principles of chemistry

Question 1

2 properties of metals

Answer 1

-basic metal oxides
- conduct electricity

Question 2

2 properties of non metals

Answer 2

-acidic non metal oxides
- don’t conduct electricity

Question 3

definition of ionic bond

Answer 3

strong electrostatic attraction between oppositely charged particles

Question 4

moles, mass and Mr

Answer 4

moles=mass/Mr

Question 5

what charge does silver ion have

Answer 5

+1

Question 6

what charge does copper ion have

Answer 6

2+

Question 7

what charge does iron ion have

Answer 7

2+ or 3+

Question 8

what charge does lead ion have

Answer 8

2+

Question 9

what charge does zinc ion have

Answer 9

2+

Question 10

why do ionic compounds have high mp/bp

Answer 10

1) they have giant ionic structures (so they are held in a closely packed 3D lattice by the attraction between oppositely charged ions)
3) the electrostatic attraction between oppositely charged ions is very strong
4) requires a lot of energy to break these attractions; needs high temperature to melt

Question 11

hydrogen ion

Answer 11

H+

Question 12

hydroxide ION

Answer 12

OH-

Question 13

ammonium ion

Answer 13

NH4+

Question 14

carbonate ion

Answer 14

CO3 2-

Question 15

nitrate ion

Answer 15

NO3 -

Question 16

SULFATE ION

Answer 16

SO4 2-

Question 17

are ionic compounds elctrical conductors?

Answer 17

no- when solid they don’t conduct electricity as there are no free charged particles
yes- when moten/ in aqueous solutions since there are free charged particles

Question 18

define covalent bond

Answer 18

a strong electrostatic attraction between the (negatively charged) shared pair of electrons and the (positively charged) nuclei of the atoms involved

Question 19

why do simple covalent molecules have low melting points?

Answer 19

the forces of attraction between the molecules (intermolecular forces) are very weak, therefore require little energy to overcome

Question 20

what happens in general as the size (relative molecular mass) of the molecules increases

Answer 20

the mp/bp increases since the intermolecular forces get stronger.
this is because there are more points along the larger molecules for intermolecular forces to act between, so more energy is needed to break them

Question 21

why do giant covalent structures have high mp/bp?

Answer 21

1) all the atoms are bonded by strong covalent bonds
2) lots of energy needed to break lots of these bonds

Question 22

3 properties of giant covalent substances

Answer 22

solids with high mp
don’t conduct (except graphite)
insoluble in water

Question 23

explain how the structure of diamond influences its physical properties

Answer 23

1) each carbon atom forms 4 strong covalent bonds so lots of energy is needed to break them => high mp
2) the strong covalent bonds hold them in a very rigid lattice structure, so it is very hard
3) no free electrons so does not conduct electricity

Question 24

explain how the structure of graphite influences its physical properties

Answer 24

1) each carbon atom only forms 3 covalent bonds, creating layers of carbon atoms held together by weak intermolecular forces => the layers can slip over each other so graphite is soft and slippery
2) strong covalent bonds= high mp
3) sea of delocalised electrons (between layers with the 4th electron in carbon’s outer shell) means it conducts electricity

Question 25

explain how the structure of C60 fullerene influences its physical properties

Answer 25

1) although it is a simple molecular substance, the molecules are large so the intermolecular forces are large enough that it is a solid at room temp
2) the molecules are held together by weak intermolecular forces so can slide over each other, so it is soft.
3) each carbon has a delocalised electron but it can’t move between molecules so it is a poor electrical conductor

Question 26

What is lime water

Answer 26

Calcium hydroxide