Oct/Nov 2025

What is the electron arrangement for the particle $^{{27}}_{{13}}\mathrm{Al}^{+}$?

1.1

Which equation demonstrates hydrogen behaving as an oxidising agent?

4.1

$1.00\,\mathrm{g}$ of nitrogen gas is contained in a $2.00\,\mathrm{dm^3}$ vessel at $40.0^\circ\mathrm{C}$. What pressure is in the vessel?

1.1

A single molecule of haemoglobin, Hb, is able to combine with four molecules of oxygen, as represented by the equation below. $\mathrm{Hb(aq) + 4O_2(aq) \rightleftharpoons Hb(O_2)_4(aq)}$. If the equilibrium concentration of $\mathrm{O_2}$ is $7.6 \times 10^{-6}\,\mathrm{mol\,dm^{-3}}$, and the equilibrium concentrations of Hb and $\mathrm{Hb(O_2)_4}$ are the same, determine the numerical value of $K_c$ for this equilibrium.

2.4

Aqueous acid P and aqueous alkali Q have equal concentrations. $20\text{ cm}^3$ of P is placed into a conical flask. Q is then added slowly to the flask, and the volume of Q together with the pH are noted. The pH titration curve is shown. Which row shows the identities of P and Q?

8.2

Photochromic glass, which is used for sunglasses, turns darker when it is exposed to strong light and becomes more transparent again when the light is weaker. This darkening happens because silver atoms are present in the glass. The reactions below are involved. reaction 1 is: $\mathrm{Ag^+ + Cl^- \rightleftharpoons Ag + Cl}$ reaction 2 is: $\mathrm{Cu^+ + Cl \rightarrow Cu^{2+} + Cl^-}$ reaction 3 is: $\mathrm{Cu^{2+} + Ag \rightarrow Cu^+ + Ag^+}$ Which statement correctly describes these reactions?

3.2

A small volume of concentrated sulfuric acid is added to catalyse the reversible reaction between liquid methanol and liquid ethanoic acid. Two claims about this reaction are given below. 1. The sulfuric acid acts as a homogeneous catalyst. 2. The sulfuric acid reduces the activation energy for the reverse reaction. Which claims are correct?

6.1

The atomic radii and ionic radii of three elements in Period 3 are given below. Element X: atomic radius $0.118\text{ nm}$, ionic radius $0.053\text{ nm}$ Element Y: atomic radius $0.099\text{ nm}$, ionic radius $0.180\text{ nm}$ Element Z: atomic radius $0.160\text{ nm}$, ionic radius $0.072\text{ nm}$ From these data, which statement is correct?

1.1

Three equations are given below. $x$, $y$ and $z$ are all whole numbers. 1. $x\mathrm{Al} + y\mathrm{O_2} \rightarrow z\mathrm{Al_2O_3}$ 2. $x\mathrm{Mg} + y\mathrm{O_2} \rightarrow z\mathrm{MgO}$ 3. $x\mathrm{Na} + y\mathrm{O_2} \rightarrow z\mathrm{Na_2O}$ For which equations is it possible to balance them when $x=4$ and $z=2$?

1.1

Which oxide has a simple structure instead of a giant structure?

2.1

The patterns observed in Group 2 can be used to forecast the properties of radium and its compounds. Which of the following statements is correct?

3.1

The table shows the 5th to the 10th ionisation energies of three elements from Period 3 of the Periodic Table. Which three elements are they?

2.1

Equal masses of $\mathrm{CaCO_3}$, $\mathrm{Ca(NO_3)_2}$, $\mathrm{BaCO_3}$ and $\mathrm{Ba(NO_3)_2}$ are heated until they thermally decompose. The gas volume from each experiment is then measured under identical conditions. Which compound will produce the largest volume of gas?

3.1

Equation 1 and equation 2 illustrate two distinct reactions involving the halide ion $\mathrm{Q^-}$ and concentrated sulfuric acid. Equation 1: $\mathrm{H_2SO_4 + Q^- \rightarrow HSO_4^- + HQ}$ Equation 2: $\mathrm{H_2SO_4 + 2Q^- + 2H^+ \rightarrow SO_2 + Q_2 + 2H_2O}$ Identify Q.

8.1

What is observed when iodine solution is added to a sodium bromide solution?

3.1

Which of the following statements is correct?

1.1

When dry ammonia gas and hydrogen chloride gas are brought together, a white solid ionic compound is produced. Two statements are given below. 1. The production of the ionic compound is a redox reaction. 2. As the ionic compound forms, the H-N-H bond angle becomes larger. Which statements are correct?

2.1

The diagrams illustrate skeletal formulas for some isomers of $\mathrm{C_6H_{12}O}$. Which statement is true?

3.2

The skeletal formulae of two compounds are shown (progesterone and testosterone). Which of the following statements about progesterone and testosterone are correct?

2.1

During the addition of HBr to propene, which intermediate ion is formed in the largest amount?

6.1

Two hydrocarbons, $\mathrm{R{-}CH_3}$ and $\mathrm{R'{-}CH_3}$, each react on their own with bromine when ultraviolet light is present. Among these hydrocarbons, one is unsaturated. In both cases, free radical substitution occurs. $\mathrm{R}$ is $\mathrm{CH_3CHC(CH_3)}$. $\mathrm{R'}$ is $\mathrm{CH_3CH(CH_3)CH_2}$. Which row gives the correct answer?

4.1

Exhaust fumes from cars that burn petrol contain the pollutants below. By oxidation inside a catalytic converter, which of these pollutants are removed?

10.2

Which substance contains $9.03 \times 10^{23}$ oxygen atoms?

1.1

Compound X, $\mathrm{C_7H_{11}ICl_2}$, is dissolved in ethanol and the resulting solution is then combined with warm aqueous silver nitrate. A precipitate forms at once. State the colour of this precipitate and give the structural formula of the first organic product.

6.1

After $\mathrm{1,4}$-dibromobutane is treated with excess ethanolic sodium hydroxide and no more reaction occurs, what is the relative formula mass of the principal organic product?

4.3

A short segment of a polymer formed from two monomers is shown: $\mathrm{-CH_2-C(CH_3)_2-CH(CH_3)-CH_2-}$. Which two monomers formed it?

3.4

The balanced equation for the reaction of X with an excess of acidified $\mathrm{K_2Cr_2O_7}$ is given below. $\mathrm{X + 3[O] \rightarrow Y + H_2O}$. Compound Y is the only organic product formed in the reaction. Which compound is X?

8.3

Three mixtures are heated under reflux. Which of these mixtures would give sodium propanoate as one product?

6.3

Which compound is formed as a result of the hydrolysis of $\text{CH}_3\text{CO}_2\text{CH}_2\text{C}_2\text{H}_5$ with aqueous sodium hydroxide?

8.3

When heated with HCN in the presence of a catalyst, compound Q reacts to form compound R. Each molecule of compound R contains four carbon atoms. What is compound Q?

4.2

The table lists the reactants and products for three reactions. 1. $\text{ethanoic acid} + \text{Na}_2\text{CO}_3 \rightarrow \text{CH}_3\text{CO}_2\text{Na} + \text{H}_2\text{O} + \text{CO}_2$ 2. $\text{ethanoic acid} + \text{Mg} \rightarrow (\text{CH}_3\text{CO}_2)_2\text{Mg} + \text{H}_2\text{O}$ 3. $\text{ethanoic acid} + \text{CH}_3\text{OH} \rightarrow \text{CH}_3\text{CO}_2\text{CH}_3 + \text{H}_2\text{O}$ Which of the rows are correct?

8.2

There are seven aldehydes and ketones • each molecule contains only one oxygen atom • their structures include four or fewer carbon atoms. Alkaline $\text{I}_2(\text{aq})$ is then introduced separately to each carbonyl compound. For how many of these carbonyl compounds is a yellow precipitate formed with alkaline $\text{I}_2(\text{aq})$?

8.2

Several characteristics of compound X are given below. • $1.0\,\text{mol}$ X burns completely in exactly $8.5\,\text{mol}$ oxygen. • X shows no reaction when it is heated with acidified $\text{KMnO}_4$. What are the possible identities of X?

4.1

Methane reacts with steam to make hydrogen. $\mathrm{CH_4(g) + 2H_2O(g) \rightarrow CO_2(g) + 4H_2(g)}$ . $0.80\,\mathrm{g}$ of methane and $1.35\,\mathrm{g}$ of steam react. One reactant is completely consumed. What volume of hydrogen, measured at room conditions, will be formed?

1.1

In a magnesium sample, the only isotopes present are $^{24}\text{Mg}$, $^{25}\text{Mg}$ and $^{26}\text{Mg}$. The percentage abundance of $^{25}\text{Mg}$ and $^{26}\text{Mg}$ is equal. The relative atomic mass of magnesium in the sample is 24.3. What is the percentage abundance of $^{24}\text{Mg}$?

1.1

Which statement accounts for the different melting points of sodium and potassium?

3.1

$\mathrm{NH_3}$ and HCN combine to produce $\mathrm{NH_4CN}$, which is an ionic compound. Which row gives the number of coordinate bonds and the number of $\pi$ bonds present in one formula unit of $\mathrm{NH_4CN}$?

2.1

If $1.0\,\mathrm{mol}$ of ethanoic acid, $\mathrm{CH_3COOH}$, in aqueous solution undergoes neutralisation with excess aqueous sodium hydroxide, $55\,\mathrm{kJ\,mol^{-1}}$ of energy is given out. Which statement about this reaction is correct?

5.1

During an experiment, $1.60\,\mathrm{g}$ of a fuel is burned. Of the energy given out, $45.0\%$ is taken in by $200\,\mathrm{g}$ of water. The water’s temperature increases from $18.0^\circ\mathrm{C}$ to $66.0^\circ\mathrm{C}$. What is the total energy released per gram of fuel burnt?

1.1

Sulfite ions, $\mathrm{SO_3^{2-}}$, react independently with zinc and with manganese dioxide. $a$, $b$, $c$, $d$, $w$, $x$, $y$ and $z$ are all whole numbers. $a\mathrm{SO_3^{2-}(aq)} + b\mathrm{H_2O(l)} + \mathrm{Zn(s)} \rightarrow \mathrm{Zn^{2+}(aq)} + c\mathrm{OH^{-}(aq)} + d\mathrm{S_2O_4^{2-}(aq)}$ and $\mathrm{MnO_2(s)} + w\mathrm{SO_3^{2-}(aq)} + x\mathrm{H^{+}(aq)} \rightarrow \mathrm{Mn^{2+}(aq)} + y\mathrm{S_2O_6^{2-}(aq)} + z\mathrm{H_2O(l)}$. Which values of $a$, $b$, $w$ and $x$ are correct?

6.1

What would the electrons in boxes notation for the $\mathrm{Fe}^{3+}$ ion be?

1.1

A commercially sold ‘heat pad’ includes iron, activated carbon and water. When air activates the ‘heat pad’, its temperature rises. Which statement describes the chemical reaction taking place in the ‘heat pad’ when it is exposed to air?

5.1

In which substance is the average oxidation number of sulfur greatest?

2.1

An equilibrium may be described by the equation below. $P(\mathrm{aq}) + Q(\mathrm{aq}) \rightleftharpoons 2R(\mathrm{aq}) + S(\mathrm{aq})$ For one mixture with a volume of $1.0\,\mathrm{dm}^3$, the equilibrium concentration of Q is $10\,\mathrm{mol\,dm}^{-3}$. Determine the new equilibrium concentration of Q after $5.0\,\mathrm{mol}$ of pure Q has been completely dissolved into the mixture.

4.1

In the Contact process, sulfur dioxide reacts with oxygen to produce sulfur trioxide. In the Haber process, nitrogen reacts with hydrogen to produce ammonia. Which statement about these processes is correct?

8.1

$20.0\,\mathrm{cm}^3$ of hydrogen peroxide breaks down into water and oxygen in the presence of a suitable catalyst. After $5.00$ minutes, $160\,\mathrm{cm}^3$ of oxygen, measured at room conditions, has been formed. What is the average rate of decomposition of hydrogen peroxide over this reaction period?

1.1

Which reaction pathway diagram represents an endothermic reaction carried out in two steps, with the second step likely to proceed more quickly than the first?

4.1

Oxides of nitrogen, $\mathrm{NO}_x$, are involved in the formation of photochemical smog and acid rain. Which oxides of nitrogen take part in each of these processes?

10.3

Sodium and sulfur react to produce sodium sulfide, $\mathrm{Na}_2\mathrm{S}$. In what way do the atomic radius and ionic radius of sodium differ from those of sulfur?

2.1

Compound X is an oxide of a Period 3 element. At $25^{\circ}\mathrm{C}$, compound X is a white solid. When it reacts with water, an acidic solution is formed. What is compound X?

3.1

When magnesium nitrate is heated, it decomposes. Which equation correctly represents the thermal decomposition of magnesium nitrate?

4.1

Which equation shows an energy change equal to the first ionisation energy of bromine?

3.1

R is a water solution of an ionic compound. When R is mixed with $\mathrm{Sr(NO_3)_2(aq)}$, a white precipitate appears. If R is mixed with dilute $\mathrm{HNO_3(aq)}$, no visible change occurs. What anion is present in compound R?

8.1

During an experiment, $0.600\,\mathrm{mol}$ of chlorine gas, $\mathrm{Cl_2}$, reacts with an excess of hot aqueous sodium hydroxide. One product formed is $\mathrm{NaClO_3}$. What mass of $\mathrm{NaClO_3}$ is produced?

1.1

X and Y are sodium salts of Group 17 elements. If X is treated with concentrated sulfuric acid, hydrogen sulfide, $\mathrm{H_2S}$, is formed. If Y is treated with concentrated sulfuric acid, the oxidation number of sulfur does not alter. Which statement is correct?

3.2

Element E lies in Period 3. It makes a chloride that, when a little water is added, gives a white precipitate together with steamy fumes. This precipitate dissolves in $\mathrm{NaOH(aq)}$ and in $\mathrm{HCl(aq)}$. What is element E?

3.1

Four reaction mixtures are given. 1. $(\text{NH}_4)_2\text{SO}_4\text{(aq)}$ together with $\text{NaOH}$ 2. $\text{NH}_4\text{Cl(aq)}$ together with $\text{Ba(OH)}_2$ 3. $\text{NH}_4\text{Cl(aq)}$ together with $\text{Na}_2\text{O}$ 4. $(\text{NH}_4)_3\text{PO}_4\text{(aq)}$ together with $\text{HCl}$ Which of these reaction mixtures gives ammonia as a product?

8.1

Two statements about a methanal molecule are given. 1. It is planar. 2. It has three $\sigma$ bonds. Which of these statements is correct?

1.2

The displayed structure of disodium cromoglycate is shown. How many chiral centres does this molecule contain?

5.1

What is the main product formed when 2-methylpent-2-ene reacts with hydrogen bromide?

5.1

Pent-2-ene is treated with cold, dilute, acidified manganate(VII) ions. Which is the major product formed?

8.2

Limonene is an oil made in the peel of citrus fruits. Which product is produced when limonene reacts with an excess of bromine, $\text{Br}_2\text{(l)}$, at room temperature in the dark?

4.2

Hydrogen sulfide reacts with sulfur dioxide to form sulfur as one of the products. The two relevant redox equations are given below. $\mathrm{H_2S}(aq) \rightleftharpoons \mathrm{S}(s) + 2\mathrm{H}^{+}(aq) + 2e^{-}$ $\mathrm{SO_2}(aq) + 4\mathrm{H}^{+}(aq) + 4e^{-} \rightleftharpoons \mathrm{S}(s) + 2\mathrm{H_2O}(l)$ How many moles of hydrogen sulfide are required to react with sulfur dioxide and produce 1 mol of sulfur?

4.1

Which reaction mixture forms a nitrile?

8.2

Which reaction falls under the classification $\text{S}_\text{N}1$?

9.3

Which reaction mixture gives a primary alcohol as the main product?

10.2

If $\text{HOCH}_2\text{CHO}$ is heated under reflux with an excess of acidified $\text{K}_2\text{Cr}_2\text{O}_7$ until no further change occurs, what final product is formed in this reaction?

6.1

An organometallic lithium compound, $\text{RLi}$, contains the nucleophile $\text{R}^-$. $\text{CH}_3\text{CH}_2\text{Li}$ undergoes reaction with pentan-2-one. This reaction proceeds by nucleophilic addition. During the first step, an anion is generated, and this is then protonated to give the final product. What organic product is produced?

4.3

The displayed structure of a naturally occurring compound, Q, is shown below. Compound Q is heated under reflux with an excess of acidified $\text{KMnO}_4$. The organic product R is produced. Which row is the correct one?

6.2

Which organic starting material could be used in one reaction to make propanoic acid?

4.1

During four distinct reactions, W, X, Y and Z, 1 mol of an organic compound reacts with an excess amount of a reagent. Reaction table: - W: organic compound $(\text{CH}_2\text{COOH})_2$, reagent $\text{Na}$ - X: organic compound $\text{CH}_3\text{CH(OH)CH}_2\text{COOH}$, reagent $\text{Na}_2\text{CO}_3$ - Y: organic compound $\text{CH}_3\text{CH(OH)CH}_2\text{COOH}$, reagent $\text{NaOH}$ - Z: organic compound $\text{CH(OH)(COOH)CH}_2\text{COOH}$, reagent $\text{Na}$ Any gas formed is gathered and its volume is measured. All gas volumes are recorded at the same temperature and pressure. What is the sequence of the reactions from the largest total volume of gas collected to the smallest total volume of gas collected?

8.3

Butylamine may be prepared by reacting butanenitrile with hydrogen in the presence of a suitable catalyst. What volume of hydrogen, at room conditions, is needed to react completely with 0.500 g of butanenitrile?

2.8

A fragment of an addition polymer is shown. Which monomer was used to produce this polymer?

4.8

Which one of the following statements is correct?

0.0

Infrared spectroscopy can be used to assess how pure a compound is. The table lists the characteristic infrared absorption frequencies of several selected bonds. Propan-2-ol is produced by the hydration of propene, and a sample of the product is collected. Which part of the infrared spectrum of the product would indicate that none of the propene is still present?

2.2

In an $\mathrm{N_2}$ molecule, the bond between the two nitrogen atoms is formed by the hybridisation of atomic orbitals to produce sp orbitals. Which row is correct?

2.1

Three bond angles are marked on the molecule shown. What is the descending order of the bond angles $x$, $y$ and $z$, from largest to smallest?

1.1

X and Y are two different elements in Period 3. In the atoms of X and Y, each has just one fully occupied orbital in the highest occupied energy sub-shell. Y has a higher first ionisation energy than X. Which row correctly shows the structure and bonding of X and Y?

2.1

A gas in a pure sample has a density of $2.62\,\text{g dm}^{-3}$ at $101000\,\text{Pa}$ and $25^{\circ}\text{C}$. Under these conditions, the gas obeys the ideal gas model. Which formula gives the $M_r$ of the gas?

1.1

When $0.47\,\text{g}$ of a hydrocarbon is burned completely in air, the energy given out raises the temperature of $200\,\text{g}$ of water from $23.7^{\circ}\text{C}$ up to $41.0^{\circ}\text{C}$. Calculate the amount of energy absorbed, in Joules, by the water?

3.1

What electronic configuration corresponds to the particle $^{{27}}_{{13}}\mathrm{Al}^{+}$?

1.1

Which equation demonstrates hydrogen behaving as an oxidising agent?

4.1

$1.00\,\mathrm{g}$ of nitrogen gas is kept in a $2.00\,\mathrm{dm^3}$ vessel at $40.0\,^{\circ}\mathrm{C}$. Calculate the pressure in the vessel.

1.1

A single molecule of haemoglobin, Hb, is able to combine with four molecules of oxygen, as shown by the equation below. $\mathrm{Hb(aq) + 4O_2(aq) \rightleftharpoons Hb(O_2)_4(aq)}$ At equilibrium, when the concentration of $\mathrm{O_2}$ is $7.6 \times 10^{-6}\,\mathrm{mol\,dm^{-3}}$, the equilibrium concentrations of Hb and $\mathrm{Hb(O_2)_4}$ are the same. Calculate the numerical value of $K_c$ for this equilibrium.

3.2

Aqueous acid P and aqueous alkali Q have identical concentrations. $20\,\text{cm}^3$ of P is placed in a conical flask. Q is then added gradually to the flask, and the volume of Q together with the pH is measured. The pH titration curve is shown. Which row identifies P and Q?

8.2

Photochromic glass, which is used for sunglasses, becomes darker when it is exposed to bright light and then returns to being more transparent when the light is weaker. The darkening of the glass is caused by the presence of silver atoms. The reactions below are involved. Reaction 1: $\text{Ag}^+ + \text{Cl}^- \rightleftharpoons \text{Ag} + \text{Cl}$. Reaction 2: $\text{Cu}^+ + \text{Cl} \rightarrow \text{Cu}^{2+} + \text{Cl}^-$. Reaction 3: $\text{Cu}^{2+} + \text{Ag} \rightarrow \text{Cu}^+ + \text{Ag}^+$. Which statement about these reactions is correct?

8.1

A small amount of concentrated sulfuric acid is added to catalyse the reversible reaction between methanol and ethanoic acid liquids. Two claims about this reaction are given. 1. The sulfuric acid is a homogeneous catalyst. 2. The sulfuric acid reduces the activation energy of the reverse reaction. Which claims are correct?

4.1

The atomic radii and ionic radii for three Period 3 elements are given below. For element X, the atomic radius is $0.118\,\text{nm}$ and the ionic radius is $0.053\,\text{nm}$. For element Y, the atomic radius is $0.099\,\text{nm}$ and the ionic radius is $0.180\,\text{nm}$. For element Z, the atomic radius is $0.160\,\text{nm}$ and the ionic radius is $0.072\,\text{nm}$. On the basis of this data, which statement is correct?

1.1

Three equations are shown. $x$, $y$ and $z$ are all whole numbers. 1. $x\text{Al} + y\text{O}_2 \rightarrow z\text{Al}_2\text{O}_3$ 2. $x\text{Mg} + y\text{O}_2 \rightarrow z\text{MgO}$ 3. $x\text{Na} + y\text{O}_2 \rightarrow z\text{Na}_2\text{O}$ Which of these equations could be balanced when $x=4$ and $z=2$?

2.1

Which oxide has a simple structure rather than a giant one?

1.1

The patterns observed in Group 2 can be used to forecast the properties of radium and its compounds. Which statement is correct?

3.1

The table shows the 5th to the 10th ionisation energies for three Period 3 elements in the Periodic Table. Which three elements are correctly identified?

1.1

When equal masses of $\text{CaCO}_3$, $\text{Ca(NO}_3\text{)}_2$, $\text{BaCO}_3$ and $\text{Ba(NO}_3\text{)}_2$ are heated so that thermal decomposition takes place, the volume of gas formed in each experiment is measured under the same conditions. Which compound will give the largest volume of gas?

3.2

Equation 1 and equation 2 illustrate two separate reactions between halide ion Q$^-$ and concentrated sulfuric acid. Equation 1: $\text{H}_2\text{SO}_4 + \text{Q}^- \rightarrow \text{HSO}_4^- + \text{HQ}$. Equation 2: $\text{H}_2\text{SO}_4 + 2\text{Q}^- + 2\text{H}^+ \rightarrow \text{SO}_2 + \text{Q}_2 + 2\text{H}_2\text{O}$. Which halide ion is Q?

4.1

What occurs when iodine solution is added to a solution of sodium bromide?

3.1

Which statement is the correct one?

X.Y

A solid white ionic compound is produced when dry ammonia gas and hydrogen chloride gas are brought together. Two statements are given. 1. The making of the ionic compound is a redox reaction. 2. As the ionic compound forms, the H-N-H bond angle becomes larger. Which statements are correct?

2.1

The diagrams illustrate skeletal formulas of some isomers of $\text{C}_6\text{H}_{12}\text{O}$. Which statement is correct?

2.4

Skeletal formulae for two compounds are shown: progesterone and testosterone. Which statements concerning progesterone and testosterone are correct?

4.2

During the addition of HBr to propene, which intermediate ion is formed in the largest amount?

4.3

Two hydrocarbons, $\text{R-CH}_3$ and $\text{R'-CH}_3$, react separately with bromine in the presence of ultraviolet light. Of these two hydrocarbons, one is unsaturated. In each reaction, free radical substitution takes place. $\text{R}$ is $\text{CH}_3\text{CHC(CH}_3)$ . $\text{R'}$ is $\text{CH}_3\text{CH(CH}_3)\text{CH}_2$ . Which row gives the correct answer?

4.1

The exhaust fumes from petrol-fuelled cars contain the pollutants listed below. Which pollutants are removed by oxidation in a catalytic converter?

3.4

Which substance contains $9.03 \times 10^{23}$ oxygen atoms?

1.1

Compound X, $\text{C}_7\text{H}_{11}\text{ICl}_2$, is dissolved in ethanol, then the solution is combined with warm aqueous silver nitrate. A precipitate appears at once. What colour is this precipitate, and what is the structural formula of the first organic product?

6.1

$1,4$-dibromobutane is treated with an excess of ethanolic sodium hydroxide until the reaction stops completely. What is the relative formula mass of the main organic product?

4.3

A short segment of a polymer formed from two monomers is shown as, $-\text{CH}_2-\text{C(CH}_3)_2-\text{CH(CH}_3)-\text{CH}_2-$. Which two monomers were used to make it?

4.2

The balanced equation for the reaction of X with an excess of acidified potassium dichromate(VI) is given. $\text{X} + 3[\text{O}] \rightarrow \text{Y} + \text{H}_2\text{O}$. Compound Y is the sole organic product formed in the reaction. Which compound is X?

6.2

Three reaction mixtures are heated under reflux. Which of them will yield sodium propanoate as one of the products?

8.4

Which compound is formed when $\text{CH}_3\text{CO}_2\text{CH}_2\text{C}_2\text{H}_5$ is hydrolysed with aqueous sodium hydroxide?

8.3

On heating with HCN and in the presence of a catalyst, compound Q undergoes reaction to form compound R. Each molecule of compound R has four carbon atoms. Identify compound Q.

4.2

The table lists the reagents and products for three reactions. 1. $\text{ethanoic acid} + \text{Na}_2\text{CO}_3 \rightarrow \text{CH}_3\text{CO}_2\text{Na} + \text{H}_2\text{O} + \text{CO}_2$ 2. $\text{ethanoic acid} + \text{Mg} \rightarrow (\text{CH}_3\text{CO}_2)_2\text{Mg} + \text{H}_2\text{O}$ 3. $\text{ethanoic acid} + \text{CH}_3\text{OH} \rightarrow \text{CH}_3\text{CO}_2\text{CH}_3 + \text{H}_2\text{O}$ Which of the rows are correct?

8.1

Seven aldehydes and ketones • Each molecule has just one oxygen atom. • Each structure contains no more than four carbon atoms. The seven carbonyl compounds are tested one by one with alkaline $\text{I}_2\text{(aq)}$. For how many of these carbonyl compounds is a yellow precipitate formed with alkaline $\text{I}_2\text{(aq)}$?

8.3

Several characteristics of compound X are given below. • $1.0\,\text{mol}$ X reacts with exactly $8.5\,\text{mol}$ oxygen when it is fully combusted. • X shows no reaction when warmed with acidified $\text{KMnO}_4$. What could X possibly be?

4.2

Methane reacts with steam to make hydrogen. $\mathrm{CH_4(g) + 2H_2O(g) \rightarrow CO_2(g) + 4H_2(g)}$ $0.80\,\mathrm{g}$ of methane and $1.35\,\mathrm{g}$ of steam are allowed to react. One of the reactants is completely consumed. What volume of hydrogen will be formed, measured at room conditions?

2.1

A sample of magnesium contains only the isotopes $^{24}\text{Mg}$, $^{25}\text{Mg}$ and $^{26}\text{Mg}$. The percentage abundance of $^{25}\text{Mg}$ and $^{26}\text{Mg}$ is equal. The relative atomic mass of magnesium in the sample is $24.3$. Calculate the percentage abundance of $^{24}\text{Mg}$.

1.1

Which statement accounts for the different melting points of sodium and potassium?

2.1

$\mathrm{NH_3}$ and HCN combine to make $\mathrm{NH_4CN}$, which is an ionic compound. Which row gives the number of coordinate bonds and the number of $\pi$ bonds in one formula unit of $\mathrm{NH_4CN}$?

2.1

If $1.0\,\mathrm{mol}$ of ethanoic acid, $\mathrm{CH_3COOH}$, in aqueous solution is neutralised using an excess of aqueous sodium hydroxide, $55\,\mathrm{kJ\,mol^{-1}}$ of energy is given out. Which statement about this reaction is correct?

5.2

In an experiment, $1.60\,\mathrm{g}$ of a fuel is burnt. $45.0\%$ of the energy given out is absorbed by $200\,\mathrm{g}$ of water. The temperature of the water increases from $18.0\,^{\circ}\mathrm{C}$ to $66.0\,^{\circ}\mathrm{C}$. What is the total energy released per gram of fuel burnt?

1.1

The sulfite ions, $\mathrm{SO_3^{2-}}$, react individually with zinc and with manganese dioxide. $a$, $b$, $c$, $d$, $w$, $x$, $y$ and $z$ each represent whole numbers. $a\mathrm{SO_3^{2-}(aq)} + b\mathrm{H_2O(l)} + \mathrm{Zn(s)} \rightarrow \mathrm{Zn^{2+}(aq)} + c\mathrm{OH^{-}(aq)} + d\mathrm{S_2O_4^{2-}(aq)}$ $\mathrm{MnO_2(s)} + w\mathrm{SO_3^{2-}(aq)} + x\mathrm{H^{+}(aq)} \rightarrow \mathrm{Mn^{2+}(aq)} + y\mathrm{S_2O_6^{2-}(aq)} + z\mathrm{H_2O(l)}$ Which values are correct for $a$, $b$, $w$ and $x$?

8.2