Bonding - Exam Questions

Mia Weaver
Flashcards by Mia Weaver, updated more than 1 year ago
Mia Weaver
Created by Mia Weaver over 1 year ago


Exam questions and answers on bonding

Resource summary

Question Answer
Explain how the ions are held together in solid sodium metal. (1 mark) - Attraction/electrostatic forces between positive metal ions/lattice and delocalised/free electrons
Explain how ions are held together in solid sodium chloride. (1 mark) - Electrostatic forces/attractions between oppositely charged ions.
The melting point of sodium chloride is much higher than that of sodium metal. What can be deduced from this information? (1 mark) - The ionic bonding in NaCl is stronger/requires more energy to break than the metallic bonding in Na
Compare the electrical conductivity of solid sodium metal with that of solid sodium chloride. Explain your answer. (3 marks) - Sodium conducts and sodium chloride does not conduct - Delocalised electrons flow through the metal - Ions can't move in solid salt
Explain why sodium metal is malleable. (1 mark) - Layers can slide over each other
In terms of electrons involved, explain how the bond between the BF3 molecule and the F- ion is formed. Name the type of bond formed in this reaction. (2 marks) - Lone pair donated / both electrons supplied by one atom from F- to B - Davite/coordinate bonding
Explain why the bond angle in an amide ion (NH2-) is smaller than that in an ammonia molecule (NH3). (2 marks) - More lone pairs on NH2- than on NH3 - Lone pairs repel more than bonding pairs so the bond angle is smaller
Describe the bonding that is present in metals. ( 3 marks) - Electrostatic forces of attraction between _ positive ions/cations - and delocalised electrons
Explain how the bonding and structure lead to the typical metallic properties of electrical conductivity and malleability. (4 marks) - Conductivity: Electrons are mobile/can move - electrons can act as charge carriers - Malleability: Cations/positive ions in the lattice are all identical/same size/ions can slide over one another - attractive forces remain the same throughout the lattice
Suggest a reason why aluminium is a better conductor of electricity than magnesium. (2 marks) - More electrons delocalised/more outer electrons - In aluminium compared with magnesium
Define the term electronegativity. (2 marks) - The ability of an atom to attract electrons - in a covalent bond
Name the strongest type of intermolecular force present in: - Liquid F2 - Liquid CH3F - Liquid HF (3 marks) - F2 = Van der Waals' - CH3F = Dipole-dipole - HF = Hydrogen bonding
Explain how the strongest type of intermolecular force in liquid HF arises. (3 marks) - A large difference in electronegativity between H and F - H-F dipole created (H slightly more positive and F slightly more negative) - Bond formed between H and lone pair on F
The boiling points of some hydrogen halides are HCl - 188, HBr - 206 and HI - 238. Explain the trend in boiling points of the hydrogen halides from Hcl to HI. (2 marks) - Van der Waals' forces - Increase with the increasing size/mass in the hydrogen halides
Explain why the O-H bond in a methanol molecule is polar. (2 marks) - Oxygen is more electronegative than hydrogen - Causing a higher e- density around the oxygen atom (causes delta charges on the O and H)
The boiling point of methanol is 65, the boiling point of oxygen is -183. Methanol and oxygen both have an Mr of 32. Explain in terms of the intermolecular forces, why the boiling point of methanol is much higher than that of oxygen. (3 marks) - Van der Waals' forces between oxygen molecules. _ Hydrogen bonding between methanol molecules - Hydrogen bonding is stronger than Van der Waals'
Why do diamond and graphite both have high melting points? (3 marks) - macromolecular - covalent - strong covalent bonds
Explain why magnesium has a higher melting point than sodium. (2 marks) - More protons (Mg2+ more than Na+) - attracts delocalised electrons more strongly. OR - Mg2+ has more delocalised electrons - so attracts positive ions more
Why is graphite a good conductor of electricity? (1 mark) - Delocalised electrons
Why is graphite soft? (2 marks) - Planes - with weak forces between them
By reference to all the atoms involved, explain in terms of electrons how Na2S is formed from its atoms. (2 marks) - Electrons are transferred from Na to S -2 electrons from the 2Na atoms
What change occurs to the motion of the ions in sodium chloride when it is heated from room temperature to a temperature below its melting point? (1 mark) - Vibrate faster
A chloride ion has one more electron than a chlorine atom. In the formation of sodium chloride, from where does this electron come? (1 mark) - from sodium
What property of the atoms joined by a covalent bond causes the bond to be polar? (1 mark) - Difference in electronegativity
Give the name of the type of bond formed when phosphine (PH3) reacts with an H+ ion. Explain how this bond is formed. (3 marks) - Dative/coordinate bond - lone pair - donated from P to H+
State and explain the trend in electronegativity values across Period 3 from sodium to chlorine. (3 marks) - Increases - nuclear charge increases - attracting electrons in the same shell. OR - similar shielding
Why is each bond angle exactly 120 in BCl3? (2 marks) - 3 bonding pairs of electrons - repel equally
Give the name which describes the shape of molecules having bond angles 109. Give an example of one such molecule. (2 marks) - Name: Tetrahedral - Example: CH4, CCl4 etc.
Describe the motion of the particles in solid iodine and in iodine vapour. (3 marks) - vibration - about a fixed print - random
Explain why solid iodine vaporises when warmed gently. (2 marks) - weak intermolecular forces - easily broken
Silver and sodium chloride melt at similar temperatures. Give 2 physical properties of Ag which are different from those of NaCl and give a reason for the difference. (4 marks) - Ag conducts electricity - delocalised electrons OR - Ag is malleable/ductile/soft - planes of atoms slide OR - Ag insoluble in water - not ionic OR - Ag conducts heat - delocalised electrons OR - Ag shines - metallic bonding OR - Ag has a high density - large Ar, closely packed
When considering electron pair repulsions in molecules, why does a lone pair of electrons repel more strongly than a bonding pair? (1 mark) - more compact
Name the type of force that holds the particles together in an ionic crystal. (1 mark) - Electrostatic
What is a covalent bond? (1 mark) - shared electron pair
State how a coordinate bond is formed. (2 marks) - both electrons - donated from the same atom/molecule
What is a permanent dipole? (2 marks) - Charge separation/unequal sharing of electrons - Leading to delta charges
Explain why a molecule of hydrogen chloride is polar? (2 marks) - chlorine is more electronegative then H - attracts electrons towards Cl
Name the type of force that exists between molecules of chlorine. (1 mark) - Van der Waals'
Why is there no hydrogen bonding between molecules of HBr? (1 mark) - Bromine is not sufficiently electronegative/there isn't a large enough electronegativity difference.
By referring to the types of intermolecular force involved, explain why energy must be supplied in order to boil liquid HCl. (3 marks) - Van der Waals' - Dipole-dipole - Energy needed to overcome these forces
State what is meant by the term polar bond. (1 mark) - partial charges on atoms of bond/bonding pair shared unequally
Suggest the strongest type of intermolecular force present in pure sulphuric acid (H2SO4). Briefly explain how this type of intermolecular force arises. (2 marks) - Hydrogen bonding - attraction between delta +ve charge on H and delta -ve charges on O atoms in adjacent molecules
State the bond type in sodium oxide and the bond type in sulphur dioxide. In each case, explain the link between the bond type and the electronegativity of the elements involved. (4 marks) Sodium oxide: - ionic - big difference in electronegativity Sulphur dioxide: - covalent - smaller electronegativity difference
Coordinate bonding can be described as dative covalency. In this context, what is the meaning of each of the terms covalency and dative? (2 marks) - Covalency: shared electron pair - Dative: both electrons from one atom
Why is sodium chloride ionic rather than covalent? (2 marks) - chlorine is more electronegative than sodium - an electron transfers from sodium to chlorine
Why is aluminium chloride covalent rather than ionic? (2 marks) - smaller electronegativity difference - so more equal sharing
Why is molten sodium chloride a good conductor of electricity? (1 mark) - Mobile free ions
Explain, in terms of covalent bonding, why the element iodine exists as simple molecules whereas the element carbon does not. (3 marks) - Carbon forms 4 bonds - give a macromolecule - iodine forms only one bond
Describe the nature and strength of the bonding in solid calcium oxide. (3 marks) - strong - electrostatic attractions - between ions held in a lattice
Use the kinetic theory to describe the changes that take place as calcium oxide is heated from 25 degrees to a temperature above its melting point. (3 marks) - vibrations - increase -as temperature increases until vibrations are so violent that the ions break free at the melting point
State two properties of calcium oxide that depend on its bonding. (2 marks) - high melting point/boiling point - electrical conductivity when molten or in solution
State one feature which molecules must have in order for hydrogen bonding to occur between them. (1 mark) - Hydrogen atom bonded to a highly electronegative atom
Give the name of the type of intermolecular bonding present in H2S, and explain why hydrogen bonding does not occur. (2 marks) - Van der Waals' - Sulphur not sufficiently electronegative
State and explain the similarities and differences in electrical conductivity of sodium, graphite and diamond. (4 marks) - sodium and graphite conduct, diamond does not - delocalised electrons in graphite - diamond as no free electrons - conduction due to delocalised electrons flowing
State which one of the elements neon, sodium, magnesium, aluminium and silicon has the lowest melting point and explain your answer in terms of the structure and bonding present in that element. (3 marks) - neon - free atoms - weak van der Waals' forces
State which one of the elements neon, sodium, magnesium, aluminium and silicon has the highest melting point and explain your answer in terms of the structure and bonding present in that element. - silicon - macromolecular - covalent bonds
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