Question
(a) Ethanol can be manufactured by two different methods.
Method 1: fermentation of a sugar, $\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6$
$
\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6 \rightarrow 2 \mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}+2 \mathrm{CO}_2
$
Method 2: reaction of ethene with steam
$
\mathrm{C}_2 \mathrm{H}_4+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}
$
(i) Give one advantage of using fermentation compared with Method 2.[1]
(ii) Give one disadvantage of using fermentation compared with Method 2.[1]
(b) Ethanol reacts with acidified potassium manganate(VII) to form water and a product that turns litmus red.
(i) State the name of the product that turns the litmus red.[1]
(ii) State the type of reaction that ethanol undergoes when it reacts with acidified potassium manganate(VII).[1]
(c) Ethanol reacts with methanoic acid to form an ester.
(i) Name the ester formed in this reaction. ……………………………………………………………………………………………………………………… [1]
(ii) Draw the structure of the ester formed.
Show all of the atoms and all of the bonds.
(d) The table shows the melting points of ethanol and sodium chloride.
The difference in melting points is due to differences in attractive forces between particles in these substances.
Name the type of attractive force in each substance, which is responsible for the difference in melting points.
ethanol ………………………………………………………………………………………………………………………
sodium chloride ………………………………………………………………………………………………………….[2] [Total: 8]
▶️Answer/Explanation
Ans:
7(a)(i) sugar or $\mathrm{C}_6 \mathrm{H}_{12} \mathrm{O}_6$, is renewable/ sustainable
7(a)(ii) slow(er) process
7(b)(i) ethanoic acid
7(b)(ii) oxidation
7(c)(i) ethyl methanoate
7(c)(ii)
7(d) ethanol: (forces of attraction) between molecules (1)
sodium chloride: (force of attraction) between positive and negative ions/ionic bonding (1)
Question
Ethanol is manufactured by two different processes.
(a) For each process, name the organic reactant and state the type of reaction.
organic reactant ……………………………………….. type of reaction ……………………………………….
organic reactant ……………………………………….. type of reaction ………………………………………. [4]
(b) Alcohols can be oxidised to form carboxylic acids.
Name a suitable oxidising agent for this reaction.
……………………………………………………………………………………………………………………………. [1]
(c) Alcohols can be partially oxidised to form aldehydes.
Aldehydes are a homologous series of organic compounds.
Partial oxidation is achieved by reacting an alcohol with the oxidising agent in distillation apparatus as shown.
(i) Name apparatus A. ……………………………………………………………………………………………………………………… [1]
(ii) On the diagram, use one arrow to show where water enters apparatus A. [1]
(d) The table shows some information about aldehydes.
(i) Complete the table.
[2]
(ii) Deduce the general formula of aldehydes. [1]
(e) The structural formula of ethanal is shown.
The C=O group in aldehydes is at the end of the carbon chain.
This is a reactive part of the molecule.
(i) What is the name given to the reactive part of any organic molecule?
……………………………………………………………………………………………………………………… [1]
(ii) Complete the dot-and-cross diagram to show the electron arrangement of a molecule of ethanal. Inner shells have been drawn.
(f) Propanone belongs to a homologous series called ketones. Ketones have the same $\mathrm{C}=\mathrm{O}$ group as aldehydes but the $\mathrm{C}=\mathrm{O}$ group is not at the end of the carbon chain. Propanone has the same molecular formula as propanal, $\mathrm{C}_3 \mathrm{H}_6 \mathrm{O}$.
(i) What term is used to describe molecules with different structures but with the same molecular formula?[1]
(ii) Suggest the structure of propanone, $\mathrm{C}_3 \mathrm{H}_6 \mathrm{O}$. Show all of the atoms and all of the bonds.[2] [Total: 17]
▶️Answer/Explanation
Ans:
5(a) M1 sugar(s)
M2 fermentation
M3 ethene
M4 hydration
5(b) (acidified) potassium manganate(VII)
5(c)(i) (Liebig) condenser
5(c)(ii) arrow at the lower inlet
5(d)(i) methanal
$\mathrm{C}_4 \mathrm{H}_8 \mathrm{O}$
5(d)(ii) $\quad \mathrm{C}_n \mathrm{H}_{2 n} \mathrm{O}$
5(e)(i) functional group
5(e)(ii) M1 $4 \times \mathrm{C}-\mathrm{H}$ dot cross bonds and $1 \mathrm{C}-\mathrm{C}$ dot cross bond M2 $1 \times \mathrm{C}=\mathrm{O}$ dot cross bond M3 non-bonding electrons on $\mathrm{O}$
5(f)(i) (structural) isomers
5(f)(ii) M1 any structure with correct valencies and formula of $\mathrm{C}_3 \mathrm{H}_6 \mathrm{O}$ $\mathrm{M} 2 \mathrm{C}=\mathrm{O}$ bond on second carbon (of a chain of 3 )
Question
Sulfur dioxide, $\mathrm{SO}_2$, is used in the manufacture of sulfuric acid.
(a) In the first stage of the process, sulfur dioxide is obtained from sulfur-containing ores. Name one of these ores.[1]
(b) The next stage of the process is a reaction which can reach equilibrium. The equation for this stage is shown.
$
2 \mathrm{SO}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{SO}_3(\mathrm{~g})
$
(i) Describe two features of an equilibrium.[2]
(ii) Name the catalyst used in this stage.[1]
(iii) Why is a catalyst used?[1]
(iv) Explain, in terms of particles, why a high temperature increases the rate of this reaction.[3]
(v) In this stage, only a moderate temperature of $450^{\circ} \mathrm{C}$ is used.
What does this suggest about the forward reaction?[1]
(vi) Calculate the percentage by mass of sulfur in sulfur trioxide, $\mathrm{SO}_3$.
percentage $=$
(c) Concentrated sulfuric acid is a dehydrating agent which can chemically remove water from substances.
Both hydrated copper(II) sulfate crystals and sucrose (a sugar), $\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}$, can be completely dehydrated by concentrated sulfuric acid.
Name the solid product formed in each case.
hydrated copper(II) sulfate crystals……………………………..
sucrose……………………… [2]
(d) When propan-1-ol is heated with concentrated sulfuric acid as a catalyst an unsaturated hydrocarbon of relative molecular mass 42 is formed and one other product.
(i) What is meant by the term unsaturated?[1]
(ii) Write the chemical equation for this reaction.[2]
(iii) Name the unsaturated hydrocarbon formed.[1] [Total: 17]
▶️Answer/Explanation
Ans:
3(a) zinc blende
3(b)(i) reaction is reversible
rate of forward reaction = rate of reverse reaction
3(b)(ii) vanadium(V) oxide
3(b)(iii) increases the rate of reaction 1
3(b)(iv) particles have more energy (E) 1
rate of collisions increase 1
a higher proportion of particles have energy greater than activation energy $(E > E_{A})$
3(b)(v) exothermic
3(b)(vi)
$M_{\text {r }}$ of $\mathrm{SO}_3=80$
$100 \times \frac{32}{80}=40 \%$
3(c) anhydrous copper(II) sulfate carbon
3(d)(i) not all (C–C) bonds are single
3(d)(ii)
$\begin{aligned} & \mathrm{C}_3 \mathrm{H}_7 \mathrm{OH} \rightarrow \mathrm{C}_3 \mathrm{H}_6+\mathrm{H}_2 \mathrm{O} \\ & \mathrm{M}_1 \mathrm{C}_3 \mathrm{H}_6 \\ & \mathrm{M} 2 \text { rest of the equation }\end{aligned}$
3(d)(iii) propene