exam questions

Question 1

A student uses paper chromotography to investigate the dyes in 5 different inks

describe how the student should set up and carry out her experiment

Answer 1

1) put separate spots of each inks on the line
2) pour some solvent into the bottom of the beaker
3) place the paper in the beaker so that the spots are above the level of solvent
4) leave until the solvent has risen up the paper near the top

Question 2

explain how using the cotton wool increases the accuracy of this investigation

Answer 2

1) to stop acid leaving the flask
2) without cotton wool mass lost would be too large.

Question 3

explain using the particle collision theory how increasing the concentration of the acid would affect the rate of reaction.

Answer 3

1) rate increases
2) more particles in the same volume
3) more successful collisions per unit of time

Question 4

explain using the particle collision theory how increasing the temperature would affect the rate of reaction

Answer 4

1) the rate increases
2) mean kinetic energy of particles increases
3) more successful collisions per unit of time

Question 5

Describe a method that she could use to prepare a dry sample of magnesum nitrate crystals from magnesium oxide

Answer 5

1) heat the acid in a beaker
2) add magnesium oxide
3) stir
4) filter to remove excess magnesium oxide
5) heat magnesium nitrate solution
6) until crystals form in a cooled sample
7) leave solution to crystallise

Question 6

explain with refernece to structure and bonding why diamond has a high melting point

Answer 6

1) covalent bonds are strong
2) many covalent bonds need to be broken
3) a large amount of energy is needed to break these bonds.

Question 7

explain why c60 fullerene has a much lower melting point than diamond

Answer 7

1) the intermolecular forces of attraction are weak
2) therfore less energy is needed to overcome the forces

Question 8

c60 fullerne is used by doctors when injecting medicines into their patients.

suggest why c60 fullerene is suitable for this purpose

Answer 8

• it wont react with the blood/medicine

Question 9

explain why graphite is soft and conducts electricity

Answer 9

1) the structure is in layers
2) there are weak forces of attraction between the layers
3) layers can slide over each other
4) each carbon atom is bonded to three other carbon atoms
5) one delocalisd electron per carbon atom
6) delocalised electrons flow through the structure

Question 10

identift a gas produced by the thermal decomposition of calcium carbonate

Answer 10

carbon dioxide

Question 11

state an environmental problem caused when sulfur dioxide gas dissolves in water in the atmosphere

Answer 11

acid rain

Question 12

name the process used to coat iron with zinc

Answer 12

galvanising

Question 13

give the common name for this brown solid

Answer 13

rust

Question 14

give the name of the two substances that react with the iron to borm the brown solid

Answer 14

1) oxygen
2) water

Question 15

state the meaning of the term ionic bond

Answer 15

The electrostatic attraction between oppositely charged ions, strongly attached together

Question 16

describe the test for carbon dioxide gas

Answer 16

• limewater
• limewater turns cloudy

Question 17

explain why carbon dioxide turns from a solid to a gas at a very low temp

Answer 17

1) it has weak intermolecular forces
2) little energy needed to overcome the intermolecular forces

Question 18

diamonds are used in cutting tools
graphite is used in pencils to make marks on paper

explain with reference to structure and bonding, why each substance is suitable for its particular use

Answer 18

1) in diamond each carbon atom is covalently bonded to four other carbon atoms
2) in a tetrahedral lattice
3) the covalent bonds are very strong
4) therefore diamond is hard and good for cutting tools
5) in graphite, each carbon atom is covalently bonded to three other carbon atoms
6) the structure is in layers
7) weak forces between layers
8) therefore the layers slide over each other
9) this makes graphite soft

Question 19

suggest why the student measures the mass of the spirit burner and fuel immediately after heating the water

Answer 19

to make sure that any mass doesn’t get lost due to heat loss.

Question 20

when fuel is burned, the student notices that a black solid forms on the bottom of the copper can.

identify the black solid

Answer 20

carbon

Question 21

explain why carbon forms

Answer 21

1) incomplete combustion
2) oxygen supply is limited

Question 22

why is the experiment carriesd out in a polystyrene cup

Answer 22

1) a good insulator
2) prevents heat loss