Module 2

Question 1

Relative Isotopic Mass?

Answer 1

The mass of an isotope of an atoms of an element relative to 1/12 of carbon-12.

Question 2

Relative Atomic Mass

Answer 2

The weighted mean mass of an atom of an element relative to 1/12 of the mass of the carbon-12 atom.

Question 3

How to use a mass spectrometer?

Answer 3

-Place sample in the mass spec
-Sample is vapouriest and then ionised to form positive ions.
-The ions are accelerated. The heavier ions move more slowly and are more difficult to deflect that lighter ions so the ions of each isotope are separated.
-the ions are then detected on the mass spec as a mass-to-charge ratio m/z. The greater the abundance, the greater the signal.

Question 4

What does the Avogadro Constant represent

Answer 4

Number of atoms/particles

Question 5

Relative Formula Mass

Answer 5

Compares the mass of a formula unit with the mass of an atom of carbon-12.

Question 6

What is water of crystallisation?

Answer 6

When crystals have a crystalline structure where they are hydrated.

Question 7

What are the assumptions made when you find the formula of a hydrated salt?

Answer 7

1. All of the water has been lost
2. There was no further decomposition

Question 8

Equation that involves concentration and moles

Answer 8

n = c x V

Question 9

What are the conditions of RTP

Answer 9

20c/ 293 k
101 kPa

Question 10

What is molar gas volume?

Answer 10

Volume per mole of gas molecules at stated temp and pressure.
24dm3mol-1

Question 11

What is the ideal gas equation?

Answer 11

pV = nRT

Question 12

What does ‘R’ stand for in the ideal gas equation?

Answer 12

Ideal Gas constant = 8.31 Jmol-1K-1

Question 13

What is a limiting reagent?

Answer 13

The reactant that is not in excess will be completely used up first and stop the reaction.

Question 14

How is a salt formed?

Answer 14

By a base replacing a H+

Question 15

Atomic Orbitals

Answer 15

A region around the nucleus that can hold up two electrons in opposite spins.

Question 16

How is a covalent bond different to an ionic?

Answer 16

The attraction is localised as it acting solely between the share pair of electrons.

Question 17

Average Bond Enthalpy

Answer 17

A measurement of covalent bond strength.

Question 18

What does a solid line represent in shapes of molecules?

Answer 18

A bond in the plane of the paper

Question 19

A solid wedge?

Answer 19

Bond comes out of the plane of the paper

Question 20

Dotted wedges?

Answer 20

bonds go into the plane of the paper

Question 21

Angle - 109.5. BPs - 4

Answer 21

Tetrahedral

Question 22

Angle - 107 BPs - 3. LPs- 1

Answer 22

Pyramidal

Question 23

Non-linear

Answer 23

2 lone pairs
2 bonds pairs
104.5.
[there 4 pairs overall but two are lone pairs so 109.5 - 2(2.5) as for every lone pair you subtract 2.5 from the angles]

Question 24

Linear

Answer 24

Angle - 180
2 Bond pairs

Question 25

Angle- 120. BPs- 3

Answer 25

Trigonal Planar

Question 26

Octahedral

Answer 26

90 angle
5 bond pairs

Question 27

Why is SF6 an octahedral shape?

Answer 27

This is because the 6 fluorine atoms are positioned at the corners of an octahedron.

Question 28

What is electronegativity?

Answer 28

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

Question 29

Bond Polarity of non-polar bonds.

Answer 29

The bonded electron pair is shared equally, they have the same or similar electronegativity.
The bond is a pure covalent bond.
They don’t mix with water or polar solvents

Question 30

What is polar bond?

Answer 30

A bonded electron pair that is shared unequally between the bonded atoms.
Results in a polar covalent bond.

Question 31

What is a polar molecule?

Answer 31

^A molecule with 2 or more atoms may have 2 or more polar bonds.

Question 32

What are intermolecular forces?

Answer 32

I weak interactions between dipoles of different molecules.

Question 33

Describe induced dipole-dipole interactions [london forces]

Answer 33

They exist between all molecules. They are formed by
- movement of electrons produces changing dipole in a molecule.
-an instantaneous dipole will exist at any moments [its position is always constantly changing]
-the instantaneous dipole induces a dipole on a neighbouring molecule.
-induced dipole will further induce dipoles on other neighbouring molecules.

Question 34

Describe the strength of London forces

Answer 34

The large the induced dipole, the greater the dipole-dipole interactions, and therefore the stronger the attractive force between the molecules.

Question 35

Describe permanent dipoles

Answer 35

A permanent dipole occurs when there is an electronegative atom [so if it is two F atoms it will cancel out and therefore only have london forces and are non-polar].

Question 36

Describe simple molecular substances

Answer 36

Made up of simple molecules
Has a definite molecular formula such as neon, hydrogen and water.
They form a regular structure called a simple molecular lattice. The molecules are held in place by weak intermolecular forces, and covalent bonds are present in between the atoms.

Question 37

Describe hydrogen bonds

Answer 37

A special type of permanent dipoles, that is found in between molecules that are a hydrogen atom attached to an electronegative atom.
The hydrogen bond acts between a lobe pair of electrons on an electronegative atom in one molecule and a hydrogen atom in another molecule.

Question 38

What are anomalous properties of water?

Answer 38

-solid ice is less dense than water, this is because there are more hydrogen bonds holding in the water and therefore are held apart in an open lattice structure, the water molecules in the ice are further apart and so solid ice less dense and floats on water. Four hydrogen bonds can form on a oxygen atom.
- It has a high melting point and boiling point, water has both london forces and hydrogen bonds to overcome and therefore it requires a lot of energy to break them down.
- high surface tension and cohesion
- high viscosity