Identify substances K, M, and N, and explain their formation based on the reactions described.

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b) (i) Name substance

• (I) K: K reacts with water to produce calcium hydroxide ($\text{Ca(OH)}_2$) and Gas L. Gas L is identified as $\text{C}_2\text{H}_2$ (ethyne) because it reacts with 1 mole of $\text{H}_2$ to form $\text{C}_2\text{H}_4$ (ethene). The reaction of calcium carbide with water produces calcium hydroxide and ethyne.

  $$\text{CaC}_2(s) + 2\text{H}_2\text{O}(l) \rightarrow \text{Ca(OH)}_2(aq) + \text{C}_2\text{H}_2(g)$$

  Therefore, K is calcium carbide.

  $$\boxed{\text{Calcium carbide}}$$

• (II) M: Gas L ($\text{C}_2\text{H}_2$, ethyne) reacts with 2 moles of $\text{Cl}_2$ to form M. This is an addition reaction where the triple bond breaks, and chlorine atoms add to the carbons.

  $$\text{C}_2\text{H}_2(g) + 2\text{Cl}_2(g) \rightarrow \text{C}_2\text{H}_2\text{Cl}_4(l)$$

  The product M is 1,1,2,2-tetrachloroethane.

  $$\boxed{\text{1,1,2,2-tetrachloroethane}}$$

• (III) N: $\text{C}_2\text{H}_4$ (ethene) undergoes Step V with $\text{KMnO}_4/\text{H}^+$. This is the oxidation of an alkene by acidified potassium permanganate, which forms a diol.

  $$\text{CH}_2=\text{CH}_2 + [\text{O}] + \text{H}_2\text{O} \xrightarrow{\text{KMnO}_4/\text{H}^+} \text{CH}_2\text{OH}-\text{CH}_2\text{OH}$$

  The product N is ethane-1,2-diol.

  $$\boxed{\text{Ethane-1,2-diol}}$$

b) (ii) Name the catalyst used in step (IV)

Step IV shows the reaction of $\text{C}_2\text{H}_4$ (ethene) with $\text{H}_2\text{O}$ to form $\text{CH}_3\text{CH}_2\text{OH}$ (ethanol). This is the hydration of ethene. The catalyst used for this reaction is typically concentrated phosphoric(V) acid or sulfuric acid.

$$\boxed{\text{Phosphoric(V) acid}}$$

b) (iii) Draw the structural formula of

• (I) M: M is 1,1,2,2-tetrachloroethane ($\text{C}_2\text{H}_2\text{Cl}_4$).

  $$\begin{align*} &\quad \text{Cl} \quad \text{Cl} \\ &\quad | \quad | \\ \text{Cl}&-\text{C}-\text{C}-\text{Cl} \\ &\quad | \quad | \\ &\quad \text{H} \quad \text{H} \end{align*}$$

• (II) N: N is ethane-1,2-diol ($\text{CH}_2\text{OH}-\text{CH}_2\text{OH}$).

  $$\begin{align*} &\quad \text{H} \quad \text{H} \\ &\quad | \quad | \\ \text{H}&-\text{C}-\text{C}-\text{H} \\ &\quad | \quad | \\ &\quad \text{OH} \quad \text{OH} \end{align*}$$

c) Complete combustion of one mole of a hydrocarbon produced four moles of carbon (IV) oxide and four moles of water.