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Question 1
This question is about the element hydrogen and its compounds. Lithium amide (LiNH2) contains the amide ion, NH2-. |
a) | Draw the shape of the amide ion, NH2- Include any lone pairs and give the value of the bond angle.
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b) | Describe the requirements for hydrogen bonding between two molecules, A and B.
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c) | The table below shows the boiling points of ammonia, NH3, and hydrogen, H2. |
Explain the difference in boiling points.
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Question 2
a) | State the meaning of the term electronegativity.
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b) | The table below shows the Pauling electronegativity values of some Period 3 elements. |
Deduce the type of bonding in sulfur hexachloride, SCl6. Explain your reasoning, using the table of electronegativity values above.
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c) | Draw the shape of a molecule of SF6. Include a value of the F-S-F bond angle. Explain why SF6 has the shape you have drawn.
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Question 3
This question is about intermolecular forces. The table below shows some electronegativity values of some elements. |
a) | Using the data in the table above, predict the formula of the compound with the most polar bonds formed from two of these elements.
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b) | The Si-Cl bond is polar. Explain why SiCl4 is not a polar molecule.
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c) | State the strongest type of intermolecular force that exists between molecules of SiCl4.
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d) | Explain how induced dipole-dipole forces in a sample of SiCl4.
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e) | Suggest, in terms of intermolecular forces, why SiCl4 has a higher boiling point than SiHCl3.
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Question 4
This question is about the Group 3 element boron. Boron trifluoride can react with a fluoride ion as shown by the equation; BF3 + F- ➔ BF4- |
a) | Draw a diagram to show the shape of the BF3 molecule. State its shape.
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b) | Explain why the BF3 molecule has the shape that you have drawn in part a).
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c) | Draw a diagram to show the shape of the BF4- ion. State its shape.
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d) | Name the type of bond formed in the reaction between BF3 and F- to form BF4-. Explain how this bond is formed in terms of electrons involved.
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Question 5
The diagram below represents a molecule of hydrogen peroxide. |
a) | Predict a value for the H-O-O bond angle.
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b) | Hydrogen peroxide dissolves in water. State the strongest type of interaction that occurs between molecules of hydrogen peroxide and water.
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c) | Draw a diagram to show how one molecule of hydrogen peroxide interacts with one molecule of water. Include all lone pairs and partial charges in your diagram.
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d) | Explain, in terms of electronegativity, why the boiling point of H2O2 is higher than H2S2.
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Question 6
a) | Draw a diagram to show the shape of a molecule of ammonia. Include any lone pairs of electrons and give the value of the bond angle.
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b) | What is the name of the shape of the ammonia molecule, NH3?
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c) | Ammonia, NH3, can react with a hydrogen ion, H+, to form an ammonium ion, NH4+, which contains a dative covalent bond. Explain how the dative covalent bond in NH4+ is formed.
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d) | State the new shape and bond angle of the ammonium ion.
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Question 7
Ammonia reacts with aluminium chloride as shown by the equation: NH3 + AlCl3 ➔ H3NAlCl3 |
a) | Draw a diagram to illustrate the shape of a molecule of AlCl3. Give the value of the bond angle.
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b) | Name the type of bond formed between N and Al in H3NAlCl3.
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c) | Explain how the value of the Cl-Al-Cl bond angle in AlCl3 changes, if at all, on formation of the compound H3NAlCl3.
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Question 8
The table below shows some average bond enthalpies. |
a) | Compare the relative bond strength of the C-C single and C=C double bonds. Explain your answer.
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b) | Trichloroethene, C2HCl3, is a polar molecule. Annotate the diagram below to show the direction of the dipole in a molecule of trichloroethene. Include partial charges.
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c) | The boiling points of trichloroethene, C2HCl3, and tetrachloroethene, C2Cl4, are shown in the table below. |
Suggest, in terms of intermolecular forces, why C2Cl4 has a higher boiling point than C2HCl3.
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Question 9
This question is about H2O. |
a) | State the strongest type of interaction between molecules of water.
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b) | Draw a diagram to show hydrogen bonding between two molecules of H2O. Include all lone pairs and partial charges in your diagram. Label the hydrogen bond.
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c) | Hydrogen bonding in ice causes ice to have a lower density than water and ice to have a relativity high melting point. Explain why hydrogen bonding causes ice to have these anomalous properties.
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