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Chemistry A-Level OCR > MODULE 2: Shapes of Molecules and Intermolecular Forces > Flashcards

MODULE 2: Shapes of Molecules and Intermolecular Forces Flashcards

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1
Q

How many degrees does the bond angle in a covalent bond decrease per lone pair of electrons?

A

2.5 degrees

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2
Q

What is the bond angle in a covalent bond with 4 bonded pairs?

A

109.5 degrees

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3
Q

What is the bond angle in a covalent bond with 3 bonded pairs and 1 lone pair?

A

107 degrees

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4
Q

What is the bond angle in a covalent bond with 2 bonded pairs and 2 lone pairs?

A

104.5 degrees

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5
Q

What is the bond angle in a covalent bond with just 3 bonded pairs and no lone pairs?

A

120 degrees

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6
Q

What is the bond angle in a covalent bond with 6 bonded pairs and no lone pairs?

A

90 degrees

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7
Q

What is the name of a covalent bond with 4 bonded pairs?

A

Tetrahedral

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8
Q

What is the name of a covalent bond with 3 bonded pairs and 1 lone pairs?

A

Trigonal pyramidal

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9
Q

What is the name of a covalent bond with 2 bonded pairs and 2 lone pairs?

A

Non-linear (because they’re bent!)

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10
Q

What is the name of a covalent bond with 3 bonded pairs and no lone pairs?

A

Trigonal planar

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11
Q

What is the name of a covalent bond with 6 bonded pairs and no lone pairs?

A

Octahedral

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12
Q

Why do lone pairs cause more repulsion?

A

Because they are not shared, therefore have a more concentrated negative charge

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13
Q

When drawing 3D molecules, what does a solid line represent?

A

A bond on the same plane as the paper

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14
Q

When drawing 3D molecules, what does a solid wedge represent?

A

A bond that comes forward from the plane of the paper (towards you)

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15
Q

When drawing 3D molecules, what does a dotted wedge represent?

A

A bond that goes away from the plane of the paper (away from you)

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16
Q

What is electronegativity?

A

The ability of an atom in a covalent bond to attract the bonded pair of electrons

17
Q

How does electronegativity increase across the periodic table?

A

Up and to the right (towards fluorine)

18
Q

How is electronegativity measured?

A

Pauling electronegativity scale (0.0-4.0)

19
Q

What is a polar bond?

A

A bond where the shared pair of electrons is unequally distributed as the atoms sharing the bonds have different electronegativity values

20
Q

What is a non-polar bond?

A

A bond where the shared pair of electrons is shared equally between atoms

21
Q

What happens to the atoms with a polar bond?

A

They gain partial charges

22
Q

What symbol is used to represent partial charges?

A

Delta (δ)

23
Q

What are the partial charges in a polar bond called?

A

Permanent dipoles

24
Q

What are the different types of intermolecular forces?

A

London forces, permanent dipole-dipole interactions, hydrogen bonding

25
Q

What are London forces?

A

Weak intermolecular forces that exist between all molecules, occur due to movement of electrons around the nucleus (temporary)

26
Q

How does the strength of London forces change?

A

Increases as number of electrons increases

27
Q

What are simple molecular substances?

A

A substance made up of simple molecules (diatonic molecules) and only have London forces (H2, I2, etc)

28
Q

What are the properties of simple molecular substances?

A

Low melting and boiling points, no conductive

29
Q

What is the solubility of non-polar simple molecular substances?

A

Soluble in non-polar solvents, (tend to be) insoluble in polar solvents

30
Q

What is the solubility of polar simple molecular substances?

A

May dissolve in polar solvents, solubility depends on strength of dipole (stronger dipole = more soluble)

31
Q

What is a hydrogen bond?

A

A form of permanent dipole-dipole interaction that involves an electronegative atom with a lone pair of electrons (oxygen, nitrogen, fluorine) and a hydrogen attached to an electronegative atom with a lone pair of electrons

32
Q

How are hydrogen bonds represented in diagrams?

A

Dashed lines

33
Q

What are the anomalous properties of water?

A

Solid is less dense than liquid form, has a relatively high melting and boiling point

34
Q

Why is water less dense as a solid (ice)?

A

Hydrogen bonds hold water molecules in a lattice structure, so therefore the water molecules are ‘pushed’ further apart and ice expands, increasing the volume but maintaining the same mass (density is mass/volume). This causes ice to float)

35
Q

Why does water have a relatively high melting/boiling point?

A

Because of the stronger hydrogen bonds require more energy to break

Chemistry A-Level OCR (29 decks)

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