3.4. Covalent bonding and coordinate (dative covalent) bonding
A subsection of Chemistry, 9701, through 3. Chemical bonding
Listing 10 of 93 questions
Iodine is an element in Group17 of the Periodic Table. At room temperature, iodine solid has a lattice structure. Describe the arrangement of the iodine molecules within the solid. List all of the forces of attraction present in solid iodine and identify which of these are overcome when solid iodine is heated to produce iodine vapour. forceof attraction present forceof attraction overcome  Iodine reacts with aluminium to form a white solid, Al 2I6. The diagram shows the arrangement of the outer electrons within a molecule of Al 2I6. Al Al I I I I I I How many co-ordinate (dative covalent) bonds are made when a molecule of Al 2I6 is formed from its atoms? Describe how co-ordinate (dative covalent) bonds form within this molecule. In a reaction between hydrogen iodide and concentrated sulfuric acid, the products are hydrogensulfide, sulfur, iodine and water. Write an equation for this reaction. You may wish to use oxidation numbers to help you. Explain, with reference to oxidation numbers, why this reaction is a redox reaction. 
9701_s19_qp_23
THEORY
2019
Paper 2, Variant 3
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Sketches of the shapes of some atomic orbitals are shown. Identify the type of orbital, s, p, or d. x y z x y z x y z shape of orbital type of orbital  Cadmium forms the two ions, Cd2 2+ and Cd2+. The electronic configuration of cadmium in these ions is shown. ● ● 4d105s1 ● ● 4d10 Use this information to explain why cadmium is not a transition element. Methylamine, CH3NH2, is a monodentate ligand. State what is meant by the term monodentate in this context. In the presence of aqueous methylamine, [Cd(H2O)6]2+ reacts to form a mixture of two isomeric octahedral complexes. equilibrium 1 [Cd(H2O)6]2+ + 4CH3NH2 [Cd(CH3NH2)4(H2O)2]2+ + 4H2O = –57 kJ mol–1 Complete the three-dimensional diagrams to show the isomers of [Cd(CH3NH2)4(H2O)2]2+. Use L to represent CH3NH2 in your diagrams. Cd Cd  State what is meant by the term stability constant. Complete the table by placing one tick () in each row to suggest how increasing temperature will affect Kstab and the equilibrium concentration of the cadmium complex, [[Cd(CH3NH2)4(H2O)2]2+], for equilibrium1. Explain your answer. decreases no change increases Kstab [[Cd(CH3NH2)4(H2O)2]2+] explanation  EDTA4– is a polydentate ligand. When a solution of EDTA4– is added to [Cd(H2O)6]2+ a new complex 2– is formed. The values for the stability constants for two Cd2+ complexes are shown. Kstab [Cd(CH3NH2)4(H2O)2]2+ 4.0 × 106 2– 4.0 × 1016 A solution containing equal numbers of moles of CH3NH2 and EDTA is added to [Cd(H2O)6]2+. Predict which complex is formed in the larger amount. Explain your answer. Methylamine is a Brønsted-Lowry base. Write an equation showing how methylamine dissolves in water to give an alkaline solution. Methylamine is a useful reagent in organic chemistry. Write an equation for the reaction of ethanoyl chloride with methylamine. Methylamine also reacts with propanone to form compound P as shown. H3C H3C C O H2N CH3 CH3 + H2O + H3C H3C C N P Deduce the type of reaction shown here. 
9701_s19_qp_41
THEORY
2019
Paper 4, Variant 1
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Sketch the shape of a d orbital.  Explain what is meant by the term transition element. Transition elements can form complex ions which contain ligands. Name the type of bonding that occurs between a ligand and a transition element. Give the formulae of two oxides of iron. State the oxidation number of iron in each compound. CO and CN– are monodentate ligands. Complete the table for the following two complexes. metal ion ligand co-ordination number formula of complex ion charge of complex ion Ni2+ CO Fe3+ CN– 3-  Transition element complexes can exhibit stereoisomerism. [Cu(H2O)4(NH3)2]2+ and Pt(NH3)2Cl 2 show the same type of isomerism. Name this type of isomerism. Complete the three-dimensional diagrams of the two isomers for [Cu(H2O)4(NH3)2]2+ and Pt(NH3)2Cl 2. Cu Cu Pt Pt  Copper can form complexes with the ligands ammonia and en, H2NCH2CH2NH2, as shown. [Cu(H2O)6]2++ en[Cu(H2O)4]2++ 2H2OKstab = 3.98 × 1010 equilibrium4 [Cu(H2O)6]2++ 2NH3[Cu(H2O)4(NH3)2]2++ 2H2OKstab = 5.01 × 107 equilibrium5 Write an expression for the stability constant, Kstab, for equilibrium5. State its units. Kstab =  units =  The standard entropy change, ΔS o, for equilibrium4 is +23 J K–1 mol–1 and for equilibrium5 is –8.4 J K–1 mol–1. Suggest an explanation for this difference by reference to both equilibria. Of the three copper complexes in equilibria 4 and 5, state the formula of the copper complex that is the most stable and explain your choice. copper complex explanation  
9701_s19_qp_42
THEORY
2019
Paper 4, Variant 2
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Sketches of the shapes of some atomic orbitals are shown. Identify the type of orbital, s, p, or d. x y z x y z x y z shape of orbital type of orbital  Cadmium forms the two ions, Cd2 2+ and Cd2+. The electronic configuration of cadmium in these ions is shown. ● ● 4d105s1 ● ● 4d10 Use this information to explain why cadmium is not a transition element. Methylamine, CH3NH2, is a monodentate ligand. State what is meant by the term monodentate in this context. In the presence of aqueous methylamine, [Cd(H2O)6]2+ reacts to form a mixture of two isomeric octahedral complexes. equilibrium 1 [Cd(H2O)6]2+ + 4CH3NH2 [Cd(CH3NH2)4(H2O)2]2+ + 4H2O = –57 kJ mol–1 Complete the three-dimensional diagrams to show the isomers of [Cd(CH3NH2)4(H2O)2]2+. Use L to represent CH3NH2 in your diagrams. Cd Cd  State what is meant by the term stability constant. Complete the table by placing one tick () in each row to suggest how increasing temperature will affect Kstab and the equilibrium concentration of the cadmium complex, [[Cd(CH3NH2)4(H2O)2]2+], for equilibrium1. Explain your answer. decreases no change increases Kstab [[Cd(CH3NH2)4(H2O)2]2+] explanation  EDTA4– is a polydentate ligand. When a solution of EDTA4– is added to [Cd(H2O)6]2+ a new complex 2– is formed. The values for the stability constants for two Cd2+ complexes are shown. Kstab [Cd(CH3NH2)4(H2O)2]2+ 4.0 × 106 2– 4.0 × 1016 A solution containing equal numbers of moles of CH3NH2 and EDTA is added to [Cd(H2O)6]2+. Predict which complex is formed in the larger amount. Explain your answer. Methylamine is a Brønsted-Lowry base. Write an equation showing how methylamine dissolves in water to give an alkaline solution. Methylamine is a useful reagent in organic chemistry. Write an equation for the reaction of ethanoyl chloride with methylamine. Methylamine also reacts with propanone to form compound P as shown. H3C H3C C O H2N CH3 CH3 + H2O + H3C H3C C N P Deduce the type of reaction shown here. 
9701_s19_qp_43
THEORY
2019
Paper 4, Variant 3
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Carbonmonoxide gas, CO, and nitrogen gas, N2, are both diatomic molecules. The diagram shows the arrangement of outer electrons in a molecule of CO. C O State one similarity and one difference in the way the atoms in a carbon monoxide molecule are bonded together compared to the atoms in a nitrogen molecule. The table states the electronegativity values of carbon, nitrogen and oxygen atoms. C N O electronegativity 2.5 3.0 3.5 Use the electronegativity values and relevant details from the Data Booklet to complete the table below. N2 CO number of electrons per molecule typeof intermolecular (van der Waals’) force  N2is less reactive than COeven though N2has a lower bond energy than CO. Suggest why COis more reactive than N2. Both carbonmonoxide and nitrogen are gases at room temperature and pressure. They both behave like ideal gases under certain conditions. State the two conditions necessary for these two gases to approach ideal gas behaviour. Explain why N2behaves more like an ideal gas than COdoes at 20.0 °C and 101 kPa. Calculate the amount, in mol, of pure nitrogen gas which occupies 100 cm3 at 101 kPa and 20.0 °C. Use relevant information from the Data Booklet. Show your working. Assume nitrogen behaves as an ideal gas.  mol  
9701_s21_qp_21
THEORY
2021
Paper 2, Variant 1
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Questions Discovered
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