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Chemistry (RM) > C6 Shapes Of Molecules And Intermolecukar Forces > Flashcards

C6 Shapes Of Molecules And Intermolecukar Forces Flashcards

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1
Q

6.1 - what is the electron pair repulsion theory?

A

An electron has a negative charge, so electrons repel one another.This theory explains and predicts shapes of molecules and polyatomic ions

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2
Q

What do the electron pairs surrounding a central atom determine?

A

The shape of the molecule or ion

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3
Q

Why do electron pairs repel one another?

A

Due to their negative charges, so they’re arranged far apart as possible

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4
Q

Are lone electron pairs closer or further from the central atom?what does this mean?

A

Closer, the lone pair repels more strongly compared to a bonded pair

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5
Q

What happens to the bond angle because lone pairs repel bonded pairs closer together

A

Decrease by 2.5*

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6
Q

What are the characteristics of a tetrahedral

A

4 areas of electron density, no lone pairs, bond angle 109.5

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7
Q

Characteristics of a pyramidal

A

4 areas of electron density, 1 line pairs, bond angle 107

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8
Q

Non-linear characteristics

A

4 areas of electron density , 2 line pairs, bond angle 104.5

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9
Q

Linear characteristic

A

180 bond angle, no line pairs,

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10
Q

Trigonal planner

A

120, 3 electron pairs, no lone pairs

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11
Q

Trigonal by-pyramidal

A

5 areas of electron density, 90 and 120, no line pairs

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12
Q

Octahedral

A

6 areas of electron density, no line pairs, 90 degrees bond angle

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13
Q

6.2 - in what bond are the nuclei of the bonded atoms attract the shared pair of electron?

A

Covalent

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14
Q

What is electronegativity?

A

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

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15
Q

How is electronegativity measured?

A

The Pauling scale - higher value=higher electronegativity

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16
Q

What is the correlation between Pauling scale and electronegativity?

A

Increased electronegativity up and across the periodic table

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17
Q

State the bond types and the electronegativity differences

A

Covalent-0
Polar covalent-0-1.8
Ionic- >1.8

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18
Q

In a non-polar bond, the bonded electron pair is shared…

A

Equally

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19
Q

A bond will be non-polar when

A

The bonded atoms are the same or the bonded atoms have the same or similar electronegativity

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20
Q

In a polar bond, the boned electron pair is shared…

A

Unequally

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21
Q

A bond will be polar when

A

The bonded atoms are different and have different electronegativity values

22
Q

What is a dipole?

A

The separation between opposite charges (delta negative and positive)

23
Q

What is a permanent dipole

A

A dipole in a polar covalent bond that does not change

24
Q

H2O is polar, why?

A

Because there at different bonded atoms, with different electronegativity values, with permanent dipoles that do not cancel out

25
Q

CO2 is non-polar, why?

A

Because the bonded atoms have similar electronegativity, dipoles cancel out each other, and two different bonded atoms are bonded.

26
Q

What happens when a substance dissolves?

A

The positive ions are surrounded by the negative oxygen from the H2O molecules.
The negative ions are surrounded by the positive hydrogen ions from the H2O molecules.

27
Q

What is a polar covalent bond?

A

Shared pair of electrons where the electron pets not shared equally between the two bonded atoms

28
Q

6.3 - compared to covalent bonds, what are intermolecular forces?

A

They are weak interactions between dipoles of different molecules

29
Q

What are the different types of intermolecular forces?

A

Induced dipole dipole interactions(London forces)
Permanent dipole dipole interactions
Hydrogen bonding

30
Q

What are intermolecular forces responsible for and what do covalent bonds determine?

A

Intermolecular forces are responsible for physical properties such as melting and boiling point
Covalent bonds to the identity and chemical reaction of molecules

31
Q

State in order of smallest largest bond with the bond strength

A

London forces
Permanent dipole dipole interactions
Hydrogen bonds
Single covalent bonds

32
Q

What are induced dipole dipole interactions (London forces)

A

Weak into molecular forces that exist between all molecules where the polar or nonpolar They act between induced dipoles in different molecules

33
Q

State how induced Dipod dipole interactions occur

A

Movement of electrons produce a changing dipole in a molecule
At any instant, instantaneous dipole will exist, but its position is constantly shifting
The instantaneous dipole induces of a neighbouring molecule
Induced dipole induces further on neighbouring molecules which then attract one another

34
Q

In London forces the more electrons in each molecule

A

The larger the instantaneous and induced dipoles
The greater than induced dipole dipole interactions
The stronger the attractive forces between molecules

35
Q

What are permanent dipole dipole interactions?

A

They are interactions that act between permanent dipole in different polar molecules
Such as HCL and HCL
The positively charged each from one molecule is attracted to negative CL in the other molecule

36
Q

What are central molecular substances?

A

They are made up a simple molecules which are small units containing a defined number of atoms within a definite molecular formula

37
Q

In the solid state, simple molecules from a regular structure are called simple molecular lattice in these lattes. What are the molecules held by? And are the atoms within each molecule bonded by?

A

They held by week into molecular forces and the atoms within each molecule are bonded together strongly by covalent bonds

38
Q

What are the properties of simple molecular substances?and why?

A

Low melting point and low boiling points

This is because the week in molecular forces can be broken by very very little energy

39
Q

When a simple molecular latter is broken apart during melting, what does and what does not break

A

Only the week into molecular forces break and the covalent bonds are too strong and do not break

40
Q

What two categories do the solubility of covalent substances with simple molecular structures fall into ?

A

Polar and non-polar

41
Q

What happens when a simple molecular compound is added to a non-polar solvent?

A

The intermolecular forces formed between the molecules and the solvent
The interactions weak and the intermolecular forces in the simple molecular lattice so the intermolecular forces break and the compound dissolves

42
Q

Nonpolar simple molecular substances tend to be soluble in nonpolar solvent because the interactions weaken the intermolecular forces in the simple molecular lattice so therefore the compound dissolves

A

Simple molecular substances tend to be insoluble in polar solvent because the intermolecular bonding within the polar solvent is too strong to be broken This is because there is little interaction between the molecules in the lattice and the solvent molecules

43
Q

The solubility depends on the strength of the dipole and can be hard to predict. Some compounds contain both polar and nonpolar parts in their structure so they can dissolve in both polar nonpolar solvent.what happens in biological molecules?

A

Some biological molecules have hydrophobic and hydrophilic parts The hydrophilic parts will be polar and contain electronegative atoms that can interact with water

44
Q

Why is there no electrical conductivity in simple molecular structures?

A

Because there are no mobile charged particles in simple molecular structures so therefore with no charge particles that can move there is nothing to complete the electrical circuit

45
Q

6.4 - what is a hydrogen bond?

A

It is a type of permanent dipole dipole interaction found between molecules containing an electronegative atom with a lone pair of electrons and a hydrogen atom attached to an electronegative atom

46
Q

Are hydrogen bonds the strongest or weakest into molecular attractions?

A

Strongest

47
Q

Why is the solid state of water less dense than the liquid state?

A

Ice is less dense than water because the hydrogen bonds hold the water molecules apart in an open lattice structure
The water molecules in is further apart than in water
Solid is less than liquid water and floats

48
Q

What does the floating ice provide?

A

It forms an insulating layer and preventing the wood from freezing solid so therefore organisms that live in water able to survive

49
Q

What decreases the density of the water when it freezes?

A

The holes in the open latter structure

50
Q

Why does water have a high melting and a high boiling point?

A

Because the Hodgen bonds are extra forces over and above the London forces so therefore more energies needed to overcome these bonds

51
Q

At room temperature and pressure if there were no hydrogen bonds what would happen to life on earth?

A

There would be no life on earth because there would be no liquid water

52
Q

What are anomalous properties of water are there because of hydrogen bonds?

A

Water has a high surface tension and viscosity and cohesion which results in water droplets

Chemistry (RM) (1 decks)

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