Grade 11 Holiday Homework Chemistry HL

Transcription

1 Grade 11 Holiday Homework Chemistry HL 1. The percentage of iron(ii) ions, Fe 2+, in a vitamin tablet can be estimated by dissolving the tablet in dilute sulfuric acid and titrating with standard potassium manganate(vii) solution, KMnO 4 (aq). During the process iron(ii) is oxidized to iron(iii) and the manganate(vii) ion is reduced to the manganese(ii) ion, Mn 2+ (aq). It was found that one tablet with a mass of 1.43 g required 11.6 cm 3 of mol dm 3 KMnO 4 (aq) to reach the end-point. (a) (i) State the half-equation for the oxidation of the iron(ii) ions. State the half-equation for the reduction of the MnO 4 ions in acidic solution. (iii) Deduce the overall redox equation for the reaction. (b) (i) Calculate the amount, in moles, of MnO 4 ions present in 11.6 cm 3 of mol dm 3 KMnO 4 (aq). Calculate the amount, in moles, of Fe 2+ ions present in the vitamin tablet.

2 (iii) Determine the percentage by mass of Fe 2+ ions present in the vitamin tablet. (Total 7 marks) 2. The electron configuration of chromium can be expressed as [Ar]4s x 3d y. (i) Explain what the square brackets around argon, [Ar], represent. State the values of x and y. x:... y:...

3 (iii) Annotate the diagram below showing the 4s and 3d orbitals for a chromium atom using an arrow, and, to represent a spinning electron. 4s 3d (Total 3 marks) 3(a) (i) Draw the shape of the p z orbital using the coordinates shown. State the electron configuration of Fe 3+. (iii) Define the term ligand.

4 (iv) Explain why the complex [Fe(H 2 O) 6 ] 3+ is coloured. (v) The element selenium (Z = 34) has electrons in the 4s, 3d and 4p orbitals. Draw an orbital box diagram (arrow-in-box notation) to represent these electrons. (Total 7 marks)

5 4. The graph below illustrates how the vapour pressures of ethoxyethane, CH 3 CH 2 OCH 2 CH 3, benzene, C 6 H 6, and water, H 2 O, change with temperature.

6 (a) Using data from the graph, explain the difference in vapour pressure of ethoxyethane, benzene and water at 30 C. (4) (b) Use the graph to determine the boiling point of benzene at standard pressure. (Total 5 marks)

7 5. Explain the meaning of the term hybridization. State the type of hybridization shown by the carbon atoms in carbon dioxide, diamond, graphite and the carbonate ion (Total 5 marks)

8 6. 1-chlorobutane can be converted to a pentylamine via a two stage process. Deduce equations for each step of this conversion including any catalyst required and name the organic product produced at each stage (Total 5 marks)

9 7. Propene can be hydrogenated in the presence of a nickel catalyst to form propane. Use the data below to answer the questions that follow. Compound Formula H O f / kj mol 1 S O / J K 1 mol 1 hydrogen H 2 (g) propane C 3 H 8 (g) propene C 3 H 6 (g) (i) Calculate the standard enthalpy change for the hydrogenation of propene. Calculate the standard entropy change for the hydrogenation of propene. (iii) Determine the value of G O for the hydrogenation of propene at 298 K.

10 (iv) At 298 K the hydrogenation of propene is a spontaneous process. Determine the temperature above which propane will spontaneously decompose into propene and hydrogen. (Total 8 marks) 8. (a) Draw the Lewis structures, state the shape and predict the bond angles for the following species. (i) PCl 3 NH 2 (iii) XeF 4 (Total 9 marks) (b) Describe the structure and bonding in silicon dioxide. (Total 2 marks)

11 (c). Magnesium is the eighth most abundant element in the earth s crust. The successive ionization energies of the element are shown below. (i) Define the term first ionization energy and state the equation for the first ionization of magnesium. Explain the general increase in successive ionization energies of the element. (iii) Explain the large increase between the tenth and eleventh ionization energies. (Total 8 marks) (d) (i) Define the term relative atomic mass (A r ). Relative atomic masses are obtained using a mass spectrometer. Draw a simple annotated diagram of the mass spectrometer. (5) (Total 6 marks)

12 9. (a) The lattice enthalpy of magnesium chloride can be calculated from the Born-Haber cycle shown below. (i) Identify the enthalpy changes labelled by I and V in the cycle. Use the ionization energies given in the cycle above and further data from the Data Booklet to calculate a value for the lattice enthalpy of magnesium chloride. (4) (iii) The theoretically calculated value for the lattice enthalpy of magnesium chloride is kj. Explain the difference between the theoretically calculated value and the experimental value.

13 (iv) The experimental lattice enthalpy of magnesium oxide is given in Table 13 of the Data Booklet. Explain why magnesium oxide has a higher lattice enthalpy than magnesium chloride. (Total 10 marks) (b). Aspirin, one of the most widely used drugs in the world, can be prepared according to the equation given below. (i) State the names of the three organic functional groups in aspirin. A student reacted some salicylic acid with excess ethanoic anhydride. Impure solid aspirin was obtained by filtering the reaction mixture. Pure aspirin was obtained by recrystallization. The following table shows the data recorded by the student. Mass of salicylic acid used Mass of pure aspirin obtained 3.15 ± 0.02 g 2.50 ± 0.02 g (iii) Determine the amount, in mol, of salicylic acid, C 6 H 4 (OH)COOH, used. Calculate the theoretical yield, in g, of aspirin, C 6 H 4 (OCOCH 3 )COOH.

14 Determine the percentage yield of pure aspirin. State the number of significant figures associated with the mass of pure aspirin obtained, and calculate the percentage uncertainty associated with this mass. Another student repeated the experiment and obtained an experimental yield of 150 %. The teacher checked the calculations and found no errors. Comment on the result. (Total 11 marks) (c). A toxic gas, A, consists of 53.8 % nitrogen and 46.2 % carbon by mass. At 273 K and Pa, g of A occupies 462 cm 3. Determine the empirical formula of A. Calculate the molar mass of the compound and determine its molecular structure. (Total 4 marks) 10. (a) Deduce an equation for the reaction between propanoic acid and methanol. Identify the catalyst and state the name of the organic compound, X, formed. Write an isomer of compound X and identify the class of compounds to which it belongs. (Total 6 marks) (b) 2-chloro-3-methylbutane reacts with sodium hydroxide via an S N 2 mechanism. Explain the mechanism by using curly arrows to represent the movement of electron pairs. (Total 4 marks)

15 (c) Existence of isomers leads to diversity of organic compounds. (i) Describe what is meant by the term stereoisomers. 1,3-dichlorocyclobutane exists as geometrical isomers, a form of stereoisomers. Draw and name the two geometrical isomers of 1,3-dichlorocyclobutane. Identify the isomer with the higher boiling point and explain your reasoning. (Total 7 marks) d) (i) Describe the elimination of HBr from bromoethane. Your answer should include the reagents, conditions and equation for the reaction. Explain the mechanism for the elimination of HBr from bromoethane. (5) (Total 8 marks)