Definitions

Question 1

What is relative isotopic mass

Answer 1

It is the mass of one atom of the isotope relative to 1/12 the mass of one atom of carbon-12

Question 2

What is relative atomic mass (Mr)

Answer 2

It is the weighted average of the isotopic masses of one atom of an element relative to 1/12 the mass of one atom of carbon -12

Question 3

What is relative molecular mass?

Answer 3

It is the wighted average of the masses of one molecule of a substance relative to 1/12 the mass of one atom of carbon -12.

Question 4

What is relative formula mass?

Answer 4

It is the weighted average of the masses of one formula unit relative to 1/12 the masses of one atom ot carbon -12.

Question 5

What is an empirical formula?

Answer 5

The empirical formula of a compound is the simplest formula that shows the simplest whole number ratio of the atoms of each element present in the compound.

Question 6

What is a molecular formula?

Answer 6

The molecular fermula. of a compound shows the actual number of atoms of each element in one molecule of the compound. It is a simple multiple of the empirical formula and can only be obtained if the molar mass is known.

Question 7

What is 1 mole of a substance?

Answer 7

1 mole of a substance is the amount of that substance which contains 6.02x10^23 particles. [Avogadros constant]

Question 8

What is a disproportionate on reaction?

Answer 8

It is a redox reaction where a single substance is oxidized and reduced at the same time.

Question 9

What is the Manganate titration colour change?

Answer 9

Purple (MnO4-) to colourless (end point) / faint pink (Mn2+)

Question 10

What is the iodine thiosulfate titration color change?

Answer 10

Solution turns pale yellow after addition of starch
Solution turns colourless at end point

Question 11

Basic assumptions when doing ideal gas / kinetic theory of gas ?

Answer 11

1. A gas is composed of tiny particles that have negligible volumes compared to volume of container
2. There are negligible intermolecular forces between gas particles
3. Collisions are perfectly elastic and there is no net loss in Kinetic Energy between gas particles

Question 12

What causes less deviation from ideal gas behavior? (Approaching ideal gas behavior)

Answer 12

1. Low pressure: IMF negligible, total volume of particles negligible
2. High temperature: sufficient KE to overcome IMF attractions: negligible.
   * stronger IMF = stronger deviation
   ** larger molecular mass = stronger id-id

Question 13

What is a metallic bond?

Answer 13

It is the electrostatic forces of attraction between metal cations and the sea of delocalised electron

Question 14

How does metallic bond strength relate to
1. Cations of higher charge
2. Ionic radius

Answer 14

1. Directly proportional (cation higher charge = increased MB strength)
2. Inversely proportional (increased MB strength = smaller ionic radius)

Question 15

What is an ionic bond ?

Answer 15

It is the electrostatic forces of attraction between oppositely charged ions in an ionic compound

Question 16

What is a covalent bond?

Answer 16

It is the electrostatic forces of attraction of the positively charged nuclei of each bonding atom for the shared pair of electrons

Question 17

Define bond energy

Answer 17

It is the energy required to break one mole of covalent bonds between atoms in a gaseous molecule

Question 18

Define bond length

Answer 18

The distance between the nuclei of the two atoms covalently bonded to each other

Question 19

What affects the strength of covalent bonds?

Answer 19

1. Bond order: triple > double > single
2. Effectiveness of orbital overlap: decreases with larger atomic size (Mr)

Question 20

Describe diamond’s structure and bonding

Answer 20

Each carbon atom forms strong covalent bonds with 4 carbon atoms in a 3D tetrahedral arrangement in a giant covalent lattice structure

Question 21

Describe graphites structure and bonding

Answer 21

Each carbon atom forms strong covalent bonds with 3 other carbon atoms in a 2 D layer of hexagonal carbon rings with weak intermolecular forces of attraction between graphene layers + electric conductivity from highly mobile pi electrons

Question 22

Factors affecting strength of id-id

Answer 22

1. Size of electron electron cloud (ease of distortion) : larger Mr = larger cloud, dipoles more easily induced, more energy to overcome stronger id-id
2. Surface area of contact: straight chain have larger surface area of contact

Question 23

3 atoms that can have hydrogen bonding (IMF)

Answer 23

N, O, F
* protonic H / lone pair

Question 24

Factors that affect hydrogen bonding strength

Answer 24

1. Different number of H-bonds: more protonic H or lone pairs on NOF
2. Polarity of H-(NOF) bond: more polar = stronger. Order: N<O<F
3. Infra molecular H bonding may reduce the number of available H bonding sites for intermolecular bonding

Question 25

What does the bond strength of ionic, metallic, and covalent bonds depend on?

Answer 25

Ionic: L.E.
Metallic:
1. No. Of electrons that can be delocalised
2. Inversely proportional to ionic radius
Covalent:
1. Bonds: Effectiveness of orbital overlap (dependent on atomic radius / Mr) & bond order (1-3)
2. IMF: id-id, pd-pd, h bonding (broken in heating)