AS & A Level Chemistry - 9701 Paper 1 2015 Winter Zone 1

The table gives the successive ionisation energies for an element X.

[Table_1]

What could be the formula of a chloride of X?

Which set of conditions gives the highest yield of ammonia at equilibrium?
$N_2(g) + 3H_2(g) \rightleftharpoons 2NH_3(g) \quad \Delta H^\circ = -92 \, \text{kJ} \, \text{mol}^{-1}$
[Table_1]

Use of the Data Booklet is relevant to this question.
The compound $\text{S}_2\text{O}_7$ is hydrolysed by water to produce sulfuric acid and oxygen only.
Which volume of oxygen, measured at room temperature and pressure, is evolved when 0.352 g of $\text{S}_2\text{O}_7$ is hydrolysed?

Nitrogen, $N_2$, and carbon monoxide, $CO$, both have $M_r = 28$.
The boiling point of $N_2$ is 77K.
The boiling point of $CO$ is 82K.
What could be responsible for this difference in boiling points?

Some car paints contain small flakes of silica, $\text{SiO}_2$.
In the structure of solid $\text{SiO}_2$:
• each silicon atom is bonded to $x$ oxygen atoms,
• each oxygen atom is bonded to $y$ silicon atoms,
• each bond is a $z$ type bond.
What is the correct combination of $x$, $y$ and $z$ in these statements?
[Table_1]

Solid sulfur consists of molecules made up of eight atoms covalently bonded together.
The bonding in sulfur dioxide is O=S=O.

enthalpy change of combustion of $S_8$, $\Delta H_c S_8\text{(s)} = -2376 \text{kJ mol}^{-1}$
energy required to break 1 mole $S_8(\text{s})$ into gaseous atoms = 2232 $\text{kJ mol}^{-1}$
$\text{O}=\text{O}$ bond enthalpy = 496 $\text{kJ mol}^{-1}$

Using these data, what is the value of the S=O bond enthalpy?

Use of the Data Booklet is relevant for this question.
In an experiment, the burning of 1.45 g (0.025 mol) of propanone was used to heat 100 g of water. The initial temperature of the water was 20.0°C and the final temperature of the water was 78.0°C.
Which experimental value for the enthalpy change of combustion for propanone can be calculated from these results?

Which row correctly describes the electrodes that can be used in a diaphragm cell for the production of chlorine, hydrogen and sodium hydroxide? [Table_1]

Hexamine is a crystalline solid used as a fuel in portable stoves. The diagram shows its skeletal structure. What is the empirical formula of hexamine?

A mixture of nitrogen and hydrogen gases, at a temperature of 500K, was put into an evacuated vessel of volume 6.0 dm$^3$. The vessel was then sealed.

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

The mixture was allowed to reach equilibrium. It was found that 7.2 mol of $\text{N}_2$ and 12.0 mol of $\text{H}_2$ were present in the equilibrium mixture. The value of the equilibrium constant, $K_c$, for this equilibrium is $6.0 \times 10^{-2}$ at 500K.

What is the concentration of ammonia present in the equilibrium mixture at 500K?

Ammonia is made by the Haber process. The reactants are nitrogen and hydrogen.
$$\text{N}_2(g) + 3\text{H}_2(g) \rightleftharpoons 2\text{NH}_3(g) \quad \Delta H \text{-ve}$$
What will increase the rate of the forward reaction?

X is a Group II metal. The carbonate of X decomposes when heated in a Bunsen flame to give carbon dioxide and a white solid residue as the only products. This white solid residue is sparingly soluble in water. Even when large amounts of the solid residue are added to water the pH of the saturated solution is less than that of limewater.
What could be the identity of X?

Rat poison needs to be insoluble in rain water but soluble at the low pH of stomach contents.
What is a suitable barium compound to use for rat poison?

Use of the Data Booklet is relevant to this question.
Which of the elements sodium, magnesium, aluminium, silicon, phosphorus, sulfur and chlorine
• has a lower first ionisation energy than the preceding element in the Periodic Table,
• conducts electricity and
• has a lower atomic radius than the preceding element in the Periodic Table?

The melting points of the Period 3 elements sodium to aluminium are shown in the table.

[Table_1]

element     Na     Mg     Al
mp/K        371         923         932

Which factor explains the increase in melting points from sodium to aluminium?

X is the oxide of a Period 3 element. X reacts with water to give an acidic solution. A solution is prepared by reacting 0.100 g of X with excess water. This solution was neutralised by exactly 25.0 cm³ of 0.100 mol dm⁻³ sodium hydroxide solution. What could be the identity of X?

Which statement about bromine is correct?

The addition of aqueous silver nitrate to aqueous barium chloride produces a white precipitate which dissolves in excess dilute aqueous ammonia to form a colourless solution.
The addition of excess dilute nitric acid to the colourless solution produces a white precipitate, $Z$.
What is $Z$?

Element X forms a pollutant oxide Y. Y can be further oxidised to Z. Two students made the following statements:
Student P ‘The molecule of Y contains lone pairs of electrons.’
Student Q ‘The oxidation number of X increases by 1 from Y to Z.’
X could be carbon or nitrogen or sulfur.
Which student(s) made a correct statement?

How many isomeric esters have the molecular formula C_4H_8O_2?

A new jet fuel has been produced that is a mixture of different structural isomers of compound Q.
Which skeletal formula represents a structural isomer of Q?

Crude oil is a mixture of many hydrocarbons ranging in size from 1 to 40 carbon atoms per molecule. The alkanes in crude oil can be separated because they have different boiling points.

The table below shows the boiling points of some alkanes.

[Table_1]

What is the correct explanation for the difference in the boiling points of the three isomers with $M_r = 72$?

Compound Q contains three double bonds per molecule.

Which bond, X or Y, will be ruptured by hot, concentrated acidified KMnO$_4$ and how many lone pairs of electrons are present in one molecule of Q?

Which compound undergoes an $S_N1$ substitution reaction with NaOH(aq)?

If the starting material is iodoethane, which sequence of reactions will produce propanoic acid as the main final product in good yield?

Which compound cannot be oxidised by acidified potassium dichromate(VI) solution but does react with sodium metal?

Butan-2-ol can be made by reducing X with H$_2$/Ni.
Butan-2-ol can be dehydrated to form Y and Z which are structural isomers of each other.
Which row is correct?
[Table_1]

Tollens' reagent can be used to help identify compounds P, Q and R.

[Image_1: Structures of compounds P, Q, and R]

Which compound(s) form a silver precipitate on warming with Tollens' reagent?

Sorbitol is a naturally-occurring compound with a sweet taste. It is often used as a substitute for sucrose by the food industry.

How many chiral centres are present in sorbitol?

Which compound produces butan-2-ol and ethanoic acid on hydrolysis?

Which statements about orbitals in a krypton atom are correct?
1. The 1s and 2s orbitals have the same energy as each other but different sizes.
2. The third energy level (n=3) has three subshells and nine orbitals.
3. The 3d subshell has five orbitals that have the same energy as each other in an isolated atom.

The Group IV elements carbon, silicon and germanium can all exist in the giant molecular structure which is also found in diamond. The bond lengths in these structures are given below.
[Table_1]
Why does the bond length increase down the group?
1 Orbital overlap decreases down the group.
2 Atomic radius increases down the group.
3 Nuclear charge increases down the group.

The salt $\text{NaClO}_3$ is used as a non-selective weedkiller. On careful heating, this reaction occurs: $4\text{NaClO}_3 \to \text{NaCl} + 3\text{NaClO}_4$. On strong heating this reaction occurs: $\text{NaClO}_4 \to \text{NaCl} + 2\text{O}_2$. The overall reaction is $2\text{NaClO}_3 \to 2\text{NaCl} + 3\text{O}_2$. What do these equations show?
1. $\text{NaClO}_3$ can behave as an oxidising agent.
2. $\text{NaClO}_3$ can behave as a reducing agent.
3. The oxidation numbers of chlorine in the three compounds shown are +6, +8 and −1.

Which statements correctly describe an effect of a rise in temperature on a gas-phase reaction?
1. More particles now have energies greater than the activation energy.
2. The energy distribution profile changes with more particles having the most probable energy.
3. The activation energy of the reaction is decreased.

Which statements concerning the Group II elements magnesium, calcium and barium are correct?
1. Their reactivity increases with increasing relative atomic mass.
2. The oxidation number exhibited in their stable compounds is +2.
3. On strong heating, their nitrates give off oxygen only.

Sulfur dioxide is used as a food preservative.
Which statements about sulfur dioxide, SO$_2$, are correct?
1. SO$_2$ behaves as an antioxidant.
2. Aqueous SO$_2$ contains SO$_3^{2-}$ ions.
3. SO$_2$ inhibits the growth of mould and yeasts.

An oxidising agent that can oxidise ethanol to ethanoic acid, or to ethanoate ions, will also oxidise methanoic acid, HCO_2H, to carbon dioxide and water.
Which reagents, on heating, will react differently with HCO_2H and CH_3CO_2H?
1. Na_2CO_3(aq)
2. Fehling’s reagent
3. dilute acidified KMnO_4

Each of the compounds below is treated separately with excess NaBH₄. The product of each reaction is then heated with excess concentrated H₂SO₄.
In each case, one or more products are formed with molecular formula C₇H₁₀.
Which compounds give only one final product with the molecular formula C₇H₁₀?

Which reactions result in the formation of propanoic acid?
1. $\text{CH}_3\text{CH}_2\text{CO}_2\text{Na with dilute H}_2\text{SO}_4\text{(aq)}$
2. $\text{CH}_3\text{CH=CHCH}_3\text{ with hot, concentrated H}^+/\text{MnO}_4^-\text{(aq)}$
3. $\text{CH}_3\text{CH}_2\text{OH with H}^+ /\text{Cr}_2\text{O}_7^{2-}\text{(aq)}$

The diagram shows the structure of propanamide.
Which statements about the hydrolysis of propanamide are correct?
1. Propanamide can be hydrolysed by heating under reflux with $\text{H}_2\text{SO}_4(\text{aq})$.
2. Propanamide can be hydrolysed by heating under reflux with $\text{NaOH}(\text{aq})$.
3. Propanamide can be hydrolysed by cold water.