[Maximum number: 7]

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)

What is meant by the term molecular formula?

Davy and Faraday deduced the formula of A by exploding it with an excess of oxygen and analysing the products of combustion.

[ 2 ]

(b)

Complete and balance the following equation for the complete combustion of a hydrocarbon with the formula $\mathrm{C}_{x} \mathrm{H}_{y}$ .

\mathrm{C}_{x} \mathrm{H}_{y}+\left(x+\frac{y}{4}\right) \mathrm{O}_{2} \rightarrow

+

[ 2 ]

(c)

Use your equation in (b) and your results from (c)(iii) and (c)(iv) to calculate the molecular formula of A. Show all of your working.

[ 3 ]

[Maximum number: 3]

Aluminium is a metal in Period 3 and Group III of the Periodic Table.

(a)

Aluminium reacts with chlorine to form a white, solid chloride that contains 79.7 % chlorine and sublimes (changes straight from a solid to a gas) at $180^{\circ} \mathrm{C}$ .

[ 3 ]

(i)

Calculate the empirical formula of the chloride. You must show your working.
empirical formula =

At $200^{\circ} \mathrm{C}$ and 100 kPa , a 1.36 g sample of this chloride occupied a volume of $200 \mathrm{~cm}^{3}$ .

[ 2 ]

(ii)

Deduce the molecular formula of this chloride at $200^{\circ} \mathrm{C}$ .

[ 1 ]

[Maximum number: 1]

A0.17 g sample of a Group 14 chloride, $\mathrm{XCl}_{4}$ , reacted with water to produce an oxide, $\mathrm{XO}_{2}$ , and HCl.
equation 1

\mathrm{XCl}_{4}(\mathrm{~s})+2 \mathrm{H}_{2} \mathrm{O}(\mathrm{l}) \rightarrow \mathrm{XO}_{2}(\mathrm{~s})+4 \mathrm{HCl}(\mathrm{aq})

The HC lproduced was absorbed in $100 \mathrm{~cm}^{3}$ of $0.10 \mathrm{~mol} \mathrm{dm}^{-3}$ sodium hydroxide solution (an excess).
In a titration, the unreacted sodium hydroxide solution required $30.0 \mathrm{~cm}^{3}$ of $0.20 \mathrm{~mol} \mathrm{dm}^{-3}$ hydrochloric acid for complete neutralisation.

(a)

Write the equation for the reaction between hydrochloric acid and sodium hydroxide.

[ 1 ]

[Maximum number: 1]

Combustion data can be used to calculate the empirical formula, molecular formula and relative molecular mass of many organic compounds.

(a)

T is an alcohol, $\mathrm{C}_{x} \mathrm{H}_{y} \mathrm{O}$ . A gaseous sample of T occupied a volume of $20 \mathrm{~cm}^{3}$ at $120^{\circ} \mathrm{C}$ and 100 kPa .

The sample was completely burned in $200 \mathrm{~cm}^{3}$ of oxygen (an excess). The final volume, measured under the same conditions as the gaseous sample, was $250 \mathrm{~cm}^{3}$ .

Under these conditions, all water present is vaporised. Removal of the water vapour from the gaseous mixture decreased the volume to $170 \mathrm{~cm}^{3}$ .

Treating the remaining gaseous mixture with concentrated alkali, to absorb carbon dioxide, decreased the volume to $110 \mathrm{~cm}^{3}$ .

The equation for the complete combustion of T can be represented as shown.

\mathrm{C}_{x} \mathrm{H}_{y} \mathrm{O}+z \mathrm{O}_{2} \rightarrow x \mathrm{CO}_{2}+\frac{y}{2} \mathrm{H}_{2} \mathrm{O}

[ 1 ]

(i)

Use the data given to calculate the value of x.

x=

[ 1 ]

(ii)

Use the data given to calculate the value of y.

y=

If you were unable to calculate values for x and y then use x=4 and y=10 for the remaining parts of this question. These are not the correct values.

[Maximum number: 2]

The composition of atoms and ions can be determined from knowledge of atomic number, nucleon number and charge.

(a)

Complete the table.

[ 2 ]

[Maximum number: 2]

Combustion data can be used to calculate the empirical formula, molecular formula and relative molecular mass of many organic compounds. Combustion data cannot distinguish between different structural isomers.

(a)

P is a hydrocarbon, $\mathrm{C}_{x} \mathrm{H}_{y^{\prime}}$ . A gaseous sample of P occupied a volume of $25 \mathrm{~cm}^{3}$ at $37^{\circ} \mathrm{C}$ and 100 kPa .

The sample was completely burned in $200 \mathrm{~cm}^{3}$ of oxygen (an excess).
The final volume, measured under the same conditions as the gaseous sample (so that the water produced is liquid and its volume can be ignored), was $150 \mathrm{~cm}^{3}$ .

Treating the remaining gaseous mixture with concentrated alkali, to absorb carbon dioxide, decreased the volume to $50 \mathrm{~cm}^{3}$ .

The equation for the complete combustion of P can be represented as shown.

\mathrm{C}_{x} \mathrm{H}_{y}+\left(x+\frac{y}{4}\right) \mathrm{O}_{2} \rightarrow x \mathrm{CO}_{2}+\frac{y}{2} \mathrm{H}_{2} \mathrm{O}

[ 2 ]

(i)

Give the molecular formula and the empirical formula of P.
molecular formula of P
empirical formula of P

[ 2 ]

[Maximum number: 5]

The element magnesium, Mg, proton number 12, is a metal which is used in many alloys which are strong and light.

Magnesium has several naturally occurring isotopes.

(a)

(i)

Use your answers to (i) and (ii) to determine the empirical formula of A.

(ii)

The empirical and molecular formulae of A are the same.

Construct a balanced equation for the reaction between antimony and chlorine.

[ 5 ]

[Maximum number: 1]

A Group 2 metal combines with bromine to form a crystalline solid, $\mathrm{MBr}_{2}$ .
Excess aqueous $\mathrm{AgNO}_{3}$ is added to a solution of $\mathrm{MBr}_{2}$ and a precipitate forms. The mixture is filtered. The precipitate is dried and the mass of the precipitate is recorded.

(a)

Complete the equation to represent the reaction between $\mathrm{MBr}_{2}$ and $\mathrm{AgNO}_{3}$ .

[ 1 ]

[Maximum number: 4]

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

(a)

There are many naturally occurring hydrated compounds that contain the anion $\mathrm{PO}_{4}{ }^{3-}$ .

[ 4 ]

(i)

Name the anion $\mathrm{PO}_{4}{ }^{3-}$ .

[ 1 ]

(ii)

Struvite is a soft hydrated mineral with $M_{\mathrm{r}}=245.3$ . The anhydrous form of the mineral has the formula $\mathrm{NH}_{4} \mathrm{MgPO}_{4}$ .

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 =

[ 3 ]

[Maximum number: 1]

A0.50 g sample of a Group 2 metal, M, was added to $40.0 \mathrm{~cm}^{3}$ of $1.00 \mathrm{~mol} \mathrm{dm}^{-3}$ hydrochloric acid (an excess).
equation 1

\mathbf{M}(\mathrm{s})+2 \mathrm{HCl}(\mathrm{aq}) \rightarrow \mathbf{M C l}_{2}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g})

(a)

When the reaction had finished, the resulting solution was made up to $100 \mathrm{~cm}^{3}$ in a volumetric flask.

A $10.0 \mathrm{~cm}^{3}$ sample of the solution from the volumetric flask required $15.0 \mathrm{~cm}^{3}$ of $0.050 \mathrm{moldm}^{-3}$ sodium carbonate solution, $\mathrm{Na}_{2} \mathrm{CO}_{3}$ , for complete neutralisation of the remaining hydrochloric acid.

[ 1 ]

(i)

Write the equation for the complete reaction of sodium carbonate with hydrochloric acid.

[ 1 ]

Question 1

Question 1(a)

Question 1(b)

Question 1(d)

Question 1

Question 1(c)

Question 1(c)(ii)

Question 1(c)(iv)

Question 1

Question 1(b)

Question 1

Question 1(b)

Question 1(b)(i)

Question 1(b)(ii)

Question 1

Question 1(a)

Question 1

Question 1(b)

Question 1(b)(iii)

Question 1

Question 1(e)

Question 1(e)(iii)

Question 1(e)(iv)

Question 1

Question 1(b)

Question 1

Question 1(d)

Question 1(d)(i)

Question 1(d)(ii)

Question 1

Question 1(b)

Question 1(b)(i)