Chapter 1

The \(C-C\) bond length in a crystal of diamond is 0.154 nm. What is this distance in (a) metres, (b) picometres, (c) angstroms? (Section \(1.2)\)

Oxygen gas liquefies at \(-183.0^{\circ} \mathrm{C}\) and freezes at \(-218.4^{\circ} \mathrm{C}\) Work out its melting point, \(T_{\mathrm{m}},\) and boiling point, \(T_{\mathrm{b}},\) in kelvin. (Section \(1.2)\)

A sealed flask holds \(10 \mathrm{dm}^{3}\) of gas. What is this volume in (a) \(\left.\mathrm{cm}^{3},(\mathrm{b}) \mathrm{m}^{3}, \text { (c) litres? (Section } 1.2\right)\)

What is the Sl derived unit for the speed of a molecule? (Section \(1.2)\)

How many moles of atoms are contained in the following masses: (a) \(22.0 \mathrm{g}\) of magnesium; (b) \(43.2 \mathrm{g}\) of chlorine (c) \(126 \mathrm{mg}\) of gold; (d) \(1.00 \mathrm{kg}\) of mercury? (Section 1.3 )

A stream running out from a copper mine contains a dilute solution of copper sulfate. As it passes over an iron grid, copper metal deposits on the grid. (Section \(1.4)\) (a) Write a balanced equation, with state symbols, for the reaction taking place. (b) Write an ionic equation for the reaction. (c) Assign oxidation states to the elements in each of the reactants and products in the equation in (b). Use these values to decide what has been oxidized and what reduced.

(a) What are the systematic names for \((0) \mathrm{CS}_{2} ;(\mathrm{il}) \mathrm{Cl}_{2} \mathrm{O}_{7}\) (iii) \(\mathrm{XeF}_{6} ;(\mathrm{iv})\left(\mathrm{NH}_{4}\right)_{2} \mathrm{SO}_{4} ;(\mathrm{v}) \mathrm{CrCl}_{3} ;(\mathrm{vi}) \mathrm{KlO}_{4} ?\) (b) Write the formula of each of the following compounds: (i) sodium sulfite; (ii) barium carbonate; (iii) iron(II) chloride; (iv) sodium thiosulfate; (v) diiodine pentoxide; (vil) dinitrogen oxide. (Section 1.4 )

In most compounds, H has an oxidation state of +1 and 0 has an oxidation state of \(-2 .\) The following compounds are exceptions to this rule. Assume each metal has the oxidation state of its most common ion and that \(F\) has an oxidation state of \(-1 .\) Find the oxidation state of \(\mathrm{H}\) or \(\mathrm{O}\) in each compound: (a) \(\mathrm{KO}_{2}\) (b) \(\mathrm{Na}_{2} \mathrm{O}_{2} ;(\mathrm{c}) \mathrm{MgH}_{2}\) (d) \(\mathrm{LiAIH}_{4}\) (e) \(\left.\mathrm{OF}_{2} \text { . (Section } 1.4\right)\)

Sodium chromate \(\left(\mathrm{Na}_{2} \mathrm{CrO}_{4}\right)\) can be prepared by oxidizing a chromium(lil) salt with sodium peroxide (Na_O_) in alkaline solution. The \(\mathrm{Cr}^{3+}\) ions are oxidized to \(\mathrm{CrO}_{4}^{2-}\) ions. The \(\mathrm{O}_{2}^{2-}\) ions are reduced to OH' ions. Construct half equations and a balanced overall equation for the reaction. (Section \(1.4)\)

To prepare a very dilute solution, it is more accurate to make up a more concentrated standard solution, and carry out a series of successive dilutions, than to weigh out a very small mass of the solute. A solution was made by dissolving \(0.587 \mathrm{g}\) of \(\mathrm{KMnO}_{4}\) in dilute sulfuric acid and making the volume of solution up to \(1 \mathrm{dm}^{3}\) in a volumetric flask. \(10.0 \mathrm{cm}^{3}\) of this solution were transferred to a second \(1 \mathrm{dm}^{3}\) volumetric flask and diluted to the mark with water. The dilution process was then repeated once, that is, \(10.0 \mathrm{cm}^{3}\) of this solution were transferred to a \(1 \mathrm{dm}^{3}\) volumetric flask and diluted to the mark with water. (Section 1.5 ). (a) What mass (in \(\mathrm{mg}\) ) of \(\mathrm{KMnO}_{4}\) would you have had to weigh out to make \(500 \mathrm{cm}^{3}\) of a solution with the same concentration as the final dilute solution? (b) What is the concentration of the final dilute \(\mathrm{KMnO}_{4}\) solution in moldm \(^{-3} ?\)

The standard enthalpy change of combustion of heptane, \(\left.\mathrm{C}_{7} \mathrm{H}_{16}, \text { at } 298 \mathrm{K}, \text { is }-4817 \mathrm{kJmol}^{-1} \text {. (Section } 1.6\right)\) (a) Write a thermochemical equation for the complete combustion of heptane to carbon dioxide and water. (b) What is the enthalpy change when \(50 \mathrm{g}\) of heptane are bumed? (c) What mass of heptane would be needed to provide \(100 \mathrm{MJ}\) of energy?

(a) List the non-covalent interactions present in liquid water. Which is responsible for the strongest interactions between the molecules? (b) Explain why the value of \(\Delta_{\mathrm{vap}} H^{\mathrm{O}}\left(\mathrm{H}_{2} \mathrm{O}\right)\) is unusually high for a molecule of its size. (c) \(\ln\) a storm, \(3 \mathrm{cm}\) of rain falls on the city of Leeds, which has an area of approximately \(500 \mathrm{km}^{2}\). Estimate the energy released as heat when this quantity of water condenses from vapour to form rain. (Density of water is \(1.00 \mathrm{gcm}^{-3}\) \(\Delta_{\mathrm{vap}} H^{\mathrm{e}}\left(\mathrm{H}_{2} \mathrm{O}\right)=+40.7 \mathrm{kJmol}^{-1}\) at \(298 \mathrm{K}\) (d) The output from a large 2000 MW power station is \(2000 \mathrm{MJs}^{-1}\). How long would it take the power station to deliver the same quantity of energy as was released by the condensation of the rain in (c)? (Sections 1.7 and 1.8 )

Nitrogen dioxide gas is heated in a sealed container at \(700 \mathrm{K}\) until the system comes to equilibrium. The nitrogen dioxide dissociates into nitrogen monoxide and oxygen in an endothermic process (Section \(1.9)\) $$2 \mathrm{NO}_{2}(\mathrm{g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g})+\mathrm{O}_{2}(\mathrm{g})$$ The equilibrium constant at \(700 \mathrm{K}\) is \(2.78 \times 10^{-2} \mathrm{moldm}^{-3}\) (a) Write an expression for \(K_{c}\) (b) State how the position of equilibrium would be affected by: (1) an increase in temperature (ii) an increase in the total pressure. (c) At equilibrium at \(700 \mathrm{K}\), the concentration of nitrogen monoxide was found to be \(0.017 \mathrm{moldm}^{-3}\). What was the concentration of nitrogen dioxide in the equilibrium mixture?

One stage in the manufacture of methanol from methane involves the conversion of synthesis gas (a mixture of \(\mathrm{CO}\) and \(\mathrm{H}_{2}\) to methanol. The conversion is carried out over a catalyst at a temperature of around \(500 \mathrm{K}\) and a pressure of 100 atm. (Section \(1.9)\) $$\mathrm{CO}(\mathrm{g})+2 \mathrm{H}_{2}(\mathrm{g}) \rightleftharpoons \mathrm{CH}_{3} \mathrm{OH}(\mathrm{g}) \Delta H=-90.7 \mathrm{kJmol}^{-1}$$ (a) Write an expression for \(K_{p}\) for the reaction. (b) At \(500 \mathrm{K}\) and 100 atm pressure, an equilibrium mixture contains \(42 \% \mathrm{CH}_{3} \mathrm{OH}\) and \(48 \% \mathrm{CO}\). Calculate a value for \(K_{p}\) at this temperature. (c) Use Le Chatelier's principle to predict what would happen to the percentage of methanol in the mixture if: (i) the temperature increases; (ii) the pressure increases; (iii) hydrogen is added at constant temperature and pressure.