts with sodium hydroxide solution according to the equation:

\(2\text{NaOH}(\text{aq}) + \text{H}_2\text{SO}_4(\text{aq}) \rightarrow \text{Na}_2\text{SO}_4(\text{aq}) + 2\text{H}_2\text{O}(\text{l})\)

(i) Calculate the number of moles of \(\text{NaOH}\) present in 50.0 cm³ of 0.200 mol/dm³ sodium hydroxide solution. [2]
(ii) Determine the number of moles of \(\text{H}_2\text{SO}_4\) required to neutralize this amount of \(\text{NaOH}\). [1]
(iii) Calculate the volume, in cm³, of 0.100 mol/dm³ \(\text{H}_2\text{SO}_4\) required for complete neutralization. [2]

(c) Magnesium reacts with dilute hydrochloric acid to produce hydrogen gas:

\(\text{Mg}(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{MgCl}_2(\text{aq}) + \text{H}_2(\text{g})\)

Calculate the volume of hydrogen gas, in dm³ at r.t.p., produced when 0.36 g of magnesium reacts completely with excess dilute hydrochloric acid.
[Relative atomic mass, \(A_{\text{r}}\): \(\text{Mg} = 24\); molar volume of gas at r.t.p. = 24 dm³/mol] [4]

This question is about identifying ions and gases.

(a) Solid salt D is dissolved in water to make an aqueous solution. Portions of this solution are tested as follows:
(i) Addition of aqueous sodium hydroxide produces a green precipitate that is insoluble in excess.
Identify the cation present in D. [1]
(ii) Addition of dilute nitric acid followed by aqueous barium nitrate produces a white precipitate.
Identify the anion present in D. [1]
(iii) Write the chemical formula of salt D. [1]

(b) Gas E is a colorless, pungent gas that turns damp red litmus paper blue.
(i) State the name of gas E. [1]
(ii) Describe how you would test for the presence of chloride ions in an aqueous solution, and state the positive result. [2]

(c) An aqueous solution of salt F contains a transition metal cation.
(i) When aqueous ammonia is added dropwise, a light blue precipitate is formed. When excess aqueous ammonia is added, the precipitate dissolves to form a deep blue solution.
Identify the cation present in salt F. [2]
(ii) Write the ionic equation (including state symbols) for the formation of the light blue precipitate when hydroxide ions, \(\text{OH}^-(\text{aq})\), react with the cation identified in (c)(i). [2]

(d) Describe a chemical test to confirm the presence of carbonate ions, \(\text{CO}_3^{2-}\), in a solid sample. Include the reagent used and the positive observation. [3.33]

This question is about chemical energetics and bond energy calculations.

(a) Hydrogen reacts with chlorine to form hydrogen chloride gas:

\(\text{H}_2(\text{g}) + \text{Cl}_2(\text{g}) \rightarrow 2\text{HCl}(\text{g})\)

This reaction is exothermic.
(i) Draw an energy level diagram for this reaction on paper. Describe your diagram by stating:
- the relative position of the reactants and products [1]
- how the activation energy, \(E_{\text{a}}\), is represented [1]
- how the enthalpy change of the reaction, \(\Delta H\), is represented and its sign [2]
(ii) Explain, in terms of bond breaking and bond making, why this reaction is exothermic. [3]

(b) Use the bond energy values in the table below to calculate the overall enthalpy change for the reaction.

| Bond | Bond Energy (kJ/mol) |
|---|---|
| H-H | 436 |
| Cl-Cl | 243 |
| H-Cl | 431 |

(i) Calculate the energy required to break the bonds in 1 mole of \(\text{H}_2\) and 1 mole of \(\text{Cl}_2\). [1]
(ii) Calculate the energy released when the bonds in 2 moles of \(\text{HCl}\) are formed. [1]
(iii) Calculate the overall enthalpy change, \(\Delta H\), for this reaction. Include the sign and appropriate units. [2.33]

(c) State and explain the change in temperature of the surroundings when an endothermic reaction occurs. [2]

An eco-friendly de-icer contains a mixture of sodium chloride (which is soluble in water) and calcium carbonate (which is insoluble in water, but soluble and reactive with dilute acids).

Plan an investigation to determine the percentage by mass of calcium carbonate in a sample of this de-icer.

You are provided with:
- a sample of the solid de-icer mixture
- distilled water
- standard laboratory apparatus (including balances, burners, and glassware)

Your answer should include:
(a) a detailed method for the experiment [6 marks]
(b) the name of one piece of apparatus used to measure 50 cm³ of water accurately [1 mark]
(c) an explanation of why the residue must be washed with distilled water before drying [1 mark]
(d) how you would prove that all the water has been removed from the dried residue [1 mark]
(e) one safety precaution, other than wearing eye protection, and why it is necessary [1 mark]

A student investigated the rate of reaction between calcium carbonate (marble chips) and dilute hydrochloric acid at room temperature. The equation for the reaction is:
\(\text{CaCO}_3(\text{s}) + 2\text{HCl}(\text{aq}) \rightarrow \text{CaCl}_2(\text{aq}) + \text{H}_2\text{O}(\text{l}) + \text{CO}_2(\text{g})\)

(a) Why does the rate of reaction decrease over time as the reaction proceeds? [1 mark]

(b) The student repeated the experiment using the same mass of calcium carbonate but in the form of a single large marble chip instead of several small marble chips.
(i) Describe and explain how the rate of reaction would change. Use collision theory in your explanation. [2 marks]
(ii) How would the final volume of gas collected compare to the first experiment? Explain your answer. [1 mark]

(c) The reaction was repeated at a higher temperature.
(i) How would the curve of volume of gas against time for this higher temperature compare to the original room temperature experiment? State two differences. [2 marks]
(ii) Explain the effect of higher temperature on the rate of reaction in terms of collision theory. [3 marks]

(d) Suggest why measuring the volume of gas collected in a gas syringe is a more accurate method for carbon dioxide than collecting the gas over water in a graduated cylinder. [1 mark]

Two substances, solid Y and solid Z, were analysed. Solid Y was a green transition metal salt. Solid Z was an anhydrous salt.

The following tests were carried out on both solids. Complete the observations and conclusions.

(a) Tests on Solid Y:
Distilled water was added to solid Y to make a green solution.
(i) To the first portion of solution Y, aqueous sodium hydroxide was added dropwise until in excess.
State the observations. [2 marks]
(ii) The mixture from (i) was then warmed gently. A gas was evolved which turned damp red litmus paper blue.
Identify the gas evolved and the cation responsible for this gas. [2 marks]
(iii) To a second portion of solution Y, dilute nitric acid was added followed by aqueous barium nitrate. A white precipitate was formed.
State the name of the precipitate and identify the anion present in solid Y. [2 marks]

(b) Tests on Solid Z:
A flame test was performed on solid Z. A lilac flame was observed.
Identify the cation present in solid Z. [1 mark]

(c) Solid Z was heated strongly in a hard-glass test-tube.
- A brown gas was evolved.
- A glowing splint relit when held at the mouth of the tube.
(i) Identify the brown gas. [1 mark]
(ii) Identify the gas that relit the glowing splint. [1 mark]
(iii) Use these results to deduce the formula of solid Z. [1 mark]

A student carried out a titration to determine the concentration of a sample of dilute sulfuric acid by titrating it against 25.0 cm³ of standard sodium hydroxide solution, concentration 0.100 mol/dm³.

(a) Name the apparatus used to:
(i) measure exactly 25.0 cm³ of the sodium hydroxide solution into the conical flask. [1 mark]
(ii) deliver variable, accurate volumes of the dilute sulfuric acid during the titration. [1 mark]

(b) Methyl orange indicator was added to the conical flask containing sodium hydroxide. State the colour change observed at the end-point. [2 marks]

(c) The titration was performed three times. The burette readings are shown below:
- Run 1: Initial reading = 0.0 cm³; Final reading = 22.4 cm³
- Run 2: Initial reading = 22.4 cm³; Final reading = 44.2 cm³
- Run 3: Initial reading = 1.5 cm³; Final reading = 23.4 cm³
(i) State the volume of acid added in each of the three runs. [1 mark]
(ii) Identify the anomalous run and explain why it should be excluded from the calculation of the average titre. [2 marks]
(iii) Calculate the average volume of dilute sulfuric acid used using the concordant results. [1 mark]

(d) Suggest why the student placed the conical flask on a white tile. [1 mark]

(e) Explain why rinsing the inside of the conical flask with distilled water during the titration does not affect the accuracy of the result. [1 mark]