(a)

$10 \mathrm{~cm}^{3}$ of a gaseous hydrocarbon, $\mathrm{C}_{x} \mathrm{H}_{y}$ , was reacted with $100 \mathrm{~cm}^{3}$ of oxygen gas, an excess. The final volume of the gaseous mixture was $95 \mathrm{~cm}^{3}$ .

This gaseous mixture was treated with concentrated, aqueous sodium hydroxide to absorb the carbon dioxide present. This reduced the gas volume to $75 \mathrm{~cm}^{3}$ .

All gas volumes were measured at 298 K and 100 kPa .

[ 1 ]

(i)

Write an equation for the reaction between sodium hydroxide and carbon dioxide.

[ 1 ]

[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 ]

[Maximum number: 9]

Methanoic acid, $\mathrm{HCO}_{2} \mathrm{H}$ , was formerly known as formic acid because it is present in the sting of ants and the Latin name for ant is formica. It was first isolated in 1671 by John Ray who collected a large number of dead ants and extracted the acid from them by distillation.

In this question, you should give all numerical answers to two significant figures.
At room temperature, pure methanoic acid is a liquid which is completely soluble in water.
When we are stung by a 'typical' ant a solution of methanoic acid, A, is injected into our skin.

Solution A contains 50\% by volume of pure methanoic acid.
A 'typical' ant contains $7.5 \times 10^{-6} \mathrm{dm}^{3}$ of solution A.

(a)

(i)

Construct a balanced equation for the reaction between methanoic acid and sodium hydrogencarbonate.

[Maximum number: 4]

Compound A is an organic compound which contains carbon, hydrogen and oxygen.
When 0.240 g of the vapour of A is slowly passed over a large quantity of heated copper(II) oxide, CuO , the organic compound A is completely oxidised to carbon dioxide and water. Copper is the only other product of the reaction.

The products are collected and it is found that 0.352 g of $\mathrm{CO}_{2}$ and 0.144 g of $\mathrm{H}_{2} \mathrm{O}$ are formed.

(a)

Use your answers to (a) to calculate the empirical formula of A.

[ 1 ]

(b)

When a 0.148 g sample of A was vapourised at $60^{\circ} \mathrm{C}$ , the vapour occupied a volume of $67.7 \mathrm{~cm}^{3}$ at a pressure of 101 kPa .

[ 3 ]

(i)

Hence calculate the molecular formula of A.

[ 3 ]

[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: 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 ]

(a)

Calcium nitrate, $\mathrm{Ca}\left(\mathrm{NO}_{3}\right)_{2}$ , is used in fertilisers and can be prepared by an acid-base reaction. Write an equation for the preparation of calcium nitrate by an acid-base reaction.

[ 1 ]

[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 ]

(a)

Magnesium can be produced by electrolysis of magnesium chloride in a molten mixture of salts.

[ 2 ]

(i)

An investigation of the reaction between magnesium oxide and hydrogen chloride gas showed that an intermediate product was formed with the composition by mass $\mathrm{Mg}, 31.65 \% ; \mathrm{O}, 20.84 \% ; \mathrm{H}, 1.31 \%$ and Cl, 46.20 %.

Calculate the empirical formula of this intermediate compound.
empirical formula

[ 2 ]

(a)

The element tellurium, Te, reacts with chlorine to form a single solid product, with a relative formula mass of 270. The product contains 52.6\% chlorine by mass.

[ 3 ]

(i)

Calculate the molecular formula of this chloride.
molecular formula

[ 3 ]