Describe the observations, and write equations for the reactions that happen, when silicon(IV) chloride and phosphorus(V) chloride are each added separately to water. silicon(IV) chloride phosphorus(V) chloride
Iron(III) chloride, $\text{FeCl}_3$, is used to remove unwanted copper from printed circuit boards (PCBs) by this reaction: $\text{2FeCl}_3(aq) + \text{Cu}(s) \rightarrow \text{2FeCl}_2(aq) + \text{CuCl}_2(aq)$ A solution whose $\text{Fe}^{3+}(aq)$ concentration had initially been $1.50\,\text{mol dm}^{-3}$ was used repeatedly to dissolve copper from the PCBs, and was then analysed by titration as follows. A $2.50\,\text{cm}^3$ portion of the partly-used solution was acidified and titrated with $0.0200\,\text{mol dm}^{-3}$ $\text{KMnO}_4$. This converts any $\text{FeCl}_2$ present in the solution back to $\text{FeCl}_3$. It was found that $15.0\,\text{cm}^3$ of $\text{KMnO}_4(aq)$ was needed to reach the end point. (i) Construct an ionic equation for the reaction between $\text{Fe}^{2+}$ and $\text{MnO}_4^-$ in acid solution.
Give here the $\text{Fe}^{2+} : \text{MnO}_4^-$ ratio from your equation in (i).
Calculate the amount, in moles, of $\text{MnO}_4^-$ used in the titration.
Calculate the amount of $\text{Fe}^{2+}$, in moles, present in $2.50\,\text{cm}^3$ of the partially-used-up solution.
Calculate the concentration, [$\text{Fe}^{2+}$], in the partially-used-up solution.
Calculate the mass of copper that $100\,\text{cm}^3$ of the partially-used-up solution could still dissolve.
When $\text{SiCl}_4$ vapour is passed over Si at red heat, $\text{Si}_2\text{Cl}_6$ is produced. $\text{Si}_2\text{Cl}_6$ contains a Si-Si bond. Reacting $\text{Si}_2\text{Cl}_6$ with $\text{Cl}_2$ regenerates $\text{SiCl}_4$. $\text{Si}_2\text{Cl}_6(g) + \text{Cl}_2(g) \rightarrow 2\text{SiCl}_4(g)$ Use bond energy data from the Data Booklet to work out $\Delta H^\circ$ for this reaction.
Calcium can form three calcium silicides, $\text{Ca}_2\text{Si}$, $\text{CaSi}$ and $\text{CaSi}_2$. The first of these reacts with water as shown below. $\ldots\ldots\text{Ca}_2\text{Si} + \ldots\ldots\text{H}_2\text{O} \rightarrow \ldots\ldots\text{Ca(OH)}_2 + \ldots\ldots\text{SiO}_2 + \ldots\ldots\text{H}_2$ (i) Balance the equation. You may find oxidation numbers useful. (ii) In this reaction, state which element(s) are oxidised, and which element(s) are reduced.