(ii) State the reagent for the conversation indicated as step A.
(iii) What type of reaction will ethanol undergo CH\(_3\)CH\(_2\)COOH during the process of conversation indicated as step B?
(c)(i) Write three balanced equation for the complete combustion of ethanol in :date the volume of oxygen required at s.t.p for the complete combustion of ethanol. (H = 1, C = 12, O = 16, molar volume of gases at s.t.p. = 22.4 dm\(^3\))
(iii) State the importance of the non-volatile residue of the process named in (d)(iii) to the iron and steel industry.
(a)(i) Addition polymerization. It is the process in which many small unsaturated molecules (monomers containing C=C double bonds) join together to form a single large molecule (the polymer) without the loss of any small molecule.
(a)(ii) Type of compounds that undergo it: unsaturated organic compounds, that is alkenes (and other molecules containing a carbon-to-carbon double bond).
(a)(iii) Two factors affecting the strength of polymers:
- the chain length (relative molecular mass) of the polymer;
- the degree of branching / cross-linking between the chains (and the strength of intermolecular forces between chains).
(b) Reaction pathways of ethanol. Reading the diagram: ethanol (C2H5OH) reacts with propanoic acid (CH3CH2COOH) and an H+ catalyst to give X at the top; step A converts ethanol to CH3COOH; step B converts ethanol to C2H4.
(b)(i) Product X. Ethanol and propanoic acid undergo esterification, so X is ethyl propanoate.
\[ \text{CH}_3\text{CH}_2\text{COOH} + \text{C}_2\text{H}_5\text{OH} \xrightarrow{\text{H}^+} \text{CH}_3\text{CH}_2\text{COOC}_2\text{H}_5 + \text{H}_2\text{O} \]
Structural formula of X: CH3–CH2–C(=O)–O–CH2–CH3
(b)(ii) Reagent for step A (ethanol \(\rightarrow\) ethanoic acid): acidified potassium dichromate(VI), K2Cr2O7/H+ (acidified KMnO4 is also acceptable), used as an oxidising agent with heat under reflux.
(b)(iii) Type of reaction in step B (ethanol \(\rightarrow\) ethene): a dehydration (elimination) reaction, in which a molecule of water is removed.
\[ \text{C}_2\text{H}_5\text{OH} \xrightarrow[180^{\circ}\text{C}]{\text{conc. H}_2\text{SO}_4} \text{C}_2\text{H}_4 + \text{H}_2\text{O} \]
(c) Complete combustion of ethanol.
\[ \text{C}_2\text{H}_5\text{OH} + 3\text{O}_2 \rightarrow 2\text{CO}_2 + 3\text{H}_2\text{O} \]
From the equation, 1 mole of ethanol requires 3 moles of oxygen. At s.t.p. the volume of oxygen needed to burn one mole of ethanol completely is:
\[ V(\text{O}_2) = 3 \times 22.4 = 67.2\ \text{dm}^3 \]
(For a given mass \(m\) of ethanol, molar mass \(=46\), the volume is \(\dfrac{m}{46}\times 3\times 22.4\ \text{dm}^3\).)
(d)(i) Two substances produced when coal is heated in the absence of air: coke (solid residue) and coal gas; coal tar and ammoniacal liquor are also produced.
(d)(ii) Name of the process: destructive distillation of coal.
(d)(iii) Importance of the non-volatile residue (coke) to the iron and steel industry: coke is used in the blast furnace both as the fuel that supplies heat and as the reducing agent that reduces iron(III) oxide to iron:
\[ \text{Fe}_2\text{O}_3 + 3\text{CO} \rightarrow 2\text{Fe} + 3\text{CO}_2 \]
(the carbon monoxide reducer is itself generated from the burning coke).
