List, with an explanation, the three compounds in order of increasing carbon to oxygen bond length (shortest first).

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1 T4-2P1 [226 marks] 1. Which statement best describes the intramolecular bonding in HCN(l)? A. Electrostatic attractions between H + and CN ions B. Only van der Waals forces C. Van der Waals forces and hydrogen bonding D. Electrostatic attractions between pairs of electrons and positively charged nuclei 2. Which molecule has the shortest bond between carbon atoms? A. C 2 H 6 B. C. D. C 2 H 4 C 2 H 2 C 2 H 4 Cl 2 3a. Draw the Lewis structures for carbon monoxide, CO, carbon dioxide, CO 2 and methanol, CH 3 OH. 3b. List, with an explanation, the three compounds in order of increasing carbon to oxygen bond length (shortest first). Predict the shape and bond angles for the following species: 3c. CO 2 3d. CO 2 3 3e. BF 4 3f. Define a Brønsted-Lowry acid. 3g. Deduce the two acids and their conjugate bases in the following reaction: H 2 O(l) + NH 3 (aq) OH (aq) + NH + 4 (aq) Ethanoic acid, CH 3 COOH, is a weak acid. 3h. Define the term weak acid and state the equation for the reaction of ethanoic acid with water. 3i. Vinegar, which contains ethanoic acid, can be used to clean deposits of calcium carbonate from the elements of electric kettles. State the equation for the reaction of ethanoic acid with calcium carbonate.

2 Aspirin, one of the most widely used drugs in the world, can be prepared according to the equation given below. 4a. 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. 4b. Determine the amount, in mol, of salicylic acid, C 6 H 4 (OH)COOH, used. 4c. Calculate the theoretical yield, in g, of aspirin, C 6 H 4 (OCOCH 3 )COOH.

3 4d. Determine the percentage yield of pure aspirin. 4e. State the number of significant figures associated with the mass of pure aspirin obtained, and calculate the percentage uncertainty associated with this mass. 4f. 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.

4 The following is a three-dimensional computer-generated representation of aspirin. 4g. A third student measured selected bond lengths in aspirin, using this computer program and reported the following data. The following hypothesis was suggested by the student: Since all the measured carbon-carbon bond lengths are equal, all the carbonoxygen bond lengths must also be equal in aspirin. Therefore, the C8 O4 bond length must be m. Comment on whether or not this is a valid hypothesis. 4h. The other product of the reaction is ethanoic acid, CH 3 COOH. Define an acid according to the Brønsted-Lowry theory and state the conjugate base of CH 3 COOH. Brønsted-Lowry definition of an acid: Conjugate base of CH 3 COOH:

5 Nitrogen and silicon belong to different groups in the periodic table. 5a. Distinguish in terms of electronic structure, between the terms group and period. 5b. State the maximum number of orbitals in the n = 2 energy level. Draw the Lewis structures, state the shapes and predict the bond angles for the following species. 5c. SiF 2 6 5d. NO + 2 5e. Explain, using diagrams, why NO 2 is a polar molecule but CO 2 is a non-polar molecule. Consider the molecule HCONH 2. 5f. Explain the term hybridization. 5g. Describe how σ and π bonds form. 5h. State the type of hybridization of the carbon and nitrogen atoms in HCONH 2. 6a. Define the term isotopes. 6b. A sample of silicon contains three isotopes. Calculate the relative atomic mass of silicon using this data. 6c. Describe the structure and bonding in silicon dioxide and carbon dioxide. [4 marks] 6d. Draw the Lewis structure of NH3, state its shape and deduce and explain the H N H bond angle in NH 3. [4 marks]

6 6e. The graph below shows the boiling points of the hydrides of group 5. Discuss the variation in the boiling points. [4 marks] 6f. Explain, using diagrams, why CO and NO 2 are polar molecules but CO 2 is a non-polar molecule. [5 marks] Ethene, C2H 4, and hydrazine, N2H 4, are hydrides of adjacent elements in the periodic table. 7a. (i) Draw Lewis (electron dot) structures for C 2 H 4 and N 2 H 4 showing all valence electrons. (ii) State and explain the H C H bond angle in ethene and the H N H bond angle in hydrazine. [7 marks] The polarity of a molecule can be explained in terms of electronegativity. 7b. (i) Define the term electronegativity. [4 marks] (ii) Compare the relative polarities of the C H bond in ethene and the N H bond in hydrazine. (iii) Hydrazine is a polar molecule and ethene is non-polar. Explain why ethene is non-polar. 7c. The boiling point of hydrazine is much higher than that of ethene. Explain this difference in terms of the intermolecular forces in each compound. 7d. Hydrazine is a valuable rocket fuel. The equation for the reaction between hydrazine and oxygen is given below. N 2 H 4 (g) + O 2 (g) N 2 (g) + 2H 2 O(g) Use the bond enthalpy values from Table 10 of the Data Booklet to determine the enthalpy change for this reaction. 7e. State the name of the product and identify the type of reaction which occurs between ethene and hydrogen chloride. The reaction between N2H 4(aq) and HCl (aq) can be represented by the following equation. N 2 H 4 (aq) + 2HCl(aq) N 2 H 2+ 6 (aq) + 2Cl (aq) 7f. (i) Identify the type of reaction that occurs. (ii) Predict the value of the H N H bond angle in N 2 H Hydrazine, N2H 4, is a valuable rocket fuel. 8a. (i) Draw the Lewis (electron dot) structure for N2H4 showing all valence electrons. [4 marks] (ii) State and explain the H N H bond angle in hydrazine.

7 8b. Hydrazine and ethene, C2H 4, are hydrides of adjacent elements in the periodic table. The boiling point of hydrazine is much higher than that of ethene. Explain this difference in terms of the intermolecular forces in each compound. The equation for the reaction between hydrazine and oxygen is given below. N 2 H 4 (l) + O 2 (g) N 2 (g) + 2H 2 O(l) 8c. (i) The enthalpy change of formation, ΔH Θ, of liquid hydrazine is 50.6 kjmol 1. Use this value, together with data from Table [16 marks] f 12 of the Data Booklet, to calculate the enthalpy change for this reaction. (ii) (iii) Use the bond enthalpy values from Table 10 of the Data Booklet to determine the enthalpy change for this reaction. Identify the calculation that produces the most accurate value for the enthalpy change for the reaction given and explain your choice. (iv) Calculate ΔS Θ for the reaction using the data below and comment on its magnitude. (v) Calculate ΔG Θ for the reaction at 298 K. (vi) Predict, giving a reason, the spontaneity of the reaction above at both high and low temperatures. The reaction between N 2 H 4 (aq) and HCl(aq) can be represented by the following equation. N 2 H 4 (aq) + 2HCl(aq) N 2 H 2+ 6 (aq) + 2Cl (aq) 8d. The reaction between N 2 H 4 (aq) and HCl(aq) can be represented by the following equation. N 2 H 4 (aq) + 2HCl(aq) N 2 H 2+ 6 (aq) + 2Cl (aq) (i) Identify the type of reaction that occurs. (ii) Predict the value of the H N H bond angle in N 2 H (iii) Suggest the type of hybridization shown by the nitrogen atoms in N 2 H Which bonds are arranged in order of increasing polarity? A. H F < H Cl < H Br < H I B. H I < H Br < H F < H Cl C. H I < H Br < H Cl < H F D. H Br < H I < H Cl < H F 10. When C 2 H 2, C 2 H 4 and C 2 H 6 are arranged in order of increasing carbon-carbon bond strength (weakest bond first), what is the correct order? A. B. C. D. C 2 H 2, C 2 H 4, C 2 H 6 C 2 H 2, C 2 H 6, C 2 H 4 C 2 H 6, C 2 H 4, C 2 H 2 C 2 H 6, C 2 H 2, C 2 H The number of electrons in the valence shell of elements A and B, are 6 and 7 respectively. What is the formula and type of bonding in a compound formed by these elements? A. A 2 B, covalent B. AB 2, covalent C. A 2 B, ionic D. AB 2, ionic

8 Carbon and silicon belong to the same group of the periodic table. State the period numbers of both carbon and silicon. 12a. Describe and compare three features of the structure and bonding in the three allotropes of carbon: diamond, graphite and C 12b. 60 fullerene. [6 marks]

9 Both silicon and carbon form oxides. 12c. Draw the Lewis structure of CO 2 and predict its shape and bond angle. 12d. Describe the structure and bonding in SiO 2. 12e. Explain why silicon dioxide is a solid and carbon dioxide is a gas at room temperature.

10 Describe the bonding within the carbon monoxide molecule. 12f. 12g. Silicon has three stable isotopes, 28 Si, 29 Si and 30 Si. The heaviest isotope, 30 Si, has a percentage abundance of 3.1%. Calculate the percentage abundance of the lightest isotope to one decimal place. 13. Which bond is the least polar? A. C H B. F H C. O H D. N H 14. Which statement about the physical properties of substances is correct? A. The only solids that conduct electricity are metals. B. All substances with covalent bonds have low melting points. C. Ionic solids are always brittle. D. All metals have high densities. 15. Which single covalent bond is the most polar, given the following electronegativity values? A. C O B. S H C. C H D. O H

11 An organic compound, X, with a molar mass of approximately 88 g mol 1 contains 54.5% carbon, 36.3% oxygen and 9.2% hydrogen by mass. (i) Distinguish between the terms empirical formula and molecular formula. 16a. Empirical formula: [9 marks] Molecular formula: (ii) Determine the empirical formula of X. (iii) Determine the molecular formula of X. (iv) (v) (vi) X is a straight-chain carboxylic acid. Draw its structural formula. Draw the structural formula of an isomer of X which is an ester. The carboxylic acid contains two different carbon-oxygen bonds. Identify which bond is stronger and which bond is longer. Stronger bond: Longer bond:

12 (i) State and explain which of propan-1-ol, CH, and methoxyethane,, is more volatile. 16b. 3 CH 2 CH 2 OH CH 3 OCH 2 CH 3 [5 marks] (ii) Propan-1-ol, CH 3 CH 2 CH 2 OH, and hexan-l-ol, CH 3 (CH 2 ) 4 CH 2 OH, are both alcohols. State and explain which compound is more soluble in water.

13 16c. Graphite is used as a lubricant and is an electrical conductor. Diamond is hard and does not conduct electricity. Explain these statements in terms of the structure and bonding of these allotropes of carbon. [6 marks] Graphite: Diamond: An organic compound, X, with a molar mass of approximately 88 g mol 1 contains 54.5% carbon, 36.3% oxygen and 9.2% hydrogen by mass. Predict and explain the bond lengths and bond strengths of the carbon-oxygen bonds in CH. 17a. 3 CH 2 COO

14 (i) 17b. State the meaning of the term hybridization. [7 marks] (ii) Describe the hybridization of the carbon atom in methane and explain how the concept of hybridization can be used to explain the shape of the methane molecule. (iii) Identify the hybridization of the carbon atoms in diamond and graphite and explain why graphite is an electrical conductor.

15 Aluminium chloride, Al, does not conduct electricity when molten but aluminium oxide,, does. Explain this in terms of 17c. 2 Cl 6 Al 2 O 3 the structure and bonding of the two compounds. [4 marks] Al 2 Cl 6 : Al 2 O 3 : 18. Which statements are correct for the bonds between two carbon atoms? I. Single bonds are longer than triple bonds. II. III. Single bonds are stronger than double bonds. Triple bonds are stronger than double bonds. A. I and II only B. I and III only C. II and III only D. I, II and III Calcium nitrate contains both covalent and ionic bonds. State the formula of both ions present and the nature of the force between these ions. 19a. Ions: Nature of force:

16 19b. State which atoms are covalently bonded. Bonding in the nitrate ion involves electron delocalization. Explain the meaning of electron delocalization and how it affects the ion. 19c. Nitrogen also forms oxides, which are atmospheric pollutants. 19d. Outline the source of these oxides. State one product formed from their reaction with water. 19e. State one environmental problem caused by these atmospheric pollutants. 19f.

17 Calcium nitrate contains both covalent and ionic bonds. 20a. State the formula of both ions present and the nature of the force between these ions. Ions: Nature of force: 20b. State which atoms are covalently bonded. Nitrogen also forms oxides, which are atmospheric pollutants. 20c. Outline the source of these oxides. State one product formed from their reaction with water. 20d. State one environmental problem caused by these atmospheric pollutants. 20e.

18 In December 2010, researchers in Sweden announced the synthesis of N,N dinitronitramide, N(NO 2 ) 3. They speculated that this compound, more commonly called trinitramide, may have significant potential as an environmentally friendly rocket fuel oxidant. 21a. Methanol reacts with trinitramide to form nitrogen, carbon dioxide and water. Deduce the coefficients required to balance the equation for this reaction. N(NO 2 ) 3 (g)+ CH 3 OH(l) N 2 (g)+ CO 2 (g)+ H 2 O(l) Calculate the enthalpy change, in kj mol, when one mole of trinitramide decomposes to its elements, using bond enthalpy data 21b. 1 from Table 10 of the Data Booklet. Assume that all the N O bonds in this molecule have a bond enthalpy of 305 kj mol 1. 21c. Outline how the length of the N N bond in trinitramide compares with the N N bond in nitrogen gas, N 2.

19 21d. Deduce the N N N bond angle in trinitramide and explain your reasoning. Predict, with an explanation, the polarity of the trinitramide molecule. 21e.

20 Methanol can also be burnt as a fuel. Describe an experiment that would allow the molar enthalpy change of combustion to be 21f. calculated from the results. 21g. Explain how the results of this experiment could be used to calculate the molar enthalpy change of combustion of methanol.

21 Predict, with an explanation, how the result obtained would compare with the value in Table 12 of the Data Booklet. 21h. In December 2010, researchers in Sweden announced the synthesis of N,N dinitronitramide, N(NO 2 ) 3. They speculated that this compound, more commonly called trinitramide, may have significant potential as an environmentally friendly rocket fuel oxidant. 22a. Methanol reacts with trinitramide to form nitrogen, carbon dioxide and water. Deduce the coefficients required to balance the equation for this reaction. N(NO 2 ) 3 (g)+ CH 3 OH(l) N 2 (g)+ CO 2 (g)+ H 2 O(l) Calculate the enthalpy change, in kj mol, when one mole of trinitramide decomposes to its elements, using bond enthalpy data 22b. 1 from Table 10 of the Data Booklet. Assume that all the N O bonds in this molecule have a bond enthalpy of 305 kj mol 1. 22c. The entropy change, ΔS, for the decomposition of trinitramide has been estimated as +700 JK 1 mol 1. Comment on the sign of ΔS.

22 Using +700 JK as the value for the entropy change, along with your answer to part (c), calculate, in, for 22d. 1 mol 1 ΔG kj mol 1 this reaction at 300 K. (If you did not obtain an answer for part (c), then use the value 1000 kj mol 1, but this is not the correct value.) Explain how changing the temperature will affect whether or not the decomposition of trinitramide is spontaneous. 22e. 22f. Outline how the length of the N N bond in trinitramide compares with the N N bond in nitrogen gas, N 2.

23 Deduce the N N N bond angle in trinitramide and explain your reasoning. 22g. Predict, with an explanation, the polarity of the trinitramide molecule. 22h. International Baccalaureate Organization 2017 International Baccalaureate - Baccalauréat International - Bachillerato Internacional Printed for BLUPS