Chemistry 9701/22 — October/November 2022

Cambridge AS Level · AS Level Structured Questions · worked solutions for every part, with the mark scheme

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Topics Chemical Bonding · Equilibria · Atoms, Molecules and Stoichiometry · Halogen Compounds · Atomic Structure · Nitrogen and Sulfur · +10 more

Q1Chemical BondingAtomic StructureEquilibriaNitrogen and SulfurAtoms, Molecules and StoichiometryHalogen CompoundsFree sample

Species such as $\text{NH}_4^+$ , $\text{CO}_3^{2-}$ and $\text{PO}_4^{3-}$ are examples of molecular ions.

(a)

Ionic and covalent bonds both involve an electrostatic attraction between different species.

Identify the species that are electrostatically attracted to one another in:

an ionic bond

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a covalent bond.

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(b)

Complete Table 1.1 to show the total numbers of protons and electrons in the molecular ions $\text{NH}_4^+$ , $\text{CO}_3^{2-}$ and $\text{PO}_4^{3-}$ .

Table 1.1

molecular ion	total number of protons	total number of electrons
$\text{NH}_4^+$
$\text{CO}_3^{2-}$
$\text{PO}_4^{3-}$

(c)

$\text{NH}_4^+$ is a Brønsted–Lowry acid.

(i)

Define Brønsted–Lowry acid.

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(ii)

When $\text{NH}_4^+(\text{aq})$ is heated with $\text{NaOH}(\text{aq})$ , a pungent gas is produced.

Write an ionic equation for this reaction.

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(iii)

The nitrogen atom in $\text{NH}_4^+$ is $\text{sp}^3$ hybridised. $\text{sp}^3$ orbitals form from the mixing of one 2s and three 2p orbitals.

Sketch the shapes of a 2s and a $2\text{p}_x$ orbital on the axes in Fig. 1.1.

Fig. 1.1

(d)

There are many naturally occurring hydrated compounds that contain the anion $\text{PO}_4^{3-}$ .

(i)

Name the anion $\text{PO}_4^{3-}$ .

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(ii)

Struvite is a soft hydrated mineral with $M_r = 245.3$ . The anhydrous form of the mineral has the formula $\text{NH}_4\text{MgPO}_4$ .

Calculate the number of molecules of water of crystallisation in struvite.

Give your answer to the nearest integer. Show your working.

number of molecules of water of crystallisation = ..............................

(e)

$\text{OH}^-(\text{aq})$ reacts with 2-bromo-2-methylpropane in an $\text{S}_\text{N}1$ reaction.
The molecular ion $(\text{CH}_3)_3\text{C}^+$ forms as the intermediate in this reaction.

(i)

Draw the mechanism for the $\text{S}_\text{N}1$ reaction of $\text{OH}^-$ with 2-bromo-2-methylpropane.
Include charges, dipoles, lone pairs of electrons and curly arrows as appropriate.
Draw the structures of the organic reactant and organic product.

Fig. 1.2

(ii)

2-bromo-2-methylpropane is a tertiary bromoalkane.

Define tertiary bromoalkane.

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(iii)

Organic compound M forms when 2-bromo-2-methylpropane is heated with ethanolic $\text{OH}^-$ .

Draw the structure of M.

The rest of this paper

2 more questions

Q2Chemical Periodicity · Chemical Bonding · Equilibria · States of Matter · Atoms, Molecules and Stoichiometry · Group 1721M
Q3Carbonyl Compounds · Hydrocarbons · Introduction to Organic Chemistry · Polymerisation · Analytical Techniques · Organic Synthesis · Halogen Compounds · Carboxylic Acids and Derivatives22M

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