Chapter 6

Question 1

How do electron pairs around central atom determine the shape

Answer 1

Electrons repel so they are arranged as far apart as possible to minimise repulsion and have a definite shape

Question 2

3d shape of compound

What does solid line mean

Answer 2

Bond on the plane of paper

Question 3

3d shape of compound

What does a solid wedge mean

Answer 3

Bond comes out of the plane of paper

Question 4

3d shape of compound

What does a dotted wedge mean

Answer 4

Bond goes into plane of paper

Question 5

Why does lone pair repel more strongly than bonded pair

Answer 5

Slightly closer to central atom and occupies more space

Question 6

Which repels more: bonded and lone or bonding and bonding?

Answer 6

Bonded and lone repels most

Question 7

How much is the angle decreased for each lone pair in compound

Answer 7

2.5 degrees

Question 8

Shape and angle of H2

Answer 8

Linear

180 degrees

Question 9

Shape and angle of CO2

Answer 9

Linear

180 degrees

Question 10

Shape and angle of BF3

Answer 10

Trigonal planar

120 degrees

Question 11

Shape and angle of CH4

Answer 11

Tetrahedral

109.5 degrees

Question 12

Shape and angle of PCl5

Answer 12

Trigonal bipyramid

90 and 120 degrees

Question 13

Shape and angle of SF6

Answer 13

Octahedral

90 degrees

Question 14

Shape and angle of H3O +

Answer 14

Pyramidal

107 degrees

Question 15

Shape and angle of H2O

Answer 15

Non linear

104.5 degrees

Question 16

What is electronegativity

Answer 16

Amount of attraction of a bonded atom for the pair of electrons in a covalent bond

Question 17

What is a pure covalent bond and example

Answer 17

H2

Equal electronegativity so electrons shared equally in bond

Question 18

Why does electronegativity change

Factors that affect it is…

Answer 18

Nuclear charge are different meaning number of proton

Different size of atom so larger the size weaker attraction to outer shell where there will be a bond

Question 19

Which atom would the shared electrons be closer to in HCl

Cl is more electronegative

Answer 19

Cl

Question 20

Where does electronegativity increase according to Pauling scale in periodic table

Answer 20

Increases up the table

Increases from left to right of table so across

Question 21

What is the meaning of non polar bond

Answer 21

Pair shared equally between bonded atoms that have similar or same electronegativities

Question 22

What is a dipole

What does it mean by Cl end having a delta negative in HCl

Answer 22

It is a separation of opposite equal charges

Small partial negative charge

Question 23

What is a permanent dipole

Answer 23

Dipole in polar covalent bond does not change

Question 24

What is a polar molecule

Answer 24

Molecule with permanent dipoles and the shape is not symmetrical so the charges don’t cancel out
And there is an overall dipole

Question 25

CO2 has permanent dipoles but it is classified as non polar | Why

Answer 25

Shape is symmetrical so dipoles cancel each other out

Question 26

What shapes are symmetrical 4 points

Answer 26

Linear Trigonal planar Tetrahedral Octahedral

Question 27

How do polar compounds dissolve in water

Answer 27

Water surrounds lattice Positive ion or delta positive attracted to O part of water Negative part attracted to H This attraction pulls and breaks the lattice and dissolves

Question 28

Finish Greater the difference in electronegativity the …. The permanent dipole

Answer 28

Greater

Question 29

What are the three types of intermolecular forces

Answer 29

Induced dipole dipole interactions (London forces) Permanent dipole dipole interaction Hydrogen bond

Question 30

What are the van der waals forces

Answer 30

Induced dipole dipole interactions (London forces) | Permanent dipole dipole interaction

Question 31

What type of molecules do London forces work

Answer 31

All molecules | Polar and non-polar

Question 32

How are London forces made

Answer 32

Fluctuations of electrons produce a changing dipole in molecule and at any moment an instantaneous dipole will exist temporarily. This instantaneous dipole induces neighbouring molecules And then there will be small attractions for an instant

Question 33

How does number of electrons affect induced dipoles

Answer 33

More electrons mean larger instantaneous and induced dipoles, greater the induced dipole dipole interactions and stronger attractive force between molecules

Question 34

What type of molecule do permanent dipole dipole interactions occur

Answer 34

Between different polar molecules

Question 35

Which usually has a higher mp/bp Polar or non polar? Why?

Answer 35

Polar as it has both permanent and induced interactions | Non polar only has induced interactions so more intermolecular forces and more energy required to break all of this.

Question 36

When does hydrogen bonding occur? What is it? | What atoms must or can be present?

Answer 36

Strong dipole dipole interaction between an electron deficient H atom and a lone pair of electrons on a highly electronegative atom on a different molecule. H atom and (O, N, F)

Question 37

Ice is less dense than liquid water | Why?

Answer 37

Hydrogen bonds holds water molecules apart forming an open lattice structure of ice

Question 38

Features of water that are unusual compared to other similar molecules (because of H bonds) 2 points

Answer 38

High mp/bp as H bonds along with other intermolecular forces must be broken and require more energy H bonds give water high surface tension and viscosity as H bonds pull molecules together (attractive force)