AS & A Level Chemistry - 9701 Paper 2 2012 Winter Zone 3

Carbon dioxide, $\text{CO}_2$, makes up about 0.040\% of the Earth’s atmosphere. It is produced by animal respiration and by the combustion of fossil fuels.
In animal respiration, oxygen reacts with a carbohydrate such as glucose to give water, carbon dioxide and energy.
The typical daily food requirement of a human can be considered to be the equivalent of 1.20 kg of glucose, $\text{C}_6\text{H}_{12}\text{O}_6$.
You should express all of your numerical answers in this question to \textbf{three} significant figures.
(a) (i) Construct a balanced equation for the complete oxidation of glucose.
(ii) Use your equation to calculate the amount, in moles, of $\text{CO}_2$ produced by one person in one day from 1.20 kg of glucose.
(iii) On the day on which this question was written, the World population was estimated to be $6.82 \times 10^9$.
Calculate the total mass of $\text{CO}_2$ produced by this number of people in one day. Give your answer in tonnes. [1 tonne = $1.00 \times 10^6$ g].

(b) When fossil fuels are burned in order to give energy, carbon dioxide and water are also produced.
The hydrocarbon octane, $\text{C}_8\text{H}_{18}$, can be used to represent the fuel burned in motor cars. A typical fuel-efficient motor car uses about 4.00 dm$^3$ of fuel to travel 100 km.
(i) Construct a balanced equation for the complete combustion of octane.
(ii) The density of octane is 0.700 g cm$^{-3}$.
Calculate the amount, in moles, of octane present in 4.00 dm$^3$ of octane.
(iii) Calculate the mass of $\text{CO}_2$ produced when the fuel-efficient car is driven for a distance of 100 km.

(c) Calculate how many kilometres the same fuel-efficient car would have to travel in order to produce as much $\text{CO}_2$ as is produced by the respiration of $6.82 \times 10^9$ people during one day. Use your answer to (a)(iii).

(d) Carbon dioxide is one of a number of gases that are responsible for global warming. When fossil fuels such as octane are burned in a car engine, other atmospheric pollutants are also produced.
Give the formula of \textbf{one} atmospheric pollutant that may be produced in a car engine, other than $\text{CO}_2$, and state how this pollutant damages the environment.
pollutant .................................
damage caused ...........................................................

(a) (i) What will be seen when concentrated sulfuric acid is carefully added to solid sodium chloride?
.........................................................................................................................................................................
(ii) Write a balanced equation for this reaction.
.........................................................................................................................................................................
(iii) Solutions of both $H_2SO_4$ and $HCl$ are strong acids.
What is meant by the term strong acid?
.........................................................................................................................................................................
[3]

(b) If the same reaction is carried out with solid sodium iodide and concentrated sulfuric acid, hydrogen iodide is not produced.
(i) State one observation you would make when carrying out this reaction with solid sodium iodide.
.........................................................................................................................................................................
(ii) Explain why hydrogen iodide is not a product of this reaction.
.........................................................................................................................................................................
[3]

(c) Aqueous silver nitrate and aqueous ammonia are used to test for the presence of halide ions.
(i) Aqueous silver nitrate is slowly added to aqueous sodium chloride and the resulting mixture is then shaken with an excess of aqueous ammonia.
Describe what you would observe at each stage of this process.
.........................................................................................................................................................................
(ii) Write balanced equations, with state symbols, for all reactions that occur in this process.
.........................................................................................................................................................................
(iii) The same process of adding aqueous silver nitrate followed by an excess of aqueous ammonia is repeated using aqueous sodium iodide instead of aqueous sodium chloride.
State two differences that would be observed with aqueous sodium iodide.
.........................................................................................................................................................................
[8]

(a) State one large scale use of hydrogen in the chemical industry.
......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [1]

One common way of producing hydrogen on a large scale for use in the chemical industry is by the steam 'reforming' of methane (natural gas), in which steam and methane are passed over a catalyst at 1000–1400 K to produce carbon monoxide and hydrogen.
$$ ext{CH}_4( ext{g}) + ext{H}_2 ext{O}( ext{g}) \rightleftharpoons ext{CO}( ext{g}) + 3 ext{H}_2( ext{g}) \quad \Delta H = +206 \text{kJ} \text{mol}^{-1}$$

(b) Use the information above to state and explain the effect on the equilibrium position of the following changes.

(i) increasing the pressure applied to the equilibrium
......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [2]

(ii) decreasing the temperature of the equilibrium
......................................................................................................................... ......................................................................................................................... ......................................................................................................................... [4]

(c) What will be the effect on the rate of the reaction of increasing the pressure at which it is carried out? Explain your answer.
......................................................................................................................... ......................................................................................................................... .......................................................................................................................... .......................................................................................................................... [2]

(d) Further hydrogen can be obtained by the 'water-gas shift' reaction in which the carbon monoxide produced is reacted with steam.
$$ ext{CO}( ext{g}) + ext{H}_2 ext{O}( ext{g}) \rightleftharpoons ext{CO}_2( ext{g}) + ext{H}_2( ext{g}) \quad K_c = 6.40 \times 10^{-1} \text{ at } 1100 \text{ K}$$
A mixture containing 0.40 mol of CO, 0.40 mol of H$_2$O, 0.20 mol of CO$_2$ and 0.20 mol of H$_2$ was placed in a 1 dm$^3$ flask and allowed to come to equilibrium at 1100 K.

(i) Give an expression for $K_c$ for this reaction.
......................................................................................................................... .......................................................................................................................... [2]

(ii) Calculate the amount, in moles, of each substance present in the equilibrium mixture at 1100 K.

$$\begin{array}{cccc}\text{CO(g)} & + & \text{H}_2\text{O(g)} & \rightleftharpoons & \text{CO}_2\text{(g)} & + & \text{H}_2\text{(g)} \\ \hline \text{initial moles} & 0.40 & 0.40 & 0.20 & 0.20 \\ \end{array}$$
......................................................................................................................... ......................................................................................................................... [3]

Many organic compounds, including alcohols, carbonyl compounds, carboxylic acids and esters, contain oxygen.

(a) The table below lists some oxygen-containing organic compounds and some common laboratory reagents.
(i) Complete the table as fully as you can.
If you think no reaction occurs, write 'no reaction' in the box for the structural formula(e).

[Table_1]

The molecular formula $C_4H_8O$ can represent a number of compounds which have different functional groups and which show different types of isomerism. Compounds $H$, $J$ and $K$ each have the molecular formula $C_4H_8O$. In each of the molecules of $H$, $J$ and $K$,
• the carbon chain is unbranched and the molecule is not cyclic,
• no oxygen atom is attached to any carbon atom which is involved in π bonding.

When compound $H$ is reacted with sodium metal, a colourless flammable gas is produced.

Both $J$ and $K$ give an orange-red precipitate when reacted with 2,4-dinitrophenylhydrazine reagent but only $K$ reacts with Fehling’s solution.

(a) (i) Suggest possible structural formulae for $H$, $J$ and $K$.
Three structural formulae are possible for $H$ but only one for $J$ and one for $K$.

[Table_1]

In addition to being structural isomers of each other, some of the possible structures for $H$, $J$ or $K$ show extit{cis-trans} isomerism or are chiral.

(ii) Draw the displayed formulae of those isomers which show extit{cis-trans} isomerism.

(iii) Draw the displayed formulae of those isomers which are chiral, indicating in each case the chiral carbon atom with an asterisk (*).