AS & A Level Chemistry - 9701 Paper 1 2021 Summer Zone 3

Compound X is an organic compound that contains 30.6% carbon, 3.8% hydrogen, 20.4% oxygen and 45.2% chlorine by mass.
What is the empirical formula of X?

A sample of propane, $C_3H_8$, with a mass of 9.61 g is completely combusted in an excess of oxygen under room conditions.
Which volume of carbon dioxide gas is produced?

Which atom has the same number of electrons as an ammonium ion?

Ethanol reacts with hydroxylamine, NH$_2$OH, to form the molecule shown.
What is the order of extbf{increasing} bond angle in this structure from smallest to largest?

Descriptions of the bonding in three substances are given.

substance 1: strong covalent bonds between atoms, permanent dipole-dipole attractions between molecules
substance 2: strong covalent bonds between atoms, weak forces between molecules
substance 3: strong covalent bonds between atoms, hydrogen bonding between molecules

Which compounds could be substances 1, 2 and 3?
[Table_1]

Which type of bonding is \textit{never} found in elements?

Using the information in the table, what is the enthalpy change, $q$, for the reaction described?
$\text{Cs}^{+}(g) + \text{Br}^{-}(g) \rightarrow \text{CsBr}(s) \quad \Delta H = q\text{ kJ mol}^{-1}$
[Table_1]

Which enthalpy change is indicated by X in the enthalpy cycle shown?

Copper dissolves in dilute nitric acid producing a blue solution of Cu(NO_3)_2, water and nitrogen(II) oxide as the only products. How many moles of acid react with three moles of copper in the balanced equation?

Nitrogen reacts with hydrogen to produce ammonia.

$N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g)$

A mixture of 2.00 mol of nitrogen, 6.00 mol of hydrogen and 2.40 mol of ammonia is allowed to reach equilibrium in a sealed vessel of volume 1 dm$^3$. It is found that 2.32 mol of nitrogen were present in the equilibrium mixture.

Which expression will give the value of $K_c$?

Nitric acid is produced by oxidising ammonia. The first step is to react ammonia with oxygen in the presence of a catalyst to form nitrogen monoxide.
$$4\text{NH}_3(g) + 5\text{O}_2(g) \rightleftharpoons 4\text{NO}(g) + 6\text{H}_2\text{O}(g) \quad \Delta H = -1636\, \text{kJ mol}^{-1}$$
Which set of conditions will produce the greatest yield of nitrogen monoxide at equilibrium?
[Table_1]

The height of the peak of the curve in a Boltzmann distribution represents the number of molecules that have the most probable energy. A sample of gas has its temperature decreased without changing the number of molecules present. Which statement correctly describes a feature of the Boltzmann distribution for the gas when the temperature decreases?

Ammonia exists as simple covalent molecules, $\text{NH}_3$. Ammonia can react with suitable reagents to form products containing ammonium ions, $\text{NH}_4^+$. Ammonia can also react with suitable reagents to form products containing amide ions, $\text{NH}_2^-$.
Which of these nitrogen-containing species are present in an aqueous solution of ammonia?

Which problem can result if too much $\text{NH}_4\text{NO}_3$ is applied to crops by farmers?

When descending Group 17 from chlorine to iodine, which statement is correct?

A powder is known to be either a single sodium halide or a mixture of two sodium halides. A sample of the powder was dissolved in water.
Aqueous silver nitrate was added, and a pale yellow precipitate was formed. When concentrated aqueous ammonia was then added, this precipitate partly dissolved leaving a darker yellow precipitate.
What could the powder be?

Which statement is correct?

A solid, X, was placed in an excess of the liquid Y. A colourless gas was given off and a white precipitate was seen. The precipitate was not X. What could be the identities of X and Y? [Table_1]

Two oxides of Period 3 elements are added separately to water. Both react to form colourless solutions. One solution is alkaline, the other is acidic.
What could be the two oxides?

Which compound shows stereoisomerism?

Two carbon-containing products result from the reaction of alkene Z with a hot, concentrated, acidified solution of potassium manganate(VII).
One product forms an orange precipitate with 2,4-dinitrophenylhydrazine reagent. The other product is a gas which gives a white precipitate with aqueous calcium hydroxide.
Which alkene could be alkene Z?

What is the correct mechanism for the addition of hydrogen bromide to ethene?

Halogenoalkanes react with nucleophiles such as OH^-.
Which pair of halogenoalkanes both react via an S_N1 mechanism?

A mixture of ethanol and methanol is burned in oxygen to produce 35 cm³ of CO₂ and 55 cm³ of H₂O.
Complete combustion occurs and the volumes of both products are measured at 101 kPa and 120°C.
What is the molar ratio, ethanol:methanol, in the mixture?

Two reactions are shown. Only one product is identified in each reaction.
ethanol + acidified $\text{Cr}_2\text{O}_7^{2-} \rightarrow$ ethanal
ethanol + sodium $\rightarrow$ sodium ethoxide
Which statement about these reactions is correct?

The skeletal formulae of three compounds are shown.
[Image_1: Compounds R, S, T]
Which compounds will give a positive test with 2,4-dinitrophenylhydrazine reagent?

The diagram shows the structure of a compound formed by the reaction of HCN with a carbonyl compound, X.

What is the mechanism of this reaction and what is the functional group in X?
[Table_1]

Compound Y is treated with a single reagent under suitable conditions. 2-methylbutanoic acid is produced.
What could compound Y be?

Two reactions are shown.

$$(CH_3)_2CHCO_2H \xrightarrow{LiAlH_4} \text{alcohol P}$$
$$CH_3CO_2CH(CH_3)_2 \xrightarrow{\text{hydrolysis}} \text{alcohol Q} + \text{acid R}$$

To which classes of alcohol do P and Q belong?

[Table_1]

The infra-red spectrum of molecule Z is shown. What could be the identity of Z?

Which statements about first ionisation energies are correct?
1. They are always endothermic.
2. They decrease down Group 2.
3. They decrease across Period 3.

The equation shows the decomposition of three moles of an ion containing chromium in an acid solution.
$$3\text{CrO}_4^{3-}(aq) + 8\text{H}^+(aq) \rightarrow 2\text{CrO}_4^{2-}(aq) + \text{Cr}^{3+}(aq) + 4\text{H}_2\text{O}(l)$$
Which statements are correct?
1. One mole of CrO$_4^{3-}$ is reduced.
2. Two moles of CrO$_4^{3-}$ are oxidised.
3. Three moles of electrons are transferred.

Disaccharides are hydrolysed in slightly acidic solutions. This reaction is very slow.
A biological catalyst is added to a slightly acidic mixture of three disaccharides, sucrose, maltose and lactose. The hydrolysis reaction remains slow for sucrose and maltose but is now much faster for lactose.
Which statements about the catalyst are correct?

1. The catalyst increases the activation energy of all three hydrolysis reactions.
2. The catalyst shows specificity.
3. The hydrolysis of lactose using a catalyst has a different mechanism to the hydrolysis of lactose without a catalyst.

Element X is a solid under room conditions. It occurs as a contaminant of fossil fuels.
Its oxide, Y, is formed when fossil fuels are burned.
In the atmosphere, Y can be further oxidised to Z.
Which statements about X, Y and Z are correct?
1. Atoms of X have paired p electrons.
2. The atmospheric oxidation of Y to Z is a catalysed reaction.
3. With water, Z forms a strong acid.

Which reagents produce a solution of sodium chlorate(V)?
1. chlorine and hot concentrated sodium hydroxide solution
2. chlorine and cold dilute sodium hydroxide solution
3. chlorine dissolved in water at room temperature

Which statements help to explain the increase in melting point from sodium to aluminium?
1. The charge on the metal ion increases.
2. There are more delocalised electrons per metal ion.
3. The radius of the metal ion decreases.

The diagram shows a molecule of a compound used as a flame retardant.

Which statements about this structure are correct?
1. Each brominated C atom is chiral.
2. The molecular formula is $C_{12}H_{20}Br_{6}$.
3. The C–C–C bond angles are all 120°.

Bromoethane reacts with NaOH in different ways depending on the solvent used.
Which rows about these reactions are correct?
[Table_1]

The responses A to D should be selected on the basis of

[Table_1]

No other combination of statements is used as a correct response.

Three compounds, X, Y and Z, are shown.

X \[ \text{C}_2\text{H}_5\text{COCH}_3 \]
Y \[ \text{C}_2\text{H}_5\text{CHO} \]
Z \[ \text{CH}_3\text{CO}_2\text{H} \]

Which statements about X, Y and Z are correct?

1 X reacts with alkaline aqueous iodine.
2 Y reacts with Tollens’ reagent.
3 Z does not react with alkaline aqueous iodine.

5-hydroxypentanoic acid is readily converted into the cyclic compound L. Which statements about this reaction are correct?
1 Acidified sodium dichromate(VI) is used as a reagent.
2 A water molecule is produced in the reaction.
3 The reaction can be catalysed by concentrated H$_2$SO$_4$.