[Maximum number: 5]

Sulfuric acid is manufactured by the Contact process.
One stage in this process is the conversion of sulfur dioxide into sulfur trioxide in the presence of a heterogeneous catalyst of vanadium(V) oxide, $\mathrm{V}_{2} \mathrm{O}_{5}$ .

(a)

The $\mathrm{SO}_{3}$ produced is converted to sulfuric acid in two stages. In the first stage the $\mathrm{SO}_{3}$ is reacted with concentrated sulfuric acid to produce oleum, $\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{7}$ .
The oleum is then reacted with water to form sulfuric acid.
Suggest an equation for the reaction of oleum, $\mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{7}$ , with water to form sulfuric acid.

[ 1 ]

(b)

$\mathrm{SO}_{2}$ reacts with water to form sulfurous acid.

Sulfurous acid is a weak Brønsted-Lowry acid, while sulfuric acid is a strong Brønsted-Lowry acid.

[ 4 ]

(i)

State the meaning of the term strong Brønsted-Lowry acid.

[ 2 ]

(ii)

Write an equation to show the acid-base behaviour of sulfuric acid with water. Include state symbols.

[ 2 ]

[Maximum number: 3]

The elements phosphorus, sulfur and chlorine are in Period 3 of the Periodic Table.

Table 1.1 shows some properties of the elements P to Cl .
The first ionisation energy of S is not shown.

Table 1.1

(a)

A student does three tests on separate samples of NaCl(aq).

Complete Table 1.2 with the observations the student makes in each test.

Table 1.2

[ 3 ]

[Maximum number: 3]

Sulfides are compounds that contain sulfur but not oxygen.

(a)

Hydrogen sulfide gas, $\mathrm{H}_{2} \mathrm{~S}(\mathrm{~g})$ , is slightly soluble in water. It acts as a weak acid in aqueous solution.

[ 1 ]

(i)

State the meaning of weak acid.

[ 1 ]

(b)

The compound $\mathrm{As}_{2} \mathrm{~S}_{3}$ is a common mineral.

When $\mathrm{As}_{2} \mathrm{~S}_{3}$ is heated strongly in air, it forms a mixture of products, as shown.

2 \mathrm{As}_{2} \mathrm{~S}_{3}(\mathrm{~s})+9 \mathrm{O}_{2}(\mathrm{~g}) \rightarrow \mathrm{As}_{4} \mathrm{O}_{6}(\mathrm{~s})+6 \mathrm{SO}_{2}(\mathrm{~g})

[ 2 ]

(i)

$\quad \mathrm{SO}_{2}(\mathrm{~g})$ can be removed from the air by reacting it with NaOH(aq).

Construct an equation for the reaction of $\mathrm{SO}_{2}(\mathrm{~g})$ with NaOH(aq). Include state symbols.

[ 2 ]

[Maximum number: 11]

In 1814, Sir Humphrey Davy and Michael Faraday collected samples of a flammable gas, A, from the ground near Florence in Italy.
They analysed A which they found to be a hydrocarbon. Further experiments were then carried out to determine the molecular formula of A.

(a)

When $10 \mathrm{~cm}^{3}$ of A was mixed at room temperature with $50 \mathrm{~cm}^{3}$ of oxygen (an excess) and exploded, $40 \mathrm{~cm}^{3}$ of gas remained after cooling the apparatus to room temperature and pressure.
When this $40 \mathrm{~cm}^{3}$ of gas was shaken with an excess of aqueous potassium hydroxide, $\mathrm{KOH}, 30 \mathrm{~cm}^{3}$ of gas still remained.

[ 4 ]

(i)

The combustion of A produced a gas that reacted with the KOH(aq).

What is the identity of this gas?

[Maximum number: 2]

Sodium oxide, $\mathrm{Na}_{2} \mathrm{O}$ , is a white crystalline solid with a high melting point.

(a)

When sodium oxide reacts with water an alkaline solution is obtained.

[ 2 ]

(i)

Explain why the solution obtained is alkaline. You should use the Brønsted-Lowry theory of acids and bases in your answer.

[ 2 ]

[Maximum number: 3]

Silicon tetrachloride, $\mathrm{SiCl}_{4}$ , is formed when silicon reacts with chlorine under suitable conditions. It is a colourless liquid with a low boiling point.

(a)

$\mathrm{SiCl}_{4}$ reacts with water to produce an acidic solution.

[ 3 ]

(i)

A sample of 0.8505 g of $\mathrm{SiCl}_{4}$ is added to $800 \mathrm{~cm}^{3}$ of water. All of the soluble acidic product is dissolved in the water.

Calculate the pH of the solution obtained.

\mathrm{pH}=

[ 3 ]

[Maximum number: 2]

Species such as $\mathrm{NH}_{4}{ }^{+}, \mathrm{CO}_{3}{ }^{2-}$ and $\mathrm{PO}_{4}{ }^{3-}$ are examples of molecular ions.

(a)

$\mathrm{NH}_{4}{ }^{+}$ is a Brønsted-Lowry acid.

[ 2 ]

(i)

Define Brønsted-Lowry acid.

[ 1 ]

(ii)

When $\mathrm{NH}_{4}{ }^{+}(\mathrm{aq})$ is heated with NaOH(aq), a pungent gas is produced.

Write an ionic equation for this reaction.

[ 1 ]

[Maximum number: 2]

Hydrogen iodide, HI, is a colourless gas at room temperature.

(a)

In the laboratory, HI(aq) can be formed in a two-step process.

step $13 \mathrm{I}_{2}(\mathrm{~s})+2 \mathrm{P}(\mathrm{s}) \rightarrow 2 \mathrm{PI}_{3}(\mathrm{~s})$

step $2 \mathrm{PI}_{3}(\mathrm{~s})+3 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{H}_{3} \mathrm{PO}_{3}(\mathrm{aq})+3 \mathrm{HI}(\mathrm{aq})$

[ 2 ]

(i)

$\quad \mathrm{H}_{3} \mathrm{PO}_{3}(\mathrm{aq})$ and HI(aq) are both strong Brønsted-Lowry acids.

Give the meaning of the term strong Brønsted-Lowry acid.

[ 2 ]

[Maximum number: 3]

Copper is a transition element and has atomic number 29.

(a)

Ethane-1,2-diamine is a useful reagent in organic chemistry.

[ 3 ]

(i)

Explain how the amino groups in ethane-1,2-diamine allow the molecule to act as a Brønsted-Lowry base.

[ 2 ]

(ii)

Write an equation for the reaction of ethane-1,2-diamine with an excess of hydrochloric acid.

[ 1 ]

(a)

The iron(II) complex ferrous bisglycinate hydrochloride is sometimes prescribed, in capsule form, to treat iron deficiency or anaemia.
A capsule containing 500 mg of this iron(II) complex was dissolved in dilute $\mathrm{H}_{2} \mathrm{SO}_{4}$ and titrated with $0.0200 \mathrm{~mol} \mathrm{dm}^{-3} \mathrm{KMnO}_{4}$ .
$18.1 \mathrm{~cm}^{3}$ of $\mathrm{KMnO}_{4}$ solution were required to reach the end point.
The equation for the titration reaction is as follows.

5 \mathrm{Fe}^{2+}+\mathrm{MnO}_{4}^{-}+8 \mathrm{H}^{+} \rightarrow 5 \mathrm{Fe}^{3+}+\mathrm{Mn}^{2+}+4 \mathrm{H}_{2} \mathrm{O}

(i)

Describe how you would recognise the end point of this titration.