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

Which contains the largest number of hydrogen atoms?

In which pair of species do both species have only one unpaired p electron?

Phosphorus forms two chlorides. Phosphorus(III) chloride, $\text{PCl}_3$, is a covalent liquid. Phosphorus(V) chloride is an ionic solid. One of the ions present is $[\text{PCl}_4]^+$. What is the shape of the $\text{PCl}_3$ molecule and the $[\text{PCl}_4]^+$ ion? [Table_1]

$\Delta H^\circ_1$ is the standard enthalpy of formation of methane.
$\Delta H^\circ_2$ is the standard enthalpy of combustion of carbon.
$\Delta H^\circ_3$ is the standard enthalpy of combustion of hydrogen.
$$\text{CH}_4(g) + 2\text{O}_2(g) \xrightarrow{\Delta H^\circ_c} \text{CO}_2(g) + 2\text{H}_2\text{O}(l)$$
Which expression is equivalent to $\Delta H^\circ_c$?

The diagram shows the Boltzmann distribution for the same gas at two different temperatures, $T_1$ and $T_2$.

What is plotted on the $y$-axis and which line represents the higher temperature?

What is the minimum mass of oxygen required to ensure the complete combustion of 12 $\text{dm}^3$ of propane measured under room conditions?

Why is the first ionisation energy of oxygen less than that of nitrogen?

Which gas would behave most like an ideal gas under room conditions?

When hydrogen iodide is reacted with concentrated sulfuric acid, several reactions occur, including:
$$8\text{HI} + \text{H}_2\text{SO}_4 \rightarrow \text{H}_2\text{S} + 4\text{H}_2\text{O} + 4\text{I}_2$$
Which row gives the change in oxidation number of iodine and of sulfur in this reaction?
[Table_1]

The diagram represents the Haber process for the manufacture of ammonia from nitrogen and hydrogen. What is the purpose of the heat exchanger?

Which statement about catalysts is correct?

Element X is in Period 3. Element X forms a solid oxide Y.
Y reacts with hot concentrated hydrochloric acid. Y reacts with hot aqueous sodium hydroxide to form a compound in which X is part of an anion.
How many p electrons does one atom of X have in its outer shell?

The gaseous products of heating a mixture of $Ca(OH)_2$ and $NH_4Cl$ are passed through solid $CaO$. A single gaseous product, $W$, is collected.
A sample of $W$ reacts with $Cl_2(g)$ to produce two gases, $X$ and $Y$.
$X$ is an element. $Y$ is acidic.
$Y$ reacts with $W$ to produce $Z$.
What are $X$ and $Z$?
[Table_1]

Q is a mixture of a Group 2 oxide and a Group 2 sulfate. Q contains equal amounts of the two compounds.
Q is shaken with water and the resulting mixture filtered; a solid residue is obtained. There is no reaction when the solid residue is shaken with $HCl(aq)$. Shaking the filtrate with $H_2SO_4(aq)$ produces a white precipitate.
What could be Q?

Which substance will not be a product of the thermal decomposition of hydrated magnesium nitrate?

A 5 cm^3 sample of 0.05 mol dm^{-3} sodium chloride is mixed with a 5 cm^3 sample of 0.05 mol dm^{-3} potassium iodide. 10 cm^3 of acidified 0.05 mol dm^{-3} silver nitrate is then added, followed by concentrated ammonia solution.
What is seen after the addition of an excess of concentrated ammonia solution?

The volatility of the Group 17 elements, chlorine, bromine and iodine, decreases down the group. What is responsible for this trend?

Acid rain is a dilute solution of sulfuric acid. Which pollutant also contributes to the formation of acid rain?

R is an oxide of Period 3 element T. 5.00 g of R contains 2.50 g of T. What is T?

Bromoethane reacts with cyanide ions, producing propanenitrile.
Which statement about the $S_N2$ mechanism of this reaction is correct?

Which compound would produce two different carboxylic acids when treated with hot, concentrated, acidified manganate(VII) ions?

Which compound could show both cis-trans isomerism and optical isomerism?

Limonene is a hydrocarbon found in the rind of citrus fruits.

What is the molecular formula of limonene?

The compound cetyl palmitate, $C_{15}H_{31}CO_2C_{16}H_{33}$, is a waxy solid.
Cetyl palmitate is heated under reflux with an excess of aqueous sodium hydroxide.
Which products will be formed?

When an organic compound is oxidised, any oxygen atom gained by the organic molecule is considered to be from a water molecule also producing $2H^+ + 2e^-$. Any hydrogen atom lost may be considered to be lost as $H^+ + e^-$.
These changes can be represented by the following two equations.
$$ ext{H}_2 ext{O} ightarrow [O] + 2 ext{H}^+ + 2 ext{e}^-$$ $$[ ext{H}] ightarrow ext{H}^+ + ext{e}^-$$
Compound X is oxidised by heating under reflux with hot, acidified potassium dichromate(VI) for one hour. The half-equation for the reduction reaction is shown.
$$ ext{Cr}_2 ext{O}_7^{2-} + 14 ext{H}^+ + 6 ext{e}^- ightarrow 2 ext{Cr}^{3+} + 7 ext{H}_2 ext{O}$$
Under these conditions, one mole of potassium dichromate(VI) oxidises three moles of X. What could X be?

Compound X has the empirical formula C_2H_4O. Its infra-red spectrum is shown.

What could be the skeletal formula of compound X?

How many moles of hydrogen, H$_2$, are evolved when an excess of sodium metal is added to one mole of citric acid?

Which statement is correct for the reaction of carbonyl compounds with HCN?

The table describes four reactions of propene.
Which row is correct?

[Table_1:
| | reagent used | name of main organic product |
|---|-----------------------------------------|-----------------------------|
| A | aqueous bromine | 2-bromopropane |
| B | cold acidified aqueous potassium manganate(VII) | propane-1,3-diol |
| C | hydrogen chloride | 2-chloropropane |
| D | steam | propan-1-ol |
]

Butanoic acid is prepared from 1-bromopropane.
This synthesis requires a sequence of two reactions.
Which compound is prepared in the first stage of the synthesis?

Ethanol combines with ethanoic acid to form ethyl ethanoate according to the following reaction.
$$\text{C}_2\text{H}_5\text{OH}(l) + \text{CH}_3\text{CO}_2\text{H}(l) \rightleftharpoons \text{CH}_3\text{CO}_2\text{C}_2\text{H}_5(l) + \text{H}_2\text{O}(l) \quad \Delta H^\circ = -6 \text{kJ mol}^{-1}$$
9.2 g ethanol, 12 g ethanoic acid and 8.8 g ethyl ethanoate are mixed and allowed to stand at 298 K, until equilibrium is reached.
($$M_r: \text{C}_2\text{H}_5\text{OH}, 46; \text{CH}_3\text{CO}_2\text{H}, 60; \text{CH}_3\text{CO}_2\text{C}_2\text{H}_5, 88$$)
The resulting equilibrium mixture is found to contain 4.8 g ethanoic acid.
The experiment is repeated at 323 K.

Which statements are correct?
1 There are 0.22 moles of ethyl ethanoate in the mixture at equilibrium at 298 K.
2 The equilibrium mixture at 323 K will contain more than 4.8 g of ethanoic acid.
3 If a small amount of water is added at the start of either experiment the value of $$K_c$$ would not be affected.

The diagram shows an incomplete energy profile diagram for a reaction.



Which reactions could this diagram refer to?
1. \( \text{CaCO}_3(s) \rightarrow \text{CaO}(s) + \text{CO}_2(g) \)
2. \( \text{H}_2(g) \rightarrow 2\text{H}(g) \)
3. \( \text{Cl}^-(aq) \rightarrow \text{Cl}^\cdot(g) + \text{aq} \)

A gaseous hydrocarbon has a density of 2.42 g dm$^{-3}$ under room conditions.
What could be the skeletal formula of this hydrocarbon?
[Image_1: Numbered skeletal formulas shown]

Which molecules contain at least one bond angle of 120°?
1. $\text{C}_2\text{H}_4$
2. $\text{PF}_5$
3. $\text{NCl}_3$

Which statements are correct going across Period 3 from sodium to chlorine?
1. The charge on the nucleus increases, pulling the electrons closer to it.
2. The radius of the most common ion of each element decreases.
3. The shielding caused by inner electrons decreases, so the outer electrons are pulled closer to the nucleus.

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.
Which statements are correct?
1. Magnesium carbonate decomposes at a lower temperature than calcium carbonate.
2. Calcium hydroxide is more soluble in water than magnesium hydroxide.
3. Calcium is a stronger reducing agent than magnesium.

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.
Which statements are correct?
1. 1,1-difluoroethane is less reactive than 1,1-dichloroethane.
2. 1,1-difluoroethane is polar.
3. The C–F bond is stronger than the C–Cl bond.

Which pairs of compounds may be distinguished by testing with alkaline aqueous iodine?
1. butanal and butanone
2. pentan-2-one and pentan-3-ol
3. propanone and propan-2-ol

Which reactions have a coloured organic product?
1. ethanal + 2,4-dinitrophenylhydrazine reagent
2. ethanol + acidified potassium dichromate(VI)
3. ethene + cold dilute acidified potassium manganate(VII)

Proponoic acid is reacted with an excess of lithium aluminium hydride. The organic product of this reaction is reacted with ethanoic acid in the presence of concentrated sulfuric acid, forming product X.
What are major commercial uses of X?
1. fuel
2. solvent
3. flavouring