When calcium carbide reacts with water, ethyne and calcium hydroxide are produced. Write a balanced equation for this reaction.
Ethyne may also be prepared from ethene through the following reaction sequence: $\mathrm{CH_2CH_2} \xrightarrow{\text{step 1}} \mathrm{ClCH_2CH_2Cl} \xrightarrow{\text{step 2}} \mathrm{HC{\equiv}CH}$. What reaction types occur in step 1 and step 2?
Suggest which reagent and conditions would be used in a laboratory for step 2.
When ethyne is passed into water at $60^{\circ}\mathrm{C}$, in the presence of a little $\mathrm{H_2SO_4}$ and $\mathrm{Hg^{2+}}$ ions, a pungent, colourless organic liquid $Q$, with $M_r$ of 44 is obtained (step 3). When $Q$ is warmed with Tollens’ reagent in a test-tube, a silver mirror is formed. On acidification, the solution remaining in the test-tube is found to contain the organic compound $R$ which has $M_r$ of 60 (step 4). Give the structural formulae of $Q$ and $R$.
What type of reaction occurs in step 3 and step 4?
The standard enthalpy change of combustion of $\text{C}_2\text{H}_2$, $\Delta H_c^{\circ}$, is $-1300\,\text{kJ mol}^{-1}$ at $298\,\text{K}$. Values of relevant standard enthalpy changes of formation, $\Delta H_f^{\circ}$, measured at $298\,\text{K}$ are given: $\text{CO}_2(g)$, $-394\,\text{kJ mol}^{-1}$; $\text{H}_2\text{O}(l)$, $-286\,\text{kJ mol}^{-1}$. Write balanced equations, with state symbols, that represent the standard enthalpy change of combustion, $\Delta H_c^{\circ}$, of $\text{C}_2\text{H}_2$ and the standard enthalpy change of formation, $\Delta H_f^{\circ}$, of $\text{C}_2\text{H}_2$.
Using the data above and your answer to part (i), calculate the standard enthalpy change of formation, $\Delta H_f^{\circ}$, of $\text{C}_2\text{H}_2$. Show clearly whether the standard enthalpy change of formation of $\text{C}_2\text{H}_2$ is positive or negative.