Silicon tetrachloride, SiCl4, is formed when silicon reacts with chlorine under suitable conditions. It is a colourless liquid with a low boiling point.

1. (a)Explain why SiCl4 has a low boiling point.[2]
2. (b)(i)Write an equation for this reaction.[1]
3. (b)(ii)Describe two visual observations when silicon tetrachloride is added drop by drop to a small amount of water. 1 2[2]
4. (b)(iii)A sample of 0.8505 g of SiCl4 is added to 800 cm³ of water. All of the soluble acidic product is dissolved in the water. Calculate the pH of the solution obtained.[3]
5. (c)(i)Silicon tetrachloride can be prepared according to reaction 1. reaction 1 Si(s) + 2Cl2(g) → SiCl4(l) ∆S® = −225.7 J K⁻¹ mol⁻¹ standard entropy of silicon, Sº Si(s) 18.7 J K⁻¹ mol⁻¹ standard entropy of silicon tetrachloride, S° SiCl4 (l) 239.0 J K⁻¹ mol⁻¹ Calculate the standard entropy of chlorine, S° Cl2(g). Show all your working.[2]
6. (c)(ii)Explain why the entropy change for reaction 1 is negative.[1]
7. (d)The standard enthalpy change of formation of silicon tetrachloride, ∆H SiCl4(l), is –640 kJ mol⁻¹. Reaction 1 is spontaneous at lower temperatures, but it is not spontaneous at very high temperatures. Calculate the temperature above which reaction 1 is not spontaneous.[2]